OK If I get down that way I'll check and report back.
Say, gsxr posted a picture of his water pump, one of them that is, out of an '87 300D - the steel blades on it were almost gone! it was rusted beyond description. I hope yours isn't.
Warning! pictures are pretty graphic and if you see them youmight not sleep well. Didn't you change your pump? if so, disregard the above.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

I to have had an ongoing running hot issue with my 87 wagon.
While driving up I-70 west of Denver to my home in Evergreen,(6%-8% grade) 5400ft msl to 7900ft msl, at 70mph a/c on, oat 50-80 degrees, the car will slowly warm up to 115c,

I have done the following with no significant change.

1)Drained and cleaned the cooling system per MB recomendations including citric acid
current mix 60% water,40% MB coolant, two bottles of Red Line water wetter
2)New Baer radiator
3)new thermostat
4)new clutch and fan
5)new water pump
6)replaced fan switch with lower temp spec
7)electric fans work when they should
8)cleaned everything
9)new auxheat pump( not really related)
10) Used laser thermo to verify actual temp, and water in VS water out , about a 25c drop,
After all of the above very little improvement, I have not had a really hot day yet, but I am worried, other than climbing this hill the cars temp is rock steady at 85 degrees, the ALDA has been turned up from the factory setting 2.5 turns very little smoke and generally runs very strong, 28mpg. Have I overlooked anything?,
Thanks
Ron

You have really gone over that vehicle and changed every possible area of concern.

As best as I can tell, there is nothing else.

If all components are performing to spec, this would indicate that the 603 cooling system cannot keep up with full horsepower output. Eventually, the engine will overheat if held at maximum power for sufficient time.

How long did it take for the engine to climb from 90°C. to 115°C.? Did 115°C. seem to be the maximum, or was it still climbing at that point?

I have had this one at maximum continuous power for six minutes and it reached 105°C. Ambient was about 75°F. However, maximum boost is only 9 psi. If you are dialed up higher than this, you introduce more fuel and put out more heat.

There really is no great concern. Just slow the vehicle down to 50 mph. The engine will run much cooler. I wouldn't run a 603 all the way up to 115°C. That's just playing with the 603 head gods.

Thanks Brian, I did not make any adjustment to the turbo, just to the alda, the car has lots of power, but does not seem to be overfueled or overboosted, I believe the factory spec is .9 bar or about 13 lbs of boost with the over boost protection at 1.1 bar. No apparent increase of temp during hard acceleration or at 100+mph on the level.
The hill in question is about a 10 mile climb and about half way up the temp is climbing to 110c the last 5 degrees to 115 happens last couple miles prior to the top. Problem is I have'nt seen a really hot day yet. Will see.
Thanks,
Ron

Something ain't quite right, IMO. When at full song, the cooling system should be able to keep up. My EGT testing put one helluva load on the engine (and got EGT's up to a kind of scary 1425F for a while) but the engine temps, AFAIK, didn't exceed 105C.

Some things to consider:

1) Are the condenser fins COMPLETELY clean - particularly in front of the fan clutch?
2) When the engine is reading 110-115C, can you pull over and make sure the electric fan is on high, AND that the fan clutch is solidly engaged? (Shut off the engine with the temp over ~100C and the fan blade should stop within 1 turn.)
3) Pull the water pump and inspect the housing. If pitted, replace the housing. This is a common problem with OM61x engines, but I haven't heard of a 603 having this - maybe yours would be the first?
4) Out of curiousity, did you get a DEALER rebuilt pump? The newer pumps have slightly deeper impeller blades, at least the one I bought from the dealer a few years ago was a couple of mm different than my original. (That rusted pump was not my car, btw!)
5) Try another NEW thermostat - preferably an OE/dealer unit. I know one person that got 2 (?) bad t-stats in a row before the third one cured the problem.

After that I'm starting to run out of ideas...

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

Dave, I believe the final variable is time. This hill is 10 miles in length. So, we are talking about 10 minutes under very near maximum continuous power.

In all of your EGT tests, you were doing 1/4 mile runs, correct?

Not enough time at full power to see what the cooling system will do, IMHO.

Additionally, it would be nearly impossible for the thermostat to be the culprit unless it was not fully open at 105° C. Highly unlikely.

