E34 M50 thermostat (75 vs 88 Celsius) experience

[ktteoh]

folks, i like to know if anyone has run a lower temp thermostat i.e. 75 degrees Celsius vs the normal 88 degree version.

is it better for engine parts as the heat stress is less?

i'm looking at an ebay item but the brandname is wahler which i'm not familiar with - any opinions on this brand?

http://cgi.ebay.com/ebaymotors/BMW-75-Degrees-Thermostat-E30-E34-318is-318ic-525i_W0QQcmdZViewItemQQcategoryZ33604QQihZ019QQite mZ8038833377QQrdZ1QQsspagenameZWD1V

[632 Regal]

you will get more wear with a cooler stat, your engine was designed for the proper temperature.

[pingu]

And you'll probably lose some fuel efficiency too.

[SnakeyesTx]

HUGE misconception on lower temperature thermostats.

Lower the number doesn't mean cooler running. It means it opens at a lower temperature. When it does that, the coolant in the radiator doesn't get as much time to cool off since its constantly cycling with the thermostat opening more often. Inevidably, you're going to end up running hotter than normal since the coolant has less time to cool down in the radiator.

Stick with what it came with. If you want to run a little cooler, run Red Line's Water Wetter or Royal Purple's Purple Ice. Those actually work. (in my case about 10-15 degrees difference on my old big blocks) Your results may vary a little depending on geography, and engine and driving behavior.

[yaofeng]

HUGE misconception on lower temperature thermostats.

Lower the number doesn't mean cooler running. It means it opens at a lower temperature. When it does that, the coolant in the radiator doesn't get as much time to cool off since its constantly cycling with the thermostat opening more often. Inevidably, you're going to end up running hotter than normal since the coolant has less time to cool down in the radiator.

Stick with what it came with. If you want to run a little cooler, run Red Line's Water Wetter or Royal Purple's Purple Ice. Those actually work. (in my case about 10-15 degrees difference on my old big blocks) Your results may vary a little depending on geography, and engine and driving behavior.

This runs againt experience and also physics. Let's say you remove the thermostat so there is an open hole on the extreme side. Your engine will be running very cool because more coolant is now flowing through the radiator.

Do you have a car, any car, with a stuck open thermostat? The car will be running very cool. Cool to the point you won't get heat in the cabin during winter time in some cases.

[SnakeyesTx]

Have you ever crept along on a 130+ degree beach at less than 5 mph in 4-wheel low with no thermostat? Sure it runs initally cool for a while, but the coolant is constantly moving and never has enough time to sit in the radiator to cool down and cycle through the block. Inevidably you overheat.

That's exactly what a thermostat wsa designed for. To contain the water in the radiator long enough to cool off, and to open when the water in the block exceeds the rating given to open. Without it, it just cycles until it eventually overheats. Maybe if you're driving short distances or moving all the time to have air passover the radiator a lot this would negate overheating, but the fact of the matter is, that with no delay for cooling, it never gets a chance to dissipate the heat.

[yaofeng]

Have you ever crept along on a 130+ degree beach at less than 5 mph in 4-wheel low with no thermostat? Sure it runs initally cool for a while, but the coolant is constantly moving and never has enough time to sit in the radiator to cool down and cycle through the block. Inevidably you overheat.

That's exactly what a thermostat wsa designed for. To contain the water in the radiator long enough to cool off, and to open when the water in the block exceeds the rating given to open. Without it, it just cycles until it eventually overheats. Maybe if you're driving short distances or moving all the time to have air passover the radiator a lot this would negate overheating, but the fact of the matter is, that with no delay for cooling, it never gets a chance to dissipate the heat.

Just look at what you are saying. You are suggesting (no you are saying) a cooler thermostat will make the engine run hotter eventually. Do you really believe that? If that is true, the thermostat manufacturer will be sued to bankruptcy.

We all know cooler thermostat opens earlier to allow more coolant flow at lower temperature to the radiator, thus making the engine run cooler. -30degree F ambient or 130 degree F ambient doesn't make a difference. The heat produced by the pistons will make the coolant much hotter.

[gmannino]

I've heard a technique is also to drill a small hole in the thurmostat. What is this used for and what are its benefits

[Blitzkrieg Bob]

when you bleed the system.

