Replaced original Tstat and have same result as others - Page 2 - PeachParts Mercedes-Benz Forum

jt20 · #16 10-26-2008, 04:03 PM

FSM says the system is self purging/ bleeding.

"The thermostat housing has an automatic venting
system."

EricSP · #17 10-26-2008, 06:29 PM

I will try to unscrew the cap and put it on the first detent.

jt20 · #18 10-26-2008, 08:20 PM

I am running cool since tearing the engine open, it is effecting efficiency. I used what I thought to be a nice looking t-stat. It was a Behr, 87*, and may have been from a 240d.

I thought normal t-stat failure resulted in overheating, not underheating.

for reference: the coils face the block.. correct?

#19 10-26-2008, 08:24 PM

Quote:

Originally Posted by jt20

I thought normal t-stat failure resulted in overheating, not underheating.

No, it can fail in the open or closed position.

Quote:

for reference: the coils face the block.. correct?

Yes.

nhdoc · #20 10-27-2008, 06:41 AM

Quote:

Originally Posted by jt20

FSM says the system is self purging/ bleeding.

"The thermostat housing has an automatic venting
system."

There is a small hole in the edge of the T-Stat with a little rivet looking valve in it. That is part of the venting/bypass system and there is an arrow on the body which is supposed to be pointing up when the t-stat is installed (assuming it is vertically oriented). Some aftermarket t-stats don't have the hole and sometimes people don't install them facing up which can have an effect on the self-purging system.

Phil · #21 10-27-2008, 10:03 AM

Quote:

Originally Posted by Brian Carlton

When you replaced the thermostat, did you remove the upper radiator hose and completely fill the head with coolant?

This is one of the things a lot of people miss but makes the biggest difference. I never change the stat on any car with out doing this. The stat will not open until it senses hot water and if you do not have water in the head for it to sense it will never open. Also as others have stated you must install the stat with the bleed hole on top.
One question; do you know what temperature rating the new stat is?

jt20 · #22 10-27-2008, 11:20 AM

80*c

mespe · #23 10-27-2008, 12:24 PM

Quote:

Originally Posted by Brian Carlton

When you replaced the thermostat, did you remove the upper radiator hose and completely fill the head with coolant?

I know you might cringe, but I squeeze the top radiator hose, then plug the little line going to the top of the expansion tank and then release the upper hose, and repeat. this usually sucks in a bit of antifreeze from the expansion tank.

Phil · #24 10-27-2008, 02:17 PM

Quote:

Originally Posted by mespe

I know you might gringe, but I squeeze the top radiator hose, then plug the little line going to the top of the expansion tank and then release the upper hose, and repeat. this usually sucks in a bit of antifreeze from the expansion tank.

Interesting idea, I'll have to try that some day.

Jim Condax · #25 10-28-2008, 05:52 PM

Quote:

Originally Posted by nhdoc

You also ought to run it unpressurized for a couple of days (cap set at first detent) so any air bubbles can purge themselves. If you fill it and run it with the cap closed it can become airbound because the bubbles expand when heated and can't move.

Thanks for the tip. I had the same problem. After changing t-stat, waterpump, flushing radiator and refilling with G-05, temp gauge was at 100 C. Loosened cap on coolant reservoir to first detent and drove for ten minutes. Must have been trapped air. Gauge now reads between 80 and 90. Easiest fix yet.

Thanks again.

nhdoc · #26 10-28-2008, 06:19 PM

Quote:

Originally Posted by Jim Condax

Thanks for the tip. I had the same problem. After changing t-stat, waterpump, flushing radiator and refilling with G-05, temp gauge was at 100 C. Loosened cap on coolant reservoir to first detent and drove for ten minutes. Must have been trapped air. Gauge now reads between 80 and 90. Easiest fix yet.

Thanks again.

Glad to have been of assistance.