Car running @95 C = 203 F !!!!!!!!!!!!! - Page 2 - PeachParts Mercedes-Benz Forum

Ken300D · #16 03-09-2003, 07:00 PM

Rick:

Did you get your new thermostat from the dealer?

Seems there was a bad production run of thermostats - and they all went to dealers.

I'm serious - I've been following the issue now for over a year.

Get your thermostats from anyplace but the dealer.

Ken300D

rickjordan · #17 03-09-2003, 09:02 PM

Actually I got it through Fastlane. It was the same exact model, temp., etc. that was in the engine.

PaulH · #18 03-09-2003, 10:19 PM

It seems that MB diesels built after 1985 run hotter. When I bought my "87 SDL (new), it ran about 88-92C on the open road, (Don't remember the city temps.) Last summer I got a new water pump, t-stat, and much needed fan clutch. Now it runs at 88-92C on the open road (even in 20F weather) and approx 98-103 in city traffic in 100F summer weather. According to published specs, the aux fan doesn't even click on until about 105C ! My 1987 (SDL) manual and my 2000 (ML, gas) manual state - and I quote from the manual: "During severe operating conditions and stop and go traffic, the coolant temperature may rise close to the red marking." The 2000 manual goes on to say don't run the engine in the red marked area. I figure that the temp. gage may be off about +- 5C. Also, in commerical truck diesels, a hot diesel is far more efficient than a cool running one. Of course, what we are all discussing is what is too hot. Now, if you are running 105 - 120 C on the open level road, I'd say that you have a problem.

rwthomas1 · #19 03-09-2003, 11:17 PM

Rick,
If the car runs at the 95C mark and never gets any warmer or boils over I don't see why there is a problem. 200-205*F is not that hot. With a cast-iron engine you don't really have to worry until 245*F/120*C so don't sweat it. You could have several issues here. The T-stat might be slightly out of spec, the gauge/sensor might be slightly out of spec, the radiator may be getting tired. Drive it, keep an eye on the gauge and enjoy your MB. RT

psfred · #20 03-11-2003, 06:48 PM

My "Big Benz" runs at the halfway mark between 175 and the red zone in traffic, but if I open the hood, the radiator won't be very warm. I've concluded that either the new t-stat isn't 75C or the temp gauge is a bit off. More likely the later, it's 31 years old.....

Peter

Stevo · #21 03-12-2003, 11:57 AM

I have heard that "if you can hold the upper radiator hose w/o discomfort its NOT to hot" I have pulled over a couple of times when I thought she was a little hot and used that test.

BTW my gauge needle used to jump around now and then. I changed the temp senors and that fixed that.

irianjim · #22 03-15-2003, 09:01 PM

For what it is worth, I just finished a road trip today in my 81 300D and the temperature sat halfway between the 80 and what think is the 100 mark. So I was running about 90 degrees at 70 miles an hour. I thought that was ok - but now you guys have me worried! I just went out and checked the coolant and it is fine. The only time it ever operated above that point is when my water pump failed and I had to repalce it.

I'll just keep an eye on it as the summer gets here, but I'm inclined to think it is ok.....guess I am just paranoid!

mrbill240D · #23 03-17-2003, 08:32 PM

Something I found with my 82 240D was that the Temp gauge reads high. It reads about 15C hotter then it should. Checked this with hot water, candy thermometer and a new and the old sending unit. Hooked up sending unit(s) to engine wiring then put sending unit into hot (160F to 200F) water then checked gauge and found gauge to be the problem not engine or radiator. This of course was after I tried everything else I could think of and spending lots of Money. So maybe it would be wise for you to check and make sure your gauge is actually working correctly before replacement of many expensive parts. Learn from our mistakes that’s what its all about.

Bill

ltrain300D · #24 03-17-2003, 11:20 PM

If I'm not mistaken, on the 300D turbos, the thermostat doesn't reach its "fully-open" position until_94°C. Mine runs right around 90 to 93 in 85 degree Florida weather under normal driving conditions. I wouldn't get too worried about 95°C.

lrg · #25 03-18-2003, 01:51 PM

Rick,
As long as your car can handle pulling decent hills in hot weather don't worry about it. You likely have a bit of air in the system that will probably work it's way out. There are so many places that things like the sending units, gauges, thermostats, etc. can be a little bit off that you can drive yourself nuts trying to get your car to be just like everyone else's. Ultimately, if it's not overheating in hot weather under heavy load you have no problem. Unlike gassers that can get preignition problems if they run a bit on the hot side, diesels actually like it.

Jassper · #26 03-19-2003, 01:22 AM

Once I read in a newspaper that operating temperature of 80 degrees is a good one for a petrol engine, 85 is even better, considered perfect. Diesel engines have their operating temp 5 degrees higher than petrol engines- that would make 90 degrees.