[tdgard]

I could give you my current thermostat. It stuck open about 2 weeks ago. Have not left the blue except when sitting on the highway--then it gets to the first mark--barely. As for this overheating muck--all I can say is my commute is 38 miles each way into the heart of downtown Atlanta. 1 to 1.5 hours each way every day--sure have not seen these supersaturated temps though.

[SnakeyesTx]

No, what I'm saying is that when an engine is given a 170 degree thermostat from the factory, it was meant to be used for factory tune. When the engine coolant temperature exceeds this, the thermostat opens and the hot coolant is expelled thru the top of the radiator and bled down, while the cooler coolant in the radiator gets to pass into the block. This cycle repeats itself every time the temperature exceeds the indicated temperature. In extreme cases the thermostat never gets a chance to close, and usually overheating occurs since the coolant never gets to sit in the radiator for a long enough time to dissipate the heat through the air passing through it via driving and the fans.

When a lower temperature thermostat is installed, what you're effectively doing is lowering the threshold for the termostat to stay closed, and shortening the time allowed for the radiator to do its job. In extreme situations (lets just say A/C on max and stuck in traffic for an hour with an automatic transmission), you will overheat because eventually the fan wont be able to keep up with the heat generated by the engine constantly chugging at idle, the transmission baking in stop and go traffic, and the water constantly moving which has already had its boiling point significantly raised due to being underpressure and constantly in motion causing even more fluid-resistance (try moving your hand around in a hot bath tub and you'll notice how much hotter it feels than just leaving it sit still).

Not running a thermostat at all can do several things as well. If your housing is installed with a thermostatic switch, this will effect the temperature driven vacuum valve obviously. Also some computer controlled engines are very particular about the operating temperature for several sensors that control fuel and spark. Running too cool, too hot, or no thermostat at all can greatly reduce power and economy (this I'm sure you already know).

Now, take the car with no thermostat, automatic slushbox, a/c on max, 100 degrees outside, 140 degree reflective road heat, stuck in traffic doing 2 mph and stopping every 10 feet for an hour (this is a common rush-hour drive for me!). Your radiator gets bombarded with stale air since you're not moving, maybe in an extreme case by hot exhaust firing back at you from the car in front if you like to tailgate. Your electric fan is probably constantly running to keep up since the thermostatic switch controlling it is pegged from the motor heating up, and the whole time your temperature needle slowly starts to climb and never really stops until you finally get up to speed again. By this time your engine computer probably decided that its running too lean, retards the timing, and richens the fuel mixture, and you may or may not notice the smell due to everyones exhaust around you.

Believe me, I used to think the cooler t-stat was the right way to go to, but I've raced, I've 4-wheeled, rock-climbed, mud-bogged, and have been stuck in traffic. It eventually runs hotter every single time in every single application. This was done with a B13 Rotary Engine, a 4.2 I-6 Jaguar, a 258ci (4.2L) AMC Jeep, a 360ci (5.9L) AMC, a 413ci (6.7L) AMC with aluminum heads and intake, several 350ci (5.7L) Chevy's of various tunes and alloys, a 383ci stroker from my 68 Chevelle SS, several 3.8L series 3800 V6's, and most recently my 2.5 in the 525 (though it died before I could tinker with it).

I'm not trying to start a war here, but really the best way to keep cool is just up the output quality of the fan, make sure your shroud is in good shape, and use the water catalysts. The factory tune temperature T-stat is in there for a reason, and most respectable shops will tell you the exact same thing I have (my shop foreman was the person who actually drew it out for me many years back).

[Blitzkrieg Bob]

no thermostat?

Beware...some motors have a dual action T stat.

they don't just restrict the flow, they open and close a bypass port too.

removing it esentally bypasses the flow to the radiator. coolant just goes around & around in the block.

Mazda rotary and the M20 and maybe a few others too.

I'll be checking out my M50TU soon...lazy T stat

[tnt525i]

whoa,, and i thought i did a great thing by using thelower temp thermostat in my car

[stu1]

You should really stick to the factory specified thermostat temperature. It is matched to the radiator, fan, fan clutch, water pump etc.

