oooops, red face... - PeachParts Mercedes-Benz Forum

Piotr · #1 09-10-2002, 10:12 PM

Well, after advising a lot of people on overheating, it happened to me today. The day was about 92 F (33C), and I run my AC. after getting on the freeway (well, I wouldn't call the Blue Route that, but it is) I noticed my 190d was running at 100C. That has never happened, even with the AC on since I had the new compressor put in. As I progressed the temp climbed to about 105 C on inclines and dropped to normal 95-98C on level and downhill. After turning off the AC, the temp was normal no matter how fast or hard I drove.

I have a 1 year old t-stat, radiator, expansion cap, and no obvious leaks, but about 3 weeks ago I had to add about a pint of coolant. It's possible, that the upper radiator hose is leaking in a stealthy way. I'll replace the hoses, flush the system, put in MB coolant, and report back

#2 09-10-2002, 10:23 PM

Good luck.

190D22 · #3 09-10-2002, 10:33 PM

Piotr, my car went up to about 115C today sitting still, but slowly dropped on its own, then once I got moving (to about 45mph) the temp dropped quickly to about 85C. I had no AC running. Ambient temp at that time said 37.5C. Which is so hot my back was drenched (thank god my shirt was black!). Then on my trip home I had the AC on, only got to 100C at its highest, and was nice and cool in the car (no sweaty back!) ambient temp still around 37C. I'm voting for thermostat or fan clutch on mine. But not worried because it always goes down quickly. If I get worried I put the heat on MAX and it comes down nice and quick even at idle. It's also safe until its in the RED ZONE correct???? I don't think it's dangerous for the engine until it's at 120C. Why would they design it like that? Correct me if I'm wrong here.

psfred · #4 09-10-2002, 11:10 PM

They design them like that so you get some warning before you cook the engine. The temp gauge moves in a linear fashion on the MB, and usually they are pretty accurate. Coolant temps up to the boiling point of the coolant (under pressure) are fine, as the engine won't get too hot so long as the coolant is moving and liquid.

Don't overlook the radiator cap as a cause for coolant loss and running hot -- they fail by no longer sealing, so the system won't pressurize. Coolant is forced out into the recovery tank when it boils (usually after a hard highway run), and is then drawn back into the engine as it cools off.

Happened on the 300TE last summer. Sis blew the head gasket and rad on her Volvo on the way up, and I didn't get it fixed. PO on the 300TE remembered something about overheated, so had Sis watch when she borrowed the car for the trip to Cleveland. Sure enough, when she stopped at a rest stop, the coolant level light came on. Had a service station fill her up, then finished the trip with no AC. Never had a real overheating problem (but then, she never watches the guages, either!). I fixed the Volvo, drove up to meet her, then drove the 300TE home. Ran the AC the whole time, no problems, although it ran a bit hot (100 C) in Cincinatti. Boiled over when I stopped south of town, so I drove around checking out parts stores till I found a new radiator cap. Temp came right down, no more coolant loss.

Temp will still go up to 100 C in stop and go traffic, so supect the visco clutch, although it usually won't lock up til 110 C or so.

Peter

Piotr · #5 09-11-2002, 09:37 AM

Nate, actually, my temp gauge comes up to 115C in traffic and then comes down to 100C just as designed!That's when the fan switch turns your main fan on. Since yours does the same, you will learn after about $250 that your clutch is just fine,just likeyour switch, but it's your $$$. What I'm saying is that since I have a 2 year old clutch, I know all of the components I mentioned are OK. Because your 190 behaves the same (at idle)as mine, you don't have to do anything. Now if the temp comes up to 115C and continues to climb or stays there, I'd worry.

psfred, why would you suspect visco clutch if , as you said,it locks in (just like in our 190D's) at 110C, and your temp goes only to 100C???

Wasuchi · #6 09-11-2002, 11:53 AM

Do 190's have an electric fan in the front of the radiator a/c stuff? My 300D never gets over 105C even if I leave it running (sitting) with the a/c on max in the 100+ degree Texas heat. The electric fan blows like crazy, keeps it cool.

jobah · #7 09-11-2002, 12:38 PM

I have had this problem.

The problem may be that the magnetic clutch (on 1984's only) may not be engaging due to poor electrical contacts at the water pump electrical connection.

Hope this helps.

gsxr · #8 09-11-2002, 02:40 PM

There's no way the car should hit 115C when idling in traffic with the AC on. If it does, something isn't right. And yes it can be the fan clutch, it's worth verifying that the clutch is operating correctly. The OM603 engines have a mechanical clutch, which seems to have a life of maybe 7-10 years (translation: if it's original, it's shot.) I'm not sure if the 601/602 uses an electric clutch or not. But if it's the thermal hydro/mechanical type like the 603, definitely check it! The procedure is in the service manual, and other tests have been described ad nauseum on this forum (use the search feature.)

With properly repaired cooling systems, none of my 3 cars will exceed 100-105C when idling in traffic for extended periods with the AC on, in 100-110F ambient temps. Actually none will exceed 105C under ANY conditions that I have ever driven in! Usually they all stay well under 100C. Also, on my '87's, the electric fan high speed kicks on at 105C. Not sure what the switch is rated at for the 190's but I am willing to bet it's supposed to be a lot lower than 115C.

