Max engine temp under load - Page 3 - PeachParts Mercedes-Benz Forum

gsxr · #31 06-10-2002, 09:04 PM

Hi Steve,

Glad you fixed it! Something I didn't think of before was that a failed fan clutch could replicate symptoms of a bad radiator. Here's how: If the clutch is OK but just never engages (to spin faster than ~1500), it would cool OK at idle but not under load and/or when really hot. BUT, if the clutch was totally shot, and wasn't even matching RPM's up to 1500 then it would barely pull any air at all, even at idle. It would be kind of freewheeling all the time. That would cause hotter operation at idle. I wasn't sure if the clutch could or would fail like that, but I suppose it's possible, and your experience somewhat confirms it. But anyway, if it won't exceed 100C under most conditions with warm ambients, I'd say you are all set! Congrats!

Best regards,

#32 06-10-2002, 09:40 PM

My temp gauge starts at 100f and has intervals for 175 and up to 250 were the red line is...i hear some of you talking about 80 - 90 degress. When im driving it usually reads between 100 to 110.
Its a '79 240D...is this a normal operating range, im in the south(NC) Hot days so far this summer and the AC is not working.

#33 06-10-2002, 10:15 PM

Hi PSetzer,

Your guage appears to be in Farenhiet while ours is in Celsius.

(F-32)/1.8=C

so...

(212F-32)/1.8=100C water boils
(175F-32)/1.8=79.4C

(100F-32)/1.8=37C (accuracy unlikely?)

BR,

Steve (8C>

#34 06-10-2002, 10:21 PM

Quote:

Originally posted by gsxr
If the clutch is OK but just never engages (to spin faster than ~1500), it would cool OK at idle but not under load and/or when really hot. BUT, if the clutch was totally shot, and wasn't even matching RPM's up to 1500 then it would barely pull any air at all, even at idle. It would be kind of freewheeling all the time. That would cause hotter operation at idle. I wasn't sure if the clutch could or would fail like that

Hi Dave,
I think this was exactly the case. The fan was just there, had little or no resistance.

I guess it's all about flow. Air flow AND coolant flow. I would say that the right combination of either could mimic the behavior of the inverse amounts. I mean to say that poor air flow and ok coolant flow can offer the same symptoms as poor coolant flow and OK air flow, under some conditions.

At any rate, I am very pleased so far and have the fingers crossed. Thanks again for your suggestions...

BR,

Steve (8C>

msyoder · #35 06-10-2002, 11:01 PM

Steve,

Excellent! This is the same result I'm hoping for. I think that my clutch is doing just that kind of intermediate behavior. It wouldn't freely spin at idle (I tried to stop it with a bald up paper bag), but it would free spin for 10s of secs after engine shut down.

At 3000 rpms it would finally sound like it was roaring a bit, but would never stop when it reached the upper limit.

Hmm, my wife put a lot of miles on this car without me last summer. She was also the one who first experianced the coolant loss that was the first symptom of the head being cracked. I even got it close to the red-line once my self the summer before.

Well, that's a shame. I wish I had tested and replaced this fan when I first got it.

I'll be really good at owning one of these when I'm finished with this one.

Ridge · #36 06-11-2002, 06:03 PM

Gentlemen,

It's been awhile since I read all this thread so bear with me if someone else has already made this suggestion. My son has been literally sweating this problem out on his favorite 300TD and after going through everything, he comes to me and informs me that he's found a sight crack in the plastic pressure tank. Then I realize that he's been fighting an unwinnable battle.

So if any of you are having a similar problem, do a pressure test on your system first. If it fails holding pressure, look around the filler neck on the plastic tank. Bet you'll find a crack. New tank, new pressure test, pass, problem solved.

Ben

msyoder · #37 06-23-2002, 11:37 AM

Folks,

We'll it's completely confirmed. My overheating problem was directly caused by a failure in the viscous fan clutch. Today was hot in NYC (100 deg. indicated on the dash temp gage). The engine temp never passed 100 deg. C. even while sitting in traffic and running around at low speed.

The next real problem is weak cold air from the AC. Last week I had it recharged to no avail. Nick, my independent, looked at it again today and claims that the problem is the expansion valve. He came to this conclusion by watching the pressure gage he connected and taping on the expansion valve with a large screw driver and seeing the pressure drop momentarily.

He was measuring from the Schrader valve on the cold side (driver side by fender) and it was between 60 & 80lbs. He said he expected 40.

He says this is a four hour job, ouch. Does anyone have an option of about this problem. Any one have some way to confirm his diagnoses? Or better yet, a trick to try and coax one more summer out of this valve?

Thanks,