Thermostat Madness

[mikepellegrini]

Okay, so I'm doing my proactive maintenance, getting my car ready for the summer. The thermostat was stuck open.

So I removed the waterpump and got the old thermostat out - it was broken. Cool.

My pump is an updated old-style pump with the 4.5mm ledge, so I ordered a new Wahler 80C thermostat - 944-106-129-05-M2 (per Clark's). I got it a few days ago and it looked pretty much the same as the old one - it was hard to tell the precise dimensions because the old one was kinda twisted.

I installed the new thermostat with the old (thin) o-ring (which was in great shape). The snap ring fit very snugly. Perfect.

I slapped it all back together and voila - the thermostat didn't open. I had a cold radiator, a cold bottom radiator hose, hot top hose and great heat in the cabin - all bled out nicely.

I pulled it apart (with the pump still on the car, this time). The first time I boiled the new Wahler thermostat, it seemed to open late - around boiling. So thinking the thermostat was defective, I went and got a new Beck-Arnley one - and boiled both.

This time, the old new one (the 80C Wahler) opened on time.

Thinking maybe I'd screwed up the waterpump gasket and blocked something important off, I put it back together and filled it with plain water - without any thermostat - and it cools just fine. No obstructions.

All which has me wondering if I got the right thermostat in the first place. Here's my collection:



Far right is the old one; middle is the newest one (as yet untried); at left is the one that wouldn't open when it was installed.

The dimensions are all the same except for the outlet on the Beck-Arnley is smaller. I don't know how far the bottom block-off travels on either but the overall distance on both look the same when full open.

Have I got the right thermostat for a pump with a 4.5mm ledge? The part number (944-106-129-05-M2) on the box was correct, but there is no number on the thermostat itself.

[Rasta Monsta]

The far right pic is reason enough never to use that stat, IMO.

[mikepellegrini]

Yeah, you're probably right. The weld (or whatever it is) just broke. Not exactly an advertisement for Wahler.

Got any experience witht he Beck-Arnley?

[Rasta Monsta]

I don't, but I have heard a few times that non-OEM stats will stick just as you described. . .not that helpful here, however, because according to Pelican, Wahler is the OEM supplier!

[mikepellegrini]

Yeah. So much for the OEM supplier.

Oh well. I guess I'll bite the bullet and put in the Beck-Arnley one tomorrow. At the worst, since I discovered how to get the snap ring out (I made a pick-kinda tool that works great), even if it doesn't work I can get it out pretty quick (knock on wood).

I looked at my spare 951 engine - it has the same 80C Wahler thermostat as I have (that failed).

That car has a 7mm ledge in the waterpump, but whoever installed the thermostat didn't put in the spacer and the thermostat was rattling around.

Oh well...

Apparently, the thermostats for both the 4.5mm and 7mm ledge are the same - it's just in the 7mm, you insert the spacer?

[Techno Duck]

Went through this a few days ago on my 951. I put in a new Laso waterpump and used the 80*C Laso branded thermostat provided. Car ran noticably warmer, never overheated but easily 15-20 degrees warmer during all conditions. This is going off the digital gauge i have running off the upper radiator hose.

The other day i was fixing some boost leaks and had the car idling in my buddies driveway, after a few minutes coolant puked out from the overflow tube on the expansion tank. I had the coolant over filled a fair amount, but the coolant temp was around 220 degrees which i have only seen sitting in NYC traffic in the dead of summer on occasion.

Took the old thermostat out and boiled it and the Wahler replacement i got. Both are set for 80*C and were in a rolling boil for a few minutes. I took them both out at the same time, you can see the Laso stat is not open nearly as far as the Wahler.



With the new Wahler stat in the car is back to normal in terms of coolant temps. What a pain in the ass for a $14 part. I am very happy i installed the LR radiator drain kit. Makes draining the coolant mess free and also makes it easy to reuse. This has saved me a few times after i had to fix a few leaks (silicone hoses needed some 'break in') after my rebuild.. and again after i did this thermostat. Nothing brightens my day like removing the lower radiator hose and having 2 gallons of coolant pour all over the place.

There are two different seals used for the waterpump, a thick and thin one to put it simply. With the thick seal fitted there was no space for the snap ring. I used a thin seal and two of the shims which was perfect. With 1 shim the thermostat could still be spun by hand.

[mikepellegrini]

Yeah. That's the same sort of potential problem I was wondering about with the Beck-Arnley I bought.

With a smaller (26mm) opening as compared to the 31mm opening on the Wahler, you wouldn't think it could move as much water - even though it does open as far.

Gah! I have a known good 80C Wahler off my spare engine...

[mikepellegrini]

I put it back together today using the known good 80C Wahler from my spare engine and it cools great.

What a PITA, that the first new thermostat was defective (it came from Pelican).

But on the brighter side, I'm much more practised at changing thermostats, now...