Final tip: Use no more than 1 gallon of MB coolant, and a full bottle of RedLine Water Wetter, and you may see a drop in temps.

Good luck,

#9 09-11-2002, 03:43 PM

I agree with gsxr at the sake of being unpopular on this thread. I don't know how much different my car is but since repl th efan clutch it doesn't go over 90 degress c anywhere, anytime, anyhow. When my fan clutch was bad, it would hit over 100, driveable but not good in my o.

Piotr · #10 09-11-2002, 05:29 PM

Tank, what gives you an idea you'd be unpopular???
Anyway, the 190 fan switch is rated 100-110C- it kicks in at 110C and stops when the temp goes down to 100C. The aux fan works always with ac or kicks in at 115C. that's not a problem. I'm running about 90-95 w/o ac (normal). the fans kick in like they supposed to, I think my temp sender may be miscalibrated (it's hard to determine if the gauge says 110 or 115). I have a brand new clutch (the old one was fine, too). what I was concern about was the fact that for the first time the temp climb above 100C WHILE DRIVING (75 mph) with the ac on. I just read the post that low refrigerant may cause more load on compressor and the engine, thus causing overheating. the car goes back to the guy who installed the new ac compressor,because I think I noticed the ac dye showing up under the compressor. if I have a leak, this would explain everything..

#11 09-11-2002, 05:42 PM

First time I have heard of the low refrigerant excuse, I will have to use that the next time I hook one into the trees from the tee box. Just kid'n.

When my overflow tank was a little low, meaning about 10+ centimeters below the max line, my car was hitting 110-115 also. It was just after I switched over to the mb coolant and didn't get all the air bubbles out right away. Didn't read all the posts but this could easily cause that too. I felt like an idiot after going through a huge expensive diagnosis in my mind before checking such a basic item.

gsxr · #12 09-11-2002, 06:26 PM

Actually, on the 2.2L four cylinder diesel (OM601) with magentic fan clutch, the service manual states the temp switch (S25/1) should close and engage the fan at coolant temps between 98-102C. Vehicles with AC have an additional switch that engages the fan based on a "52C temp switch" at the receiver/dryer (which sounds weird to me).

In the section describing the aux fan (83-560) it states it is controlled by a *pressure* switch at the receiver/dryer, which is what I expected (turns on at 20 bar, off at 15 bar). The first part may be a typo? Strange. But I can't find anything that says the aux fan turns on at 115C. On my cars it turns on at 105C, and I still think 115C is way too high. I'll see if I can find anything else, maybe in the electrical troubleshooting manual...?

gsxr · #13 09-11-2002, 07:07 PM

OK, I looked at the horrible PDF files on the 201 electrical manual - some sections are almost unreadable. The 84/85 models are different. Here's the scoop:

1984 190D 2.2L
Low speed fan is controlled by 15/20 bar pressure switch at receiver/dryer
High speed fan is controlled by 100C switch S25/1
Main fan magnetic clutch is also controlled by 100C switch S25/1

1985 190D 2.2L
Low speed fan is controlled by 15/20 bar pressure switch at receiver/dryer
High speed fan is controlled by 110C switch S25/5 (?)
Main fan magnetic clutch is also controlled by 110C switch S25/5 (?)

1986-87 190D 2.5L
Low speed fan is controlled by 15/20 bar pressure switch at receiver/dryer
High speed fan is controlled by 105C switch S25/5
Main fan clutch is mechanical, not electric, it engages at approx. 95C

According to the EPC, the part numbers for the 84/85 switches are different than the 86-89 switches, so there was some change there. I have found that the temperatures stated in the electrical manual are NOT always correct! The way to tell what temp the switch will engage is to look at the number stamped on the switch body itself, it will specify the temperature in degrees C. You can also compare the switch p/n to the p/n specified in the EPC to make sure the proper switches are installed on your engine.

Anyway, on a 1984 model, both the main fan and aux fan should be churning away above 100C. On 1985 models, it looks like both engage at 110C, but it's hard to tell for sure because the PDF is messed up. 1986-89 models appear to use the 105/115 switch that is in my car, which turns on the aux fan high speed at 105C and kills the AC compressor (overload protection) at 115C. I'm not as familiar with the W201 engines so I can't tell for certain.

But regardless, the fan coming on at 115C is too high, and besides the engine should never get that hot! I never have the aux fan high speed engage at 105C because my cars never reach that temperature.

#14 09-11-2002, 08:03 PM

Brilliant! Excellente! That's why I belong to this forum.

Piotr · #15 09-11-2002, 10:23 PM

Agree, TANK! Thanx gsxr!! I believe my engine temp sender is off, because the fans did start at 110C, and now they appear to be a little higher, but maybe not quite 115C.
I checked with the dealer (and on the switch) I have (and should have) a 100C-110C switch and , apparently, it's doing its job. I tried to replace a temp sender unit once and got all kinds of weird readings, so I got back to the old one. Also, it's possible the switch is going bad (3rd one in 2 years!!)

52C switch seems to relate to the cooled ac air (your cooled air temp should be around 55C as it enters the cocpit - always liked that word).

Thanx guys! I'll let you know what the ac guys will say. By the way, without ac today my temp on the freeway was 85-95C (I have a 80-90 tstat, that's why I think my temp gauge maybe off).