Changing thermostat temperature may also have an effect on the ECU which may be looking for a certain water temperature.

Stu.

[ktteoh]

folks, the info so far has been confusing. i lived in the hot tropics (malaysia) and have a lot of stop-go traffic in city condition. my intent is that the 75 degree thermostat would reduce the heat stress on the engine block, radiator and all the rubber hoses etc.

here's what i can summarize:

1. some members here have installed the 75 degree thermostat - can they share their experience

2. does someone has a diagram of how a M50 thermostat works (and whether it closes a bypass channel as well)?

3. would it be true that a stuck open thermostat be an extreme case of colder thermostat - who have an experience of such a case?

[DaveVoorhis]

3. would it be true that a stuck open thermostat be an extreme case of colder thermostat - who have an experience of such a case?
I do, though I did not examine the old 'stat to see whether it was really permanently stuck open, closed but opening at too low a temperature, or what.

When idling or driving in stop-and-go traffic (but not particularly hot ambient temperatures, only approx 20 degrees C) the temperature gauge reached the centre line. On the motorway, the gauge dropped to half way between the top of the blue region and the centre line.

[tdgard]

3. would it be true that a stuck open thermostat be an extreme case of colder thermostat - who have an experience of such a case?

Errr...See my post above. Just changed it out tonight & one of the tabs that hold the spring in place had snapped giving me a not quite open or closed stat.

Damnit if I didn't break the bleed screw though.

[ktteoh]

folks, another question i have - someone mentioned a tip about drilling a hole in the thermostat for bleeding purposes - is there a diagram to show me where to drill the hole (what size) and would it weaken the structure of the thermostat (i.e. cause it to rust or crack etc)?

[shogun]

The last time I drilled a hole in the t-stat in a BMW was many years ago when I had a 2002, but only because the t-stat was broken and it was a temporary solution.

Since then I never had the need to do this, but some people here do it.

According to archives:
"drill about a 1/16" hole where the arrow thats supposed to point up is on the new thermostat, this kills the air bubble that collects in the block and allows it to fill with coolant with little to no trouble"

[R1daveg]

Yaofeng - sorry but Snakeeyes is 100% right.
A cooler thermostat open earlier. As long as you have enough airflow through the rad to reduce the incoming water temp to less than what is in the engine already, the engine temp will be lower.
It all comes back to a simple q.. why do you think u have a better idea than the engineering team of BMW? They did the work, leave it alone.

[yaofeng]

Yaofeng - sorry but Snakeeyes is 100% right.
A cooler thermostat open earlier. As long as you have enough airflow through the rad to reduce the incoming water temp to less than what is in the engine already, the engine temp will be lower.
It all comes back to a simple q.. why do you think u have a better idea than the engineering team of BMW? They did the work, leave it alone.

No. He is wrong. And you are too.

I am not arguing the point of using a cooler thermostat on the BMW 2.5 liter engine designed to operate at a set temperature. I would not change it, or alter the operating condition which may increase wear, for instance, among other deleterious effects.

I am arguing in general terms a cooler thermostat makes the engine run hotter. This is plain illogical.

It is mind boggling that you think it works that way. Both of you.

[SnakeyesTx]

Well, I'm so sorry that you can't understand the simplest of logics. I also reiterated that I didn't want to start a war, but apparently you can't understand that either. Furthermore this is my last post on the matter. Apparently its a battle of who can't be wrong which is absolutely ridiculous.

-Edit : You know what.. forget it, I'm wrong... you win... now grow up.-

I'll leave this thread with some good info from another forum.

http://www.mustangforums.com/m_2093594/printable.htm

Read around a bit and you'll see some good points such as :

- a thermostat is basically a regulator for engine warm-up

-a 180 degree thermostat doesn't mean you're going to run at 180 degrees (my favorite point)

- your engine can be overcome by the rate its heating up than the radiator can dissipate and having the thermostat pop open earlier may leave it open 100% a lot sooner thus not letting the radiator dissipate the heat at an equal rate to the engine producing it

- extreme cases (110 degrees used here) can easily overcome the cooling system, which is kinda funny because here in Texas its about 95-105 degrees for almost 7 months out of the year and the absorbed road heat easily exceeds 140. Tie this with the previous note about the t-stat staying open earlier and unable to dissipate the heat in ample time.

