So I read about all the troubles about bolts breaking and heeded all the advice I could about penetrating oil and all that, and you guessed it, the left bolt broke.

Well, anyway, I got the others open, got three new bolts from the FLAPS and did my damndest to get that bolt out. No luck. Called my mechanic who told me to put in the two bolts, bring some water with me, and drive to his place tomorrow morning. I guess he has the tools to do the deed.

Anyways, the topic really is about the new t-stat. I took the car out for a spi to test the t-stat. Miraculously, no leaks at all, mind you, with just two bolts, although i would be loath to drive my usual commute tomorrow.

Well, the temps took a long time getting there, but when they did...this is where they sat at!!


The strange thing is, the lower rad hose is cool to the touch, the upper is too hot to touch. The infrared thermometer reads 69 for top one, and just about 30 for bottom one. The T-stat housing attached to the engine is 55 and the outer one is 45. These are all in degrees centigrade.

The background info is, I've noticed the temps climbing up almost to that middle mark (100 degrees C?) on some strong uphill climbs lately. Plus the fact that the housing seemed to be leaking from the top with cruddy deposits on the seam.

So I thought I would change it all out. Previously though, the temps would usually sit closer to the 80 mark, or rather 5 mm above it to be precise. It would go up on steep hills and return to the above 80 mark in regular grades.

Now though, it went right up to that closer to 100 mark and stayed there, even after idling for 5 mins in the driveway.

What should I do? Return the new one (I doubt if it can be returned since its used already and put back the old one? Flush the system? Live with it as this is where its supposed to be?

Any and all thoughts, much appreciated, thanks!

__________________
1987 300TD
1984 300D
755,000 KM and going strong
BC Canada

Air still present in the coolant circuit? Refill the coolant system as recommended in the archives for your model?

Be sure that you have ALL of the air out of the cooling circuits.

OK...air...never thought that would be a problem. I did all work with the car raised on ramps, so I thought, no problem. I have purged the system before in the same manner with no overheating before.

I will do it again later. After all, I'll have to open it up again at the mechanic's to take out the broken bolt still.

But am I right in saying that the temps are too high?

__________________
1987 300TD
1984 300D
755,000 KM and going strong
BC Canada

Yes, the temps seem to be trending towards too high, but the question is, why? you have already replaced the t'stat, so double check the air purge.

It is also possible that you have a marginal radiator, and it will need to be cleaned or replaced. If you can, check temperature distribution across the radiator, which should be uniform. If you find too many 'cold' spots, you need to clean/replace...

Just to play devils advocate, why is that too high? Does the tstat not dump open and hold it at 100c? You actually get a very slight boost in efficiency as you run the engine hotter (until thermal expansion causes the pistons to wedge in the cylinders).

__________________
OM617 in a 67 chevy pickup http://tinyurl.com/projectgmbenz

Well, here's my observation over the last few days. First order of the day was to get to the mechanic's where he welded a washer to the small bit of bolt still sticking out and we got it out in short order.

Then I reinstalled the new T-stat. And made sure to burp the system good, and guess what....that's right, same temps.

My mechanic looked at it, and said, well, that's a good temp for diesel! Well, I was kinda nonplussed, but thought, ok, he should know better. The only thing is, ever since I've owned the car, the temps have always been in and around the 80 mark.

What I've found now, is that it warms up quicker, then once it reaches that point (just below the 100 mark) it just stays there, regardless of load. I'm beginning to think that this is the optimum temps for the engine, and that my old t-stat was just broken. I understand that when they break, they break to cool right?

Anyways, I don't believe its anything to do with the rad, as its practically brand new (broke the nipple on the original one), and I don't think I have any problems in the heater core, as there's lots of heat coming out the vents, so what could be my (imaginary) problem?

__________________
1987 300TD
1984 300D
755,000 KM and going strong
BC Canada

If you still have the original thermostat sit it in a pot with a thermometer and see at what temperature it opens. Probably lower than it should. Your faster warmup now kind of indicates the old unit was bad anyways.

Cripes...I threw the old one out at the mechanic's. Does anyone know if the temp I am indicating is correct?

__________________
1987 300TD
1984 300D
755,000 KM and going strong
BC Canada

It's higher than typical.

No way of knowing if the temperature indicator is accurate either. Some testing to establish might help verify this. IR gun temperature readings perhaps.

As long as it does not boil over the engine should be able to operate okay. This is not an engine type with a demanding aluminium head. A little higher operating temperature if present is not all that bad.

Do you know what temperature the new thermostat is rated for? Some thermostats have a small hole on the outer ring and if yours does you want to put it in with that on top.

__________________
1983 300SD
200000miles

It's quite common for an MB to run a little warmer with a new thermostat. This is because these stats fail open.

__________________
2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

Wait...if it failed open, then wouldn't it be cooler? If it failed closed, then it would get warmer right? And if so, wouldn't it just get all the way up there into serious heat?

What is, actually, the range that its supposed to be?

__________________
1987 300TD
1984 300D
755,000 KM and going strong
BC Canada

It's a relative thing. If the old thermostat failed open, a new and presumably functional thermostat would yield a warmer temperature.


I have owned an '82 300D for almost 20 years. It has consistently run 85 degrees except in really hot summer temps with the a/c operating, at which time it will approach 100 degrees in city traffic. (You won't see those ambient temps in BC.) And that has been with three different thermostats, two water pumps and two radiators.