606 engine temperatures: What constitutes “normal”?
 

I inadvertently hijacked another thread, (http://www.peachparts.com/shopforum/diesel-discussion/92407-timing-chain-life-replacement-96-e300.html) so I felt it appropriate to start a proper one so that people searching the archives can find the suitable information.

My question is what other owners of 606-engined cars are experiencing as far as running temperatures during warm & hot weather. The reason for my question is that my particular car (a 1995 E300D, 124 chassis) runs hot in comparison to my 123 300D (I know, I know, apples to oranges.)

Specifically, it runs at ~85 degrees under normal, low load & low ambient temperature conditions. It will go up to about 90-95 going up a hill, but that doesn’t concern me that much. However, when it is warmer outside (80-90 degrees), the car runs between 95 to 102 at high freeway speeds, and I’ve seen as much as 105-107 when puttering around at slower speeds. (AC use doesn’t seem to affect it very much – although the electric fan is actuated with the freon pressurization or temp rise, well before the coolant thermo switch kicks the fan into high speed.) I’m a little afraid of what will happen later this summer…

The car has a relatively new radiator, and I cleaned out the fins on the condenser & radiator when I first got the car. I replaced the thermostat when I did a flush (exact same results). The thermo clutch *seems* to be working properly, and the temperature sender is not to blame, its accuracy verified with an infrared thermometer.

One way to get the temperature down a bit when in “city driving” mode is to keep it in a lower gear & have the engine spin a little faster, thus pumping more water through the engine. (I recognize that it also increases the fan speed & pulls more air through as well) However, it seems as though there is plenty of relatively ‘cooled’ water in the radiator, but there isn’t enough water flow from the pump. (I’ve checked upper vs. lower hose temperatures when the car is really hot, and the lower hose is considerably cooler.)

Either this is ‘normal’ behavior for a 606 engine, or perhaps… I have a strange theory. I am wondering if maybe the water pump vanes have deteriorated due to cavitation, and therefore it isn’t pumping the amount of water per design specs. I also recall reading something somewhere about plastic impellers on a Mercedes engine, but I don’t recall which one (a search returned nothing). Either that, or the engineers cut it *really* close on the specified pumping volumes, trying to avoid parasitic losses & increasing the mileage a bit. What do you guys think???

Thanks Again!
RTH

I think it's caused by your screen name...

No, seriously. I had a 606 turbo in the 210 chassis, so we're comparing two different types of apples. However, it pretty much sat on ~82 all the time. Highway, city, stop and go in 105F heat, it didn't matter. Don't think I ever saw it hit 90. Of course, I never tried driving it up a mountain during the summer either.

I like your water pump theory. I think the plastic vanes was a BMW problem, not one of ours. I would also look into a good citric acid flush of the engine/cooling system - you could have scaling problems causing it to run hotter.

- JimY

I share your "laboratory setup" with the '95 E300D and a '85 300D. My 300D rarely hits 80. It usually sits right below that. I'm convinced that I need a new thermostat because I'm concerned that temp is too low.

By comparison, I was watching the temp guage on the E300 in stop/go traffic with AC on. It would sometimes hit the 100 mark and slightly over. However, at prolomnged cruising speeds, it settles at the half-way mark between 80 and what i'm calling 100.

The engine gets a lot hotter than the 300D. If I let the 300D sit for a couple of hours, all the heat has dissapaited. Do the same with the E300 and the temp is 80 or above... Much slower to cool off.

When I had my 500E, I used to open to hood to let the heat out once I had her parked in the garage... IT may be the encapsulation panel underneath which keeps things toasty under the hood.

Gilly posted something a long time ago about water pump vanes coming loose from the shaft on 606 engines. Mine was rock solid at 80* like jcyuhn's for 4 years. But this past year it has gotten somewhat erratic. It sometimes goes as high as 100, but for no apparent reason, and then it might run for several days without going over 85. I haven't gotten around to isolating the cause yet.

my car is an 84 300TD- 123

I don't know about your water pump theory, as my car just had a new water pump and a new Behr (OE) radiator, and it still exhibits similar behaviour to your (admittedly different engined) car-

I am thinking that the thermostat (only a year or two old, but installed before new rad and H2O pump) is the culprit-

-JAS

On the contrary I was thinking my engine runs too cool.

IT usually sits at around 80, +- 3 degrees. Hottest it's gotten in th esummer during my knowledge is about 90. In the winter it was running mid to high seventies..

I'll just be happy. Running a little cooler is better than running a little hotter I guess.

Gonna change the thermostat and fluid soon.

BTW. How many gallons of MB antifreeze are required when doing a fluid flush? I know it's a 50/50 mix.

Jim Y.: The screen name was apropos when I got it – the overheating in my1984 300D was eventually traced to a leaking headgasket & a slightly cracked head. She runs coooool now, but…

Michakaveli: …But not as cool as yours – yours should sit just above the 80 mark, so either your thermostat is off, or your sender / gauge is slightly off.

Mark: I whole-heartedly approve of your “lab setup”. :D Interesting to note that your lab animal has very similar characteristics – either I’m worrying about nothing, or we both have something to be concerned about (Jcyuhn’s temperatures look much more appealing to me, even though it’s a different chassis & a turbo engine.)

Rick: Spinners…Ugh. A blatantly stupid thing for rims, but a helluva lot worse for a waterpump… I tried searching, but couldn’t find anything in the archives. Do you recall if it was something inherent to the 606 engines specifically?

Meanwhile, the saga continues – today it was in the mid-80’s ambient, and the car was running anywhere from 90-102 depending on conditions. I also neglected to mention that I have been losing a small amount of coolant on a consistent basis, but I don’t have a pressure tester to isolate it. **Full disclosure: There was a note in one of the dealer service records regarding a “coolant seep” at the head gasket (external, obviously), but that note was made almost 200,000 miles ago, and the car has been living with it ever since.**

I certainly hope that this isn’t “deja-vu all over again” and it ends up being the head gasket (and/or head!?) like on my 300D.

Thanks to everyone for all the help!
RTH

Oops, I credited Gilly, when it should have been DR. DIESEL. The post I was talking about is here.

If your engine is running too cool (under 80C) with a recent thermostat, replace the temp sender in the cylinder head. They can start reading low when they get 10+ years old. At $10-$15 it's a cheap fix. I had that problem on my 1984 300D with it reading 10-20C below actual.

RTH, coolant loss is not a good sign! That may be part of the issue. The fan clutch can be very hard to diagnose, but try this. With the car cold, drive it for a few minutes to get the temp up to about 80C. Pop the hood, watch the fan blade, and kill the engine. It will probably freewheel and spin 5-10 times or more before stopping. Now go get the car HOT, like 100C or above on the gauge. Pop hood, kill engine, the fan should stop within 2 revolutions - or at least stop a LOT faster than when cool (uncoupled). The "roar" test doesn't apply to the new plastic blade OM606 fan, at least it never works for me but the "counting the turns" test should give some idea of how things are.

:D :D

Rick: Thank you for providing the link. Interesting indeed. If I end up pulling the pump, I’ll update this thread & the other one to indicate whether or not the early 606 has the plastic pump impeller.

GSXR: Yes, the coolant loss is a concern, although it is a comparatively small amount. I already replaced the 9 year old coolant cap just to eliminate that as a possibility. Regarding the fan clutch: I know that the “roar” method doesn’t really tell the story on these engines, so I previously used the “imbecile” method (don’t ask) & found that it was significantly more resistant to being held back when it was hot. However, I’ll definitely utilize your methodology in checking the fan clutch later today. Thanks again!