With our new 280E the operating temp, indeed, was 85 steady. No matter what the driving conditions were, it had 85 degrees. Now 10 years later the temp rises a few degrees but doesn't exceed 90 degree mark (unles driving in stop-and-go traffic, A/C on etc but that is considered normal).

My 250TD (2.5 Turbo) has its operating temp 85 degrees also when driving in a standard way, though the temp climbs happily to 90-95 in hot summer days, even 100 in stop-and-go traffic. I don't consider this to be a problem, diesels run hotter than petrols, 90 is by all means a perfect operating temperature and variations (95 degrees for example) are a part of running the engine under daily conditions.

Mind that a new petrol engine will run 100 degrees and more when the day is hot and your A/C is on and you hardly move on in traffic. You are only to start worrying when the temp does not go down when your cooling aids kick in or when the temp does not go down when you start moving, allowing more cooling air past the radiator.

#27 03-19-2003, 01:48 PM

Hey folks,

Ya know I played with the thermostat too much and broke a bolkt off in the housing. ALWAYS USE NEW BOLTS AND ANTI SIEZE.

I wanted it to run cold in the summer and warm in the winter. And while changing out the thermostat *#$&#(*%&@ I broke the bolt off.

That was no fun.

Now I have it at about 90 and if it goes up to 105 I will accept it. I would rather have heat in the winter.

Cleaning the fins on the radiator helped out alot but becareful I broke that too.

Bye

bob c

gsxr · #28 03-19-2003, 02:55 PM

I've said this so many times I think I'm a broken record: If the gauge temp is above 80C and almost never exceeds 100C, that is NORMAL and don't waste your time or money chasing down a "problem" that doesn't exist.

The thing to look for here is minimum temp of 80C, if it's too low, the problem is most likely a bad t-stat and/or the sender in the head. The senders, when they get old, sometimes read too LOW. A new one is $10, I've replaced them on all my cars as cheap insurance. The other thing is max temp on the gauge under severe conditions - usually the hottest day of summer with A/C on max. Most cars should stay in the 100-105C range here and not get above that. 110C+ may indicate a problem, but regardless the danger zone is 120C+ if your rad cap is ok.

Different engine t-stats (yes, they ARE different for 616, 617, 602, 603, turbo & non-turbo, etc) have different specs. Just because it's rated to BEGIN opening at 80C (like my 603 turbo) does NOT mean the gauge should read 80C! They're usually full open by ~95C, the specs are in your MB service manual - go read it. If your car is running too hot... i.e., 100C+ most of the time, yes there is likely a problem. And yes on the OM61x engines there was a recent discovery by Bruce on the MBZ list that the t-stat housing can corrode and prevent the bypass from sealing off, making the car run hot even with a good rad, t-stat, and fan. Replacement of the housing (~$100) is the proper cure although he did a t-stat modification which also worked.

And of course each car will be different due to a zillion variables. For reference, my W123 with an almost completely new cooling system runs at ~90C year round. Maybe a smidge cooler in winter, but never above 95C in summer, ever. Is 90-95C too hot? NO! IT IS NOT! (deep breath) My one W124 with the new head, and also totally new cooling system, stays parked at 90-95C year round, same deal. I have seen it hit 100C a couple times in 110F ambients or climbing a steep grade, but that's it. Same deal - it's NORMAL. My other 124 has a cracked head/gasket and although most of the time it runs at ~83C, it fluctuates a lot more, popping up to 95-105C at times when it really shouldn't. I don't worry too much because I *know* what the problem is, I just haven't fixed it yet.

In summary: Please don't expect YOUR car to run at 80-85C and freak out if it doesn't. BT, DT, spent the last 5+ years learning this the hard way. Please do change your coolant every 3 years with MB anti-freeze only, make sure the rad cap is good (1.4 bar), and the radiator fins are clean on both sides.

BTW - my post is referring to all MB diesels only, OM61x and OM60x - not gassers.

Regards,

#29 03-19-2003, 06:18 PM

TTT

84300DT · #30 03-19-2003, 06:21 PM

Quote:

Originally posted by rickjordan
Recently changed the thermostat in my TD, which was causing the car to run at a mere 60 C. With the new OEM Behr 80 C thermo., she is now running at about 95 C. I recently figured out what that is in F., 203 degs. That is hot, but apparently not for these engines, because the red line is up at 120+ deg C, which is something like over 220.
Is everyone else running at this temp? Here it is I thought diesels ran cooler than gasoline engines, but I guess I was wrong. My VW Passat with a 1.8 liter turbo runs at a solid 190F.

rick, the real test would be to bring it to the new england gtg
this saturday