M20 UNDERheating?

[packratbimmer]

I have found that the Wahler 88 degree stat behaves closer to the 80 degree spec. The B/T (Behr-Thomson) 80 degree performs better to factory specs in my experience. I run the Wahler 88 in the winter in Maine so the car heats up a bit faster and stays at the 12 o'clock mark.

[CorvallisBMW]

I pulled out the old thermostat and verified it and the Wahler one opens way too early, like around 60°C, whereas my old Vernet one opens around 80°C like it should

Glad you found the culprit.

[JinormusJ]

It's your t- stat. Change it back, and I'll bet you're good to go

Changed it back to my old one just this morning: heating at 7/16ths, like it should. I'm a happy guy; it only took two extra jugs of BMW coolant though LOL
But I managed to save and filter most of it, so I have 3 jugs of 50/50 on tap now

I seem to have the best luck with Vernet though; out of my eight or so timing belt changes, that one was never let me down. This is the only one I've ever had problems with, and it was the more expensive Wahler one. Go figure

If it ain't broke, don't fix it: certainly applies here

It's not uncommon for brand new t-stats to be defective, no matter the manufacturer. Best to test+verify.

I pulled out the old thermostat and verified it and the Wahler one opens way too early, like around 60°C, whereas my old Vernet one opens around 80°C like it should

Called up the shop I bought it from and they said the best they can do is a warrantee exchange even though I don't need a Thermo anymore... Whatevs

[CorvallisBMW]

It's not uncommon for brand new t-stats to be defective, no matter the manufacturer. Best to test+verify.

[TobyB]

It's your t- stat. Change it back, and I'll bet you're good to go.

And oddly, I've had them change behavior when they dried out. They SHOULDN'T,
but especially on older ones, they don't seem to like getting dry. Rubber seals?

And yes, I've had trouble with Wahlers, Vernets, Stants, and genero- zone ones, too.
The wax inside is a pretty cool trick- and apparently, not trivial to get right...

hth

t

[JinormusJ]

You can test your t-stat but placing it in a pot and heating it on the stove. Use a thermometer to verify the temp that it opens at.

I did this with my old one and after comparing pictures and seeing it open at 80°C myself, I found that it's the Thermostat I always usually use made by Vernet.

My old one seems to be working fine.. Except; only the center spring moved when it openned. Are both springs/flaps supposed to move or is the smaller spring pressure activated versus temp activated?

At this point, I'm thinking of taking the new Wahler out and putting this Vernet one back in

[roznic]

Same thing with mine, heats up to about 62-65 according to the pic. Interesting fact, that I just did s52 swap and temp gauge does same thing as with good ol m20?!

[JinormusJ]

Truth. Those gauges aren't worth a damn as far as measuring. They just show relative temperature on your specific car (basically if it goes to the same spot it always does, good. If not, check it out)

Day before timing belt: heats to 7/16ths
Day after timing belt: heats to 1/4th

Therefore, "if it goes to the spot it always does, good, if not, check it out". So.. Then.. I digress

Don't think that gauge is accurate. Mine once sat at the "106" Celsius position for whatever reason according the picture you posted, and Tuner Studio was saying 210* Fahrenheit, which is 98* Celsius.

I never claimed these gauges were accurate, I'm posting this thread because my car is doing something it was never doing before: eg under heating to 1/4th versus heating normally to 7/16ths (which is what my car used to heat at)

Here, 60/40 is worthwhile in the summer time because it gets hot (a couple years ago we have 63 straight days over 100 degrees) from April to September. But if it's not consistently how 60/40 makes no sense unless you track the car a bunch. Unless your running hot already, changing 60/40 is pointless.

And I was thinking of that instance while reading this too, laughing to myself.

I thought of trying a different mixture because during summer here it gets consistently 100+ and on freeway days I would consistently "over"heat to 9/16ths on my gauge; whether or not that's attributed to the fan clutch; probably, but I thought having a slightly more water-biased mixture on top of replacing the clutch would be good but didn't think it would effect normal operating temperatures this much

Either way, I was close, but no cigar on adding the 50/50 mix; still heats to 1/4th when the norm for this m20 should be 7/16ths

[crappycoco]

Mine does the exact same thing since i got it. I have 50/50 pre-mixed prestone coolant in there and thats it. While driving through death valley and/or autocrossing, it can get close to 12'o'clock or a hair over it.

[DaveSmed]

Don't think that gauge is accurate. Mine once sat at the "106" Celsius position for whatever reason according the picture you posted, and Tuner Studio was saying 210* Fahrenheit, which is 98* Celsius.

Truth. Those gauges aren't worth a damn as far as measuring. They just show relative temperature on your specific car (basically if it goes to the same spot it always does, good. If not, check it out)

They also vary signifigantly car to car. There are something like 15-18 total connections in that circuit, (around 5 dedicated) and that coupled with 25 some odd years leads to a bit of variation.

[HennaE30]

You know, you were the exact person I was thinking about when I typed this up. The whole time I was thinking.. Man, remember when I was wrong about coolant and I told Henna?

Gonna run and get myself another jug of BMW coolant and refresh the system. Hopefully that solves it

Here, 60/40 is worthwhile in the summer time because it gets hot (a couple years ago we have 63 straight days over 100 degrees) from April to September. But if it's not consistently how 60/40 makes no sense unless you track the car a bunch. Unless your running hot already, changing 60/40 is pointless.

And I was thinking of that instance while reading this too, laughing to myself.

[CorvallisBMW]

You can test your t-stat but placing it in a pot and heating it on the stove. Use a thermometer to verify the temp that it opens at.

[ak-]

Don't think that gauge is accurate. Mine once sat at the "106" Celsius position for whatever reason according the picture you posted, and Tuner Studio was saying 210* Fahrenheit, which is 98* Celsius.

[JinormusJ]

Yes. It will. The more water you run in your car, the longer it'll take to get warm, as well as possibly running cooler. Water displaces heat better than ethylene glycol (most coolants) causing it to run cooler.

You know, you were the exact person I was thinking about when I typed this up. The whole time I was thinking.. Man, remember when I was wrong about coolant and I told Henna?

Gonna run and get myself another jug of BMW coolant and refresh the system. Hopefully that solves it

[HennaE30]

Go where from there.. Exactly..?

If it makes any difference, I checked this morning with a traditional food thermometer at the coolant temp sensor hole and it read 150°F (65°C)


Could my coolant minute have anything to do with it? I used to do 50/50 blends BMW OEM coolant, but this change I switched to 60/40 water/coolant BMW OEM mix

Yes. It will. The more water you run in your car, the longer it'll take to get warm, as well as possibly running cooler. Water displaces heat better than ethylene glycol (most coolants) causing it to run cooler.