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Hi All.
Looks like it is the season for a number of stuck thermostats, so in hopes of helping others new to the subject I'll just share my experience from my thanksgiving drive to see the family...
(experts can skip this, I'm just writing this for some of the new-to-DIYers here since I am seeing a lot of these questions coming up lately).
Troubleshooting:
On this long highway drive I noticed my temp go down in the blue and no heat inside the car (1996 2.3L 900s) I recently replaced the temperature sending unit and so I doubted it was that, but just to make sure I pulled over and felt the engine was cold to convince myself that the temp sender was telling the truth (it was). That only left the thermostat being stuck open (coolant flowing all the time, hence the cold temperature of the motor, coolant, and consequantly cabin heater). This of course is made cooler still by driving at high speed (highway for 5 hours) since the cold air was rushing in and around the motor faster. That's how you diagnose that. No danger of running cold, just bad gas milage. If your stat is stuck closed however, you will overheat and burn up your head gasket etc. so do not drive in that case.
In my case however, I made it home no problem (lucky we have seat heaters, cause there was no other heat in the car! :)
R&R:
There are excellent instructions and photos provided by Mattias here:
http://bellsouthpwp.net/m/a/mattiaso/WebPages/Auto/therm.htm
Correx:
But I have a couple things to add. On a 2.3L 900s I can tell you that the thermostat DEFINITELY uses 12mm bolts not 13 as it says on that page (I don't know if other people have 13mm bolts, but make sure you are using the right socket because you don't want to strip these).
The bracket bolts are 10mm as stated.
Draining:
I have read the various techniques for detaching one hose at a time, and syphoning and using a syringe to get a little coolant out at a time, and not spill any. Dean describes this elsewhere, read the various techniques and pick what makes sense to you. I have my own way which I have used without spilling but a few drops and that is worth the ease for me (one hose clamp and 2 minutes work), but to each his own. Whatever works for you and doesn't kill cats is good. (btw, my method is to use a custom funnel that I made from a large milk jug and cut it around to fit nicely around the bottom rad hose and have a tube on the small end of the funnel to direct the coolant away, then I quickly remove the bottom hose with the funnel in place and it all goes draining out the custom funnel except for the first bit of seeping before before the hose comes off (a couple drops). The cost of my nutty-professor funnel is about $0.00 and I've used it for years.
The other thing on mattias' site is he says he wasn't sure whether to use 82C or 89C thermostat. I think turbos are spec'ed for 82C, but I'm not sure. Mine (natural 2.3L) was originally a 89C stat and I have stuck with that (they are ususaly stamped in the stat somewhere). Sure enough the old one was stuck open. I threw both (without gaskets) in a pot of boiling water and you could see the new one open and the old one did nothing but stick open. Took them out of the hot water and the new one closed up nicely. The old one still stayed open. Put a new gasket on.
Flushing & Refilling:
I ran water through the rad (via a hose in the filler tank) and engine (via hose in the thermostat 'hole') to flush. Refit hoses and thermostat and termostat cover.
IMPORTANT (this isn't mentione in mattias' instructions, but is assumed): when you bolt back the aluminum cover don't torque one bolt all the way down then the other, you can crack the soft housing with the bolts. Do a little on one then the other till you can see a good seal devlop, keeping the pressure even, but don't overdo it (you can always tigthen a little more if you see a leak there afterwareds).
Refilled with 1 Gal. Zerex G05 (aka Mercedes coolant), and the rest with distilled water. The only problem was to find the right torque on the clamp on the bottom rad hose which connects to a plastic outlet and you don't want to overtighten that, but I was getting a seeping drip there once the pump came on. I just put on a new stainless hose clamp beside the factory one (there is room for two) and found that two moderately tight ones stopped it without having to clamp down hard on either of them.
Just my experience:
Just putting it out there in case it helps others. If I couldn't find a contact on Mattias's site I would have sent him the note about the 89C stat and the correct 12mm housing bolts.
TomL
posted by 24.21.199...
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