yet another overheating thread

[Randell]

sorry for starting another one of these, but i've looked through a ton of overheating posts, most of which were solved with bleeding... but im not sure if im bleeding right, is the coolant supposed to flow out rapidly when opening the screw?

i opened mine and it did nothing for a couple of seconds (no air hissing or anything) and then coolant began slowly trickling out... i didn't loosen the screw much though, just enough to make sure it was fluid and not air or bubbles

the problem: the temp needle is sitting fine on halfway until about 3-5 mins into my journey, where it'll gradually creep up until it hits just below the 3/4 mark (haven't kept driving after that, luckily)... i let it idle in the garage and it climed to basically the 3/4 line, where i switched it off

no air coming out, radiator is hot, the fan is blowing (but it does seem a little bit slow)... there's a slight squeek from the fan belt but if it's slipping it's not considerabe.. this sound could also be from the water pump though.. coolant level is good

the temp started acting up less than week ago, at first it was just in traffic, now it seems to happen when driving too, and just getting worse at idle

thanks for reading, any ideas will be appreciated

[Javier]

Bruno's page overheating tips (http://www.bmwe34.net/e34main/trouble/overheating.htm)

from it, I learnt about the Winfred's "Pisser", a tiny hose running from the top left of radiator to the expansion tank. If clogged, car will overheat. I did unplug and blow mine, immediately found that there was some dirt acting as a check valve. I did not over drill the hole as suggested on the link, but cleaned the hose and every thing has gone fine since.

Additional to that, remember the basics of the operation of the cooling system. There are two coolant circuits, one is a short circuit that circulates the coolant in the engine until it is warm (about 85 degrees C), once warmed, the tstat opens and activates the long circuit that circulates the coolant trough the engine and the radiator. If tstat does not open, the car will overheat (tstat is a temperature regulator controlling the amount of coolant going trough the radiator). Not opening the tstat is caused by stuck/broken/faulty tstat, or air in tstat housing. Bleeding is hard wile engine is cool if you do not have the hole in the top of tstat base, if tsat is original, it won't have it. If engine is hot and you do not get bleeding pressure, be sure to turn on cabin heating to provide alternate paths wile tstat is closed.

Also check opening/closing of tstat by checking radiator big hoses temperature. If tstat is opened, the lower one should be hot, the upper very hot, also you should feel left side of radiator hot, and if gauge shows overheating, auxiliary fan should turn on. Hot engine and cool radiator is a clear symptom of closed tstat.

Javier

[winfred]

that about covers it

[Mitch90535im]

Bruno's page overheating tips (http://www.bmwe34.net/e34main/trouble/overheating.htm)

from it, I learnt about the Winfred's "Pisser", a tiny hose running from the top left of radiator to the expansion tank. If clogged, car will overheat. I did unplug and blow mine, immediately found that there was some dirt acting as a check valve. I did not over drill the hole as suggested on the link, but cleaned the hose and every thing has gone fine since.


Javier

Ditto for me. Mine started happening shortly after I had flushed and filled with new coolant, so I had myself (and everyone else on this board) convinced that it was a bleeding issue, then I believe it was Winfred who suggested the pisser line. This was after I had replaced the fan clutch, thermostat, and was preparing to replace the water pump, and also after bleeding and topping 15-20 times. Came home at lunch after reading the suggestion, took the line off at the radiator and blew through it, bingo! Problem solved.

[Kalevera]

True. Check the pisser. I recently saw a 535 where RTV (!) had been used to seal the housing/cover flange during a tstat replacement. It wasn't long before little pieces of RTV made it up to the bottleneck at the expansion tank and clogged the heck out of it.

best, whit

[uscharalph]

Is there a pisser line on cars with radiators thath have expansion tanks?

[Javier]

Javier

[Kalevera]

All engines cooled with the conventional antifreeze/distilled water mixture employ the use of an expansion tank. M20 and M50 E34s have the tank built into the left side of the radiator; M30 and M60 E34s mount the tank on the firewall directly in front of the blower motor. The latter have an intermediary ("pisser") line between the radiator and the tank.



best, whit

[Randell]

thanks for the replies everyone

i checked the temp of the hoses, the lower one is quite warm and the upper ones are hot, so that seems to be ok... there are no cold spots on the radiator, and there seems to be coolant pressure (when i release the expansion tank cap it hisses)... so I assume the tstat is functioning correctly.. there's definately no air in there either, i bled it a few times with the heater on full and got nothing but fluid...

i drove into work this morning and the temp remained normal for longer, but after about 12 mins it started creeping up again, and was just before the 3/4 mark when i got to the office... i'll check that pisser line as soon as i get home, thanks for the tip!