Did you block the EGR with a BB? I know this suggestion is not popular on this list but try the same test without the BB. I too live at high altitude and have noticed about a 5 degree lower temp w/o the BB. Still not enough to explain your temps. If all else fails, and the temps remain high, be sure to idle the engine for a minute or so after running heavy boost. I've tried to make that a part of my cool down, turn off sequence.
Oilyrag
1987 300d Turbo 140K

Thanks Dave,
Well, I have put in two dealer thermostats, no change
Everything is clean
The water pump was a dealer purchased, factory reman,
I actually thought that the orginal pump might have been the problem, noticable corrision on the impellers, the dimensions of the impellers looked to be the same, the housing looked fine.???
Also replaced all radiator hoses.
I have checked that the electric fans come on high and that the clutch and fan are fully engaged at the high temp, 110-115, the clutch and fan does stop immediatly when the engine is stopped.

I really like this car, it runs excellent and cool when not climbing this hill, and the fact summer is on the way and with all of the talk of the famous #14 head and its propensity to crack, I figured I should try to bring down the temp, I feel very confident that everything is working as it should, but it still is disconcerning.
Thanks again
Ron

ohcaptainron,

I was wondering if you have had the coolant checked for combustion gases? Perhaps there is a blow-by of combustion gases in the head gasket that is causing the engine to overheat under load. When combustion gases are causing an engine to overheat it is usually most pronounced on hills or when the engine is under heavy load. I would have to say your overheating problems sounds a bit worse than mine. There is some sort of chemical test that mechanics use to check for combustion gases in the coolant. Usually the engine still runs fine.

I think on my 1987 300TDT the only thing left to do is change out the water pump. I will cross my fingers and hope that is the cause of the overheating problem.

-Steve

__________________
1987 300TDT smoke silver w/ burgundy leather interior
2000 VW Passat wagon indigo blue w/ beige leather interior
1985 Mustang SVO
1970 Chevrolet K10 fleetside, shortbed

Steve, thanks for the reply:

In short I have not done this test, the radiator hose is soft over night, there is no apparent loss of coolant, but on the other hand I cannot explain why its running hot, keep in mind that the car has never overheated just runs in the 110-115 range after a long climb, otherwise it never gets over 90. I think I will have someone do the test just to make sure, God knows I have done everything
else. Thanks for the suggestion.
Ron

Its normal for an engine to get hotter on a long hill because it is burning the maximum fuel consumption. If you ran up a long hill, you would get hotter too.

I saw my '80 300SD get up to 260*F in CA on a long hill where there are signs saying to turn off the AC. The temp guage was just touching the red area. No coolant was lost and the engine cooled to normal as soon as I started the down grade.

This didn't worry me a bit because it was within the temperature limit on the guage.

P E H

gsxr,

I was wondering if the OE water pump is better than one made by LASO or GRAF? Does one of these companies make a the OE water pump? If the OE water pump is better, I will just get one of those.

Also the new thermostat that was put was a Wahler brand, as opposed to the OE one. I am wondering if it is worth spending another $30 on a new thermostat?

Thanks,

-Steve

__________________
1987 300TDT smoke silver w/ burgundy leather interior
2000 VW Passat wagon indigo blue w/ beige leather interior
1985 Mustang SVO
1970 Chevrolet K10 fleetside, shortbed

Don't know about the waterpump but regarding the thermostat, don't waste your money. It either works or it doesn't. If it closes at the right temp and open at the right temp, it's good. period.

Thanks
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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Brian, no, for my 1/4 mile runs the EGT only reaches 1000F. Read the thread at the link I posted above for more details - I was at absolute maximum output for about a minute. I seriously doubt the long hill climb is anywhere near max output but the time factor is definitely something to consider. If it doesn't go *over* 115C, I'd probably forget about it, Ron.

I wonder if there might possibly be a partially blocked exhaust (plugged catalyst)? That's not exactly easy to test though.

About the t-stats, there's some possibility that a cheap aftermarket unit may not have the full stroke of a real OE part. And there's also the possibility of an OE unit not working properly out of the box. If you have the time and facilities to properly test it - measure temp at start of opening, full opening, and make sure it's getting fully open that's great. If not, there's really only one way to test - replace with another. You can always pop the previous good one in the toolbox, the t-stat should really be changed every 5 years or so as preventive maintenance (new t-stat $30, new engine $6000, you do the math.)

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

I Have a 83 300SD that I have been fighting that very same problem of getting hot on long grades. I bought it second hand with no history, so after reading many posts I checked the obvious. The Thermosat was gutted (one hint on the PO's service standards) but after checking the function of a new Thermosat, flushing coolent and replacing MB coolent, checking fan, replacing radiator, I found the culprit to be the aftermarket waterpump. I replaced it with OEM with was a machined vane type. The exsisting one was the bent metal vane type, which looked to be in good shape. Was this an aftermarket or just for a different engine? Anyway, the engine now after many months of tinkering runs in the 80-90 range on long hills. BTW anyone need a good used radiator (Behr) ?

Jim