- lower economy and sensor issues

...and so on and so forth. I don't need to repeat what's already written there. I'm not an advocator of bad advice, and when asked what would you do, I will NOT be told I'm wrong when I have first hand experience, let alone have done countless repairs professionally. I tried both instances. I've used colder temperature thermostats, and I've used stock application ones as well. Unforunately I live somewhere where the "extremes" are almost a daily occurence with the heat and traffic. I don't question the concept of it opening and cycling more often, but if you're not dissipating the heat, more often isn't worth a hill of beans.

Here's another tidbit : Source : http://www.centuryperformance.com/coolingsys.asp

In this system, the coolant is circulated by the water pump, and the thermostat controls the temperature. The thermostat is closed when the engine is cold, allowing coolant to circulate ONLY in the engine block, bypassing the thermostat and radiator. This allows the engine to warm up faster and uniformly so that "hot spots" are eliminated. When the warming coolant reaches the thermostat, the thermostat will begin to open and allow coolant to pass to the radiator. The hotter the coolant gets, the more the thermostat opens, allowing more volume of water to pass to the radiator. The thermostat also controls the length of time that the coolant remains in the radiator so that the heat is dissipated effectively.

More : Modified Applications : http://1968firebird.org/jharticles/jharticles11.htm

As the performance of my wagon was increased and different parts were tried, the wagon ran hotter on the open road. A large radiator from a Chevy 454 was adapted, and it helped some. A new quality temperature controlled clutch was installed with the fan that helped some. The engine has always been highly tuned and very efficient, so that was not a fixable item. I saw an add for the high flowing Robertshaw thermostat and tried it: That was the real key for me because the engine ran HOTTER with it. I then recognized that I need to slow down the water flow to allow better water distribution in the radiator thus utilizing it’s larger capacity, and longer time in the radiator to improve heat radiation. The addition engine RPM caused by my 3.55 gear, slightly looser converter, and higher engine output all contributed to the problem.


Give me enough time, and I can find examples like this ALL DAY long :p

[31Hertz]

I can't vouch for the overheating thing, but it does make sense in an "ok I guess" kind of way. I tried a lower temp thermostat in my 1991 Chevy Blazer 4.3l V-6 tbi w/auto tranny. Bled the system. The temp gauge read cooler on the road but would fluctuate higher (to normal) when idling. It ran and idled poorly. This repair was made in the winter. Since it was the only repair I made to the vehicle at that time; I feel the issues experienced were direclty related to the non-stock t-stat. My gas mileage also suffered by ~0.5 MPG. I switched back to the stock t-stat within a week and had no further issues. Chevy... fun to say, not to drive. ;) Seriously, I liked my Blazer.
I am replacing the t-stat in my 635CSi, and they erroneously sent me the 75° t-stat. I was going to put it in until I saw this thread and remembered my past experience. I have ordered the 80° and will definitely not experiment again. Whew! I hate doing stuff twice.:)

[skr]

this thread is hilarious...
does a smaller water pump also help cooling?

...you shall never convince me a cooler t-stat makes an engine run hoter...

[Blitzkrieg Bob]

The weakest part of your car is the likely the radiator. It is a simple matter of physics when we tell you this: Energy is lost through heat. Transmissions, as they lose more and more heat, begin to cause more loss of power. However, that's only a small part - The worst part is the radiator! All sorts of heat is lost through the radiator - in essence - losing the horsepower through heat! Not anymore!! KaleCoAuto brings you the Radiator Insulatior - Simply slip over your radiator and enjoy the power! KaleCoAuto radiator insulation is made from only the finest asbestos, and is guaranteed to trap 90% more heat!

http://kalecoauto.com/index.php?main_page=product_info&cPath=1&products_id=35

[yaofeng]

Question: If you want your engine to run cooler. Forget about the harmful or beneficial effects to the engine. Do you select a thermostat which open at hotter temperature or cooler temperature?

According to your logic, you would select onw with a higher rating. Correct?

Question: When you are crusing at highway speed, would a cooler thermostat make the engine run cooler or hotter?

