Too HOT need help - PeachParts Mercedes-Benz Forum

Jkoch · #1 05-07-2007, 06:05 PM

1983 380SL is getting way too hot. Flushed with new thermostat this week. Runs about 100C going down the road but idling it shoots up to Red line.
Fan clutch seems to spin when hot with little resistance. Can can spin it about 1/2 spin with one hand when hot. Not sure what is the best way to determine if this is the problem.

One mechanic told me it was the Head gaskets but another told me that is not correct. Very confused and have been ripped off by the last mechanic so looking for my own solution.

Any help in troubleshooting would be greatly appreciated!

G-Benz · #2 05-07-2007, 09:11 PM

Head gasket issues are usually accompanied by contamination in the coolant tank (i.e oil) or oil seepage, and even loss of coolant as it invades the combustion chamber...the exhaust might tell you that. Otherwise, your head gasket is fine.

Sounds like your fan clutch is okay as well.

When is the last time you changed your coolant tank cap? If it can't hold pressure, your temps will go up dramatically.

If your temp sensor is bad, it may not turn your aux fans on when necessary. Do you run your A/C during this time? Do your aux fans run when your A/C is on? They should. The A/C condensor parked in front of the radiator is generating a lot of heat, and without the aux fans, your radiator temp starts off hotter than normal.

Some inexpensive suggestions in case you decide to start by throwing a few parts at this problem...

dkveuro · #3 05-07-2007, 10:33 PM

Again for emphasis.

Mercedes Engine Coolant Temperature.

It is normal for the temperature gauge to read close to 120C after coming to a stop for a few minutes with engine running, especially in high ambient temperatures.

Provided the coolant is not being discharged from the system, this can be concidered normal providing the coolant temperature drops to 80C to 90C back on the road.....or words to that effect.

I have seen many customers vehicles running slightly higher temperature readings of over 80C on the road and at the White mark on the gauge in the shop.

If the thermostat is operating normally and there's no coolant loss, you may have a gauge or sender lying to you.

If possible, stop by someone with a RAYTEK infra red temp' gun and check the rad' and stat housing....you may find the temperatures lower than indicated.

BTW....has this happened lately ?

If this has always been the case, the old coolant pump may have gouged out the front of the block and have increased clearence between the impeller and block face.

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Jkoch · #4 05-07-2007, 11:10 PM

thanks for the input. Changed my coolant cap today also. It reads 20lbs, is this correct for this car?

I'm not sure I discribed the clutch fan well earlier. When the car is hot I can give it a spin (like wheel of fortune) with one hand and it travel about 1/2 turn. Does not seem to have much resistance. By the way ,the resistance on the clutch fan is the same whether it is cold or hot.
I may be able to get my hands on an infrared gun.

Previous owner unhooked the AC so the aux fan does not run. I put 12 vdc to it today during idle and the temp creeped up to the red zone anyway.

Could the radiator be bad?
Could it be possible it is the head gasket? I am not losing coolant that I can tell and the oil still looks good?

What would the tail pipe like like if the head gasket was the issue?

Also, As a side note my idle is also an issue as I believe the idle valve is bad. Would this have anything to do with the heating issue?

thanks for you help again!

Tomguy · #5 05-08-2007, 12:40 AM

I doubt it's the head gasket. The m116 and m117 engines almost never experience head or head gasket failures if they weren't overheated. In order, I'd check/perform:
1) TIMING
2) Sender gauge accuracy
3) Coolant level and air in the lines
4) Coolant flow (water pump bad?)
5) THOROUGH block and rad flush and replacement with water, then drain again and replace with coolant.

If your timing is off your engine can run pretty damn hot.
Edit: To clarify, that's ignition AND cam timing. The m116 and m117 engines have a "weak point" in their plastic timing guide rails. If they snap, your cam timing will be off. If you're lucky, you'll experience poor running or problems like high temps. If you're not, you'll have engine failure.

david s poole · #6 05-08-2007, 11:47 AM

replace fan clutch.it sounds like your prob.have some one else raise rpm's while you stand beside engine with hood up.if fan clutch is good you will feel,and hear a dramatic rise in amount of air being moved by fan as revs rise.