[SRR2]

How, exactly, does this pisser line work -- what is its purpose? I mean, how does something this small, if plugged, cause the engine to overheat?

[winfred]

it allows the air bubbles that form in the system to bleed out of the radiator, if left to build up long enough the thermostat will get air locked and not open (not get heated by the coolent due to insulating air pocket)


How, exactly, does this pisser line work -- what is its purpose? I mean, how does something this small, if plugged, cause the engine to overheat?

[Randell]

well i just took the pisser line off at both ends, blew a lot of crap out and emptied about 1 litre of pretty murky coolant, but the heat still climed up... it doesn't seem to go past 3/4, but when i pull up and open the hood i can hear the coolant getting ready to boil... not good

bled it at 3/4 and got nothing but coolant, no air, no bubbles... the aircon works so the aux fan is obviously spinning, and if i turn the heater on the temp does go down about 1.5 needleheads, but it's still halfway between 1/2 and 3/4!

[Kalevera]

Hmmm...sounds like the tstat isn't opening, the radiator is partially clogged, or the water pump is starting to go south. Actually, since there's a squeak in the belt, check the water pump bearings for play and visually inspect to see if it's got cooked coolant around them. I'll still suspect the tstat: pull the cover and remove it from the housing, button everything back up and go for a quick drive on an open road where you can go a consistent 80 or 90 kmh. Don't run the A/C when doing this. Watch to see if the temp gauge drops. After less than 5 minutes of traveling under way, it should be down to the 1/4 mark -- don't let it go down any further. By stopping and idling for a bit, it should return to the 1/2 mark or start overheating. This will confirm that the radiator and water pump are working as they should be.

Alternatively, you could stick the tstat in a pot of water and bring it up to something close to boiling temps. The tstat should be fully open at 80 degrees, less if you have a warm climate tstat; don't let it sit in boiling water.

When was the last time the car had a coolant flush?

best, whit

[winfred]

with the cap off do you see coolent squirting into the bottle during a rev of the motor from the pisser line?


well i just took the pisser line off at both ends, blew a lot of crap out and emptied about 1 litre of pretty murky coolant,

[Randell]

hmm i always though coolant would go everywhere if i started the car with the cap off!

there is definately coolant coming back to the resoviour, i was going to take the thermostat off tonight but someone at work said i'd need a new gasket before i put it back on, and then i called my mechanic and he told me not to try the car without the thermostat in, which it what i was planning to do

so... im just gonna take it in tomrrow morning. the amount of oil residue in the coolant from the strange episode i had about 8 months ago necessitates a cooling system flush anyway, which i wouldn't be able to do

thanks for your help guys!

[Javier]

well i just took the pisser line off at both ends, blew a lot of crap out and emptied about 1 litre of pretty murky coolant

did you verify that plastic tubing at both ends of the pisser are clean?


the aircon works so the aux fan is obviously spinning, and if i turn the heater on the temp does go down about 1.5 needleheads, but it's still halfway between 1/2 and 3/4

Did you actually see it spinning (trough the grille) wile the gauge temp is high? I have no doubt A/C turn it on, what about temperature switch in radiator?

Javier

[Javier]

as in BMW vehicles, contrary to USA vehicles, tstat is a commuter switch, I mean, it opens one path wile closing the other, so the cooling system will not work as intended to.

You can check tstat as Lowell suggested, boiling water, a cooking thermometer, you can see it opening and at what temperature, do not overheat it as it may get damaged. (as long as there is still some water you won't reach beyond 100 degrees C.

the amount of oil residue in the coolant from the strange episode i had about 8 months ago

Sorry don't remember this, but sounds very bad to me

Javier

[JonE]

Are you sure your viscous fan clutch is blowing air around vigorously? I mean, like Jeff usually asks, does it sound like a big truck taking off from a standstill, especially when the engine is heated up? If that fan clutch is not blowing alot of air, then it could be toast. Just something else to check and fairly easy to check. When heated up, that fan should come to an abrupt stop when engine is shut off, it shouldn't be "free wheeling". When working properly it really helps cool the radiator fluid.

[Randell]

just got a call from the shop, they replaced the thermostat, flushed the old crap out and filled it with blue bmw coolant and apparently it's running fine now

thanks to everyone for putting in ideas, i know a lot more about the cooling system than i used to... would've been nice if i'd done the fix as well, maybe next time ;)