According to your physics. It would also make it run hotter. Correct?

[CarloE34]

I dont know who is rigth or wrong but here we always say to people who are driving a M20 or M30 lump to pull out the thermostat when they go to the mountens with a caravan.Best thing to do against overheating....???????
And now i here these storys i must say that i'm confused.For both storys there is something to say for.......

[Blitzkrieg Bob]

Id say it's a bypass system, and would be worse with out it.

[ryan roopnarine]

-a 180 degree thermostat doesn't mean you're going to run at 180 degrees (my favorite point)



normal operating temperature on an e34 is straight 12 o'clock, which corresponds to 182 dF
http://www.bmwe34.net/e34main/trouble/Data/gauge_overheat.jpg
the stock thermostat for e34s is 80 dC, which is 176 dF, which is pretty darn close.

[SnakeyesTx]

No, all this time I've been reiterating low speed traffic conditions, also known as real world conditions. Most of the time you're driving in them. When you're running on the highway up to speed, the passing air across the radiator generally is more than adequate to lower the coolant temperature given that all your hardware is up to par without restrictions or corrosion. In that instance the coolant most likely has ample airflow to dissipate the heat in a fairly short amount of time given at freeway speeds you have a 60-70 mile per hour wind going through it. But lets say you're hauling ass, then come to a fairly abrupt stop. Say you're tooling around 4k rpm for a good 8-10 minutes after your motor was brought up to operating temperature. I don't know you about you, but 9.9 times out of 10 the temperature jumps quite a bit as soon as you come to a stop since all the built up heat at a higher flow from the water pump turning rapidly all of a sudden has no where to go when you come back down to idle. That thermostat stays open for quite a long time to hopefully cool everything back down.

This whole thing was basically a no-brainer concept. The longer you hold the water in the radiator, the cooler it can get to cycle into the block. What's so difficult to understand about this? Where is it not absolutely CLEAR that when you lower the temperature the damn thing opens the LESS time the radiator has to do its job? What's the point of cycling coolant that doesn't get adequate time to cool?

Seriously ... now I'm just repeating myself. I've left more than adequate information about the matter. I've given more than enough sources, more than enough reasons, and more than enough logic to make even the least mechanically inclined people understand. I'm obviously wasting my time carrying this any further.

[ktteoh]

hmmm...it still seems a 50:50 split either way.

what i want to know is why is a reputable manufacturer like wahler producing a 75 degree version?

does anyone know what's the target market or application for the 75 degree model?

[Ross]

The thermostat regulates the flow by opening at the rated temp, the balance of the cooling system is responsible for the actual operating temp. All the stat can do is open or close. If the stat is wide open and insufficient cooling is available you will overheat regardless of what temp it opened at.
Snakeyes point is absolutely correct that coolant flowing too quickly through the rad. does not have time to transfer heat and in a marginal system can cause overheating.
If you have a properly operating cooling system you will not notice much change in operating temp with a cooler stat., your car will take longer to warm up though and will burn more fuel in the process. Engine wear is also greater due to extended warm-up.

[SnakeyesTx]

Older vehicles with carburetors that love to cruise along the highway I could understand benefitting from one. Since there isn't any computer controls or sensors, the issue of open and closed loop running isn't there, and air/fuel mixture would be controlled by you turning the screws. There would definitely be a market for such an instance.

[Blitzkrieg Bob]

applications for the 75 on older/other models

[Kakaire]

Ok guys, here is one form AFRICA. You all know it never snows most of Africa, but in a little in South Africa. My bima is a Japanese Import M20. By the way majority of aged cars here drive without thermostats atall.

There is a Forbia here that thermostats make cars overheat, to prove this ask anybody who leaves at the East African Port of entry (Mombasa). Other than new cars, every old car gets its thermostat removed in preparations for the 3000 km road journey back home.

Until I joined this board a year and half back now, I used to drive mine without a thermostat. I actually objected removing it while at the port of entry, hence car over heated midway of the journey back home when I stopped to gas her up. I removed it immediatetly.

