hole in the thermostat question

[BigKriss]

I put a hole in the thermostat and placed the thermostat at 12 o'clock to help bleeding on the cooling system. Now the car runs between 1/3 and 1/2 way in the temperature range. I'm wondering if running at 1/3 operating temperature is okay?

The hole was 9/64" ~ 3.5mm in size.

I have a spare theromstat ready also.

[Rick L]

You should not put a hole in thermostat. Definitely NOT a good idea. It might take longer to reach operating temperature. As everyone knows, cold engine is just as bad as hot engine. If you look at the thermostat, there is an arrow. That arrow supposed to be either UP or DOWN. By putting in the thermostat correctly help bleeding the air from coolant.


I put a hole in the thermostat and placed the thermostat at 12 o'clock to help bleeding on the cooling system. Now the car runs between 1/3 and 1/2 way in the temperature range. I'm wondering if running at 1/3 operating temperature is okay?

The hole was 9/64" ~ 3.5mm in size.

I have a spare theromstat ready also.

[BigKriss]

okay thanks for your comments Rick.

[Tiger]

It will never reach operating temperature and burn more gas. Always a bad idea to drill a hole... if any, would be the smallest hole possible.

[BigKriss]

okay, thanks tiger

[Dave M]

3.5mm is a pretty big hole. I used the smallest bit I had (1+mm?) and the M50 runs just a hair left of center. It (drilling a hole) seemed to all the rage a few years ago, but its definitely possible to bleed these cars without.

Dave

[ss2115]

Hi BigKriss.

Nothing wrong with a very small hole in the themostat, but 3.5 is way too big.
Less than a 1mm used to be standard in most off the shelf thermostats.
Its for a bleed and also to allow just a small amount of water circulation so that water was moving around the engine and radiator and past the coolant sender.

At the very small size it made no difference to warm-up time or hot running. 3.5mm will certainly slow the warm-up time from a cold engine.

I'm not sure that it should have made a huge difference to the running temperature but obviously it has. Must be a very well sized radiator and cooling volume to find a 3.5mm passage over-riding the thermostats opening.

But as already stated, running too cool is detrimental as is running too hot. If the clearances haven't been taken up by expanding metals, you can burn more oil, have less performance, and the ECU may keep the mixture a bit richer than it should be as well (ie: increased fuel consumption). Engine wear will increase as some clearances meant to open won't, and the oil will be thicker and a bit more sluggish to pump around.
ie: Don't pull any 6 grand acceleration runs in this condition.

[whiskychaser]

I'm going to disagree. OK I've got an M50 not an M30 but my experience is quite different. When my stat was stuck wide open it would take 15 minutes for the car to reach full temp. With a new stat it took 10. I'm taking into consideration the fact yours might have the 'tropical' cooling pack. Mine has it too. I wouldnt drill a hole in a stat but its made my day you used a 9/64 drill. I've still got BSW spanners and sockets in the toolbox:D The question is how long does it take to warm up fully? Or does it?

[BigKriss]

Thanks for everyones comments. I will change the thermostat today. It took about the same time to warm up from dead cold then with a "normal" thermostat.

I did notice though the coolanty system was a lot easier to bleed than normal.

[632 Regal]

2mm MAX 1 or 1.5 is more ideal to help bleed the system. 3.5 is way too big and will mess up operation of heating it up and controlling the temperature. The BMW stats that I bought have a small orfice and a checkball to control direction of flow for whatever reason.

[gale]

I've been driilling a 1/8" hole in every m20, m30, and m50 thermostat I've changed in the last 15 years and have never noticed any difference in the time it takes the temp gauge to hit straitgh up 12:00 o'clock. The hole is small in comparison to a fully opened thermostat and greatly speeds up the bleeding process to the point that it's almost self-bleeding. Just did another m20 last night that I swapped heater cores & all new hoses & drained the block & it filled & bled fully the 1st time, needing one token cracking of the vent screw & quickly warmed up to 12:00 o'clock & not any further.

[BigKriss]

Yeah, I took the car for a spin last night, with a new unmolested termostat, 71 degree cecluis temp item. Driving the car over 30 minutes it still stayed between 1/3 and 1/2 operating temperature. weird.

I dont think its in backwards, because it wont seal properly, if the termostat is in backwards.

[gale]

Yeah, I took the car for a spin last night, with a new unmolested termostat, 71 degree cecluis temp item. Driving the car over 30 minutes it still stayed between 1/3 and 1/2 operating temperature. weird.

I dont think its in backwards, because it wont seal properly, if the termostat is in backwards.

Normal needle position is straight up 12:00 o'clock with an 80c t-stat. I would expect a 71c t-stat to run on the cool side.

[BigKriss]

How much cooler though? Another run I went for last time never got over 1/3 of the temperature range. Somehting is not right here.


Normal needle position is straight up 12:00 o'clock with an 80c t-stat. I would expect a 71c t-stat to run on the cool side.

[Ross]

The 3.5 mm hole isn't the issue. A properly operating t-stat should be able to manage flow and regulate temp. I'd run a warmer stat. Why 71*c?

[Ross]

How much cooler though? Another run I went for last time never got over 1/3 of the temperature range. Somehting is not right here.
9*c, your gauge is indicating this

[whiskychaser]

. Somehting is not right here.

I agree. I dont think a hole in the stat or the 71 or 80 degree opening time is the issue: once its open its open. And after half an hour whichever one you use should be wide open. My concern would be if it gets too hot you wont see it. I have a couple of gauges to set up radiators but your local garage will have something like this thats a lot more accurate:
http://www.tooltopia.com/mastercool-52225b.aspx?utm_source=pricegrabber&utm_medium=cse&utm_term=MAS52225B&utm_campaign=pricegrabber_r1
Worth a drink for a mechanic friend?

[BigKriss]

Thanks for everyones comments. I bought the cooler thermostats becasue I didn't know any better. I just get a part number from realoem.com and give it to a part supplier. I have two theromstats, one is 74 degree with no hole and a 71 temp item.

The weird thhing is also, I'm unsure if I bled it properly. I'm unsure becasue I always thought that if if was bled propelry it wouldn't overheat and it hasn't but when I was bleeding the coolany system, I never stopped when there was just water coming from the theromosta housing, when there was sair stilling coming out (occassionaly) I closed the bleed valve and took the car for a run.

[BigKriss]

Yeah, I put the 75 degree thermostat back in the one with the hole and it seems to be working alright again. So I hope I don't have to muck around with it anymore. fingers crossed.

I also need a new radiator drain plug. Somehow the o-ring broke on it :(

So does anyone know what other o-ring I can use for it? The plug is still in good condition.

The engine seems to be running okay.

[Dave M]

Congratulations. You've taught a few of us a thing or two in your struggle for an errect needle ;)

Not sure if you're near a dealer, but the drain plug should be available there for a few $$ (at least dealers here carry them). If not, then you should be able to find a suitable replacement. Just bring the plug to your local auto/hardware/fastner store and test fit until you find the right $0.10 o-ring.

Dave

[BigKriss]

Yeah, I spoke to soon, the 75 degree theromstat with hole is still running cold. On the other hand for the drain plug o-ring, I used a fuel injector o-ring, its almost the same diameter, its a lot thicker though. It works without leaks.