replace that t-stat!
 

rick, you have exactly the same symptoms i had - replaced t-stat with a bosch. no problem ever since. the temp should show around 80-85 deg c. even as it was 15deg f out this morning the gauge showed 80 deg c after about 15 mins. of driving. replacing the t-stat will make a world of difference to the amount of heat you get.

Rick,

A stuck-open t-stat will make the engine take longer to warm up, when ambient temps are fairly high. When it's cold out though, it will never let the engine reach operating temps. You almost definitely have a bad t-stat, replace it and your heater should work again. You didn't notice this in the summer because it just took longer to warm up, but did reach normal temps eventually...

:)

Well I guess that settles that, I'll replace the T-stat.. Now, when I went to change the thermostat of SD The head of one of the bolts broken clean off (galvanic corrosion). Is there any tricks to getting these bolts out without break them?

Yes there is a trick to getting the bolts out without breaking them!

hit them with a hammer firmly before attempting to break them loose. Naturally, if the cad plating is gone... new bolts.


??? So this jumping gauge question. Mine has good fuses(not so old) and the temp connection on the head is clean. It seems like the gauge jumps occasionally between 85-95 and then back down. I'm not sure how a linear resistance element could behave this way ?????? Is the sensor bad -$10 is cheap but I like to diagnois my problems and not throw money at them=)



Michael

The Haynes manual for the 123 series states that the thermostat for these cars should be fully open at about 94C. My car's operating temp is 90-100C, depending on the driving condition and it gets there within 5 minutes of driving, even in sub-freezing temperatures. This seems a little higher than what most of you here are getting, but it seems proper to me.

DieselAddict,

Yeah, that sounds a little high, but as long as it doesn't get over 100-105C in the summer it's perfectly normal. If you do see 105C+ temps in summer then something needs to be fixed. My cars also reach full operating temp in less than 5 minutes at 55mph, in sub-freezing temps; but stay in the 82-87C range when it's that cold out...


HTH,

Several folks mentioned their temps being 95C in the summer months ... while this is not "in the red" I believe it is higher than it should be.

I live in Northern Virginia - normal ops on mine is a quick warmup to 82-85C and then, if in very, very hot conditions in stop and go traffic, it may go to 90C ... as soon as moving above 25 MPG or so, it goes right back to 85 or so. It can be 100F plus and, while driving at 55 MPH, it stays rock solid at 82-85C.

Wasn't always this way ... after replacing the viscous fan clutch two summers ago, it started heating up past 95C and moving up and down ... replaced the thermostat and returned to normal ops running at 82-85 steady (literally no movement).

Bottom line - noticeable movement up and down and anything about 90C is likely abnormal ... take a look at your v clutch and thermostat.

I think some of the variation in coolant temp comes from people using varying thermostats. I believe these cars are supposed to have an 80C thermostat, meaning the thermostat starts to open at that temp and thus the operating temp would be in the 90's.

I too thought my operating temp is a little too high, but it's steady and only twice did it get a little above 100C on a hot summer day. Most of the time it's steady in the 90's. In the spring I plan to flush the entire cooling system and see if it makes a difference.

Even in fairly cool weather my engine runs a bit hotter when it is climbing steep grades at high speed. In the mountains in the summer, fully loaded and A/C on, I can get to 100c going up hills at speed. As soon as the load lessens the temp starts to drop. My car has been doing this for the 10+ years I have owned it without ill effect. As far as I know this is typical and won't hurt the engine provided it doesn't got into the red on the temp gauge.

May I be another to singthe praises ofthe Auto Zone Thermostat. Car came with NXXA knockoff was almost new. Following the advice of this forum changed to the AZ device and voila. Problem cured.

Thanks

Ditto on the 80 to 85 degrees C.

Folks, please don't get too caught up in expecting 80-85C temps as "normal". Believe me, I've been down this road ad nauseum in the past, both with my own cars and DOZENS of people on the MBZ.org email lists. The final consensus is ANYTHING above 80C and below 100C is perfectly normal. If your car runs 95C all the time with peaks at 100C in summer there is NOTHING to fix, don't bother with a different t-stat, or anything else. You only need to worry if under 80C ever, or consistently above 105C in summer. The "worry zone", IMO, is 110-120C. Sorry to beat this to death but not every MB diesel will stay parked at 82C (although SOME can and do!)

:cool: :cool: :cool:


Regards,