My experience without a thermostat: car took longer to gain operating temp all mornings, it would ran needle in blue for like 35 km before needle is in 12oclock. Car would hold just fine in very heavy traffic with needle in 12oc. Car temp would drop while driving at night to 1/4. Car temp would also drop to 1/4 driving highway.

Right now I have 70d thermostat in, drilled, that operates fine at a needle below 12 oclock.

This is just my experience in Africa. as I write in my country (Uganda East Africa) 70% of vehicles here a second hand imports with majority from Japan and Europe, all with thermostats removed.

[shogun]

So what you say, even in Africa the thermostat is better.
In my opinion it depends on the design of the system.
And in a BMW it is clearly better to have the T-stat inside, because it
is a dual action T-stat.
If you remove the T-stat, most of the coolant will run the small cycle, that means it bypasses the radiator and just runs inside the engine.
The coolant goes the way of lowesr resistance.
http://s71.photobucket.com/albums/i155/shogun_bucket/?action=view&current=coolant_circuitV12.jpg&refPage=60&imgAnch=imgAnch68

[ktteoh]

shogun, i think your post has brought a better insight into my topic. could you elaborate on the 2 different modes of T-stat as designed by BMW - what you call small cycle and "big?" cycle coolant flow - i don't get that from your diagram.


So what you say, even in Africa the thermostat is better.
In my opinion it depends on the design of the system.
And in a BMW it is clearly better to have the T-stat inside, because it
is a dual action T-stat.
If you remove the T-stat, most of the coolant will run the small cycle, that means it bypasses the radiator and just runs inside the engine.
The coolant goes the way of lowesr resistance.
http://s71.photobucket.com/albums/i155/shogun_bucket/?action=view&current=coolant_circuitV12.jpg&refPage=60&imgAnch=imgAnch68

[shogun]

The engine in your car runs best at a fairly high temperature. When the engine is cold, components wear out faster, and the engine is less efficient and emits more pollution. So another important job of the cooling system is to allow the engine to heat up as quickly as possible, and then to keep the engine at a constant temperature.
And this does not happen without T-stat.

The T-stat's job is to block the flow of coolant to the radiator until the engine has warmed up. When the engine is cold, no coolant flows through the radiator. Once the engine reaches its operating temperature, the thermostat opens. By letting the engine warm up as quickly as possible, the thermostat reduces engine wear, deposits and emissions.

The small cyle is within the engine only, large cycle means including radiator and heating system.

In my opinion it does not matter which T-stat you select, get the one which is best for the engine to work at it's designed temperature as soon as possible.
When it has reached the temperature the T-stat opens, and every T-stat opens then, no matter if it is designed for 70,80 or 90 degree Celsius. Open is open. And then the coolant runs thru the radiator.

(75 vs 88 Celsius): if I would live in a cold country, I would choose 75 degrees, because then my heater would heat earlier.

[ktteoh]

shogun, thank you for your informative reply. i actually have what i believe is a 88 T-stat. my mechanic asked me if i want to try a 75 T-stat just to lower the heat stress in the engine bay - here being the hot & humid tropics.

btw do you have a picture to show where hole should be drilled on a T-stat to enable better bleeding - i need to show this to my mechanic.

[shogun]

BillR says he has never needed it to bleed
http://www.bimmer.info/forum/showthread.php?t=25046&highlight=hole+thermostat
Here you can see a hole
http://www.bimmer.info/forum/showthread.php?t=24322&highlight=hole+thermostat
Gale:
http://www.bimmer.info/forum/showthread.php?t=23613&highlight=t-stat+hole
see at bottom
http://www.bmwe34.net/e34main/maintenance/engine/Coolant%20replacement.htm

75 vs 88 Celsius): if I would live in a cold country, I would choose 75 degrees, because then my heater would heat earlier.

[tnt525i]

heres my experience,
i live in the caribbean and i installed the 75 degree stat in my car (because the 88 degree stuck closed and i had a choice of 75 or 88) since then in traffic the needle is exactly on the line in the center of the gauge, when driving on the highway. the needle is a tick to the left of center representing the engine is running cooler, so wether this is good or bad i dont know, because the average temp here in trinidad is 30 deg. celcius. i thought i'd go for the lower temp stat to compensate for the hot climate here, just my 2cents