300E overheating in traffic... Help
 

Hello Board, after solving my 300E's missing problem, I have developed another one. When I drive in regular traffic the temp is about 90 C. When I get into stop and go traffic, that is another story. My car reached to the point of where I had to pull to the side of the road and rev it up to 2000rpm and cool the car down. The temp hit the redline!! Well I have flushed the 2 year old radiator and I have a 50/50 coolant mixture, my thermostat is new. My outer fan kicks in, but does not do much. I have read a little about the fan clutch, but I spun it as hard as I could and it only went about 1/2 turn. It feels very stiff. I do not know if that means it is good or bad. I do not want to lose another engine due to an overheating problem. There is no trapped air in my system, and my expansion tank and cap are new. Does anyone have a suggestion on what my problem could be??

How stiff is the upper radiator hose when the engine's hot and running? Does it feel like there's pressure on the hose? If so, does the stiffness remain when you shut off the engine?

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

It would be worth the while to check the fan clutch. I have seen engine temps rising from this when all else seems fine.

Hi Mike690003,

I have a higher water content in my mix, like 60% water as that conducts heat away better than the antifreeze. I don't think you have to worry about -40F or something in Florida. You can also try to take a waterhose from behind and flush those dead insects out from the radiator.
I would let it idle and see how high it goes. Does the radiator get hot evenly, do you see/feel the coolant flowing through the reservoir? Do the aux. fans kick in and does the fan actually run faster when it is supposed to (107 C I believe).

The fan clutch seems like a good suspect,though, if it gets that high.

Good luck

Reinhard Kreutzer

Mike:

Your aux fan should run in high speed and blow like crazy -- if not, may be time for a new (or "recovered") one.

Test the fan clutch by listening at startup -- should make a roar that goes away in a couple seconds. It should also begin to roar when the clutch engages at about 100C, and move lots of air. If you shut the engine off when it's plenty hot, the fan should stop in less than a single rotation. If it spins much, the clutch is shot.

How old is your water pump?

Peter

It sounds like the engine driven fan is functioning properly. At about 100C the clutch should tighten and it will "roar" at about 2000 revs, but it cannot move enough air at idle speed.
Your electric fan(s) should engage high speed at about 105C and you should be able to hear it. You can run a test by idling the car with the hood open and observing electric fan operation. (Keep the A/C off.) If it does not engage high speed by about 110C then it's likely there's a problem either with the fan motor or the fan control circuit.

Duke

Well today I flushed the radiator, pressure washed the outside of dirt and bought the Prestone orange colored coolant. The coolant keeps the car a little cooler, but I stopped in traffic for a few minutes and the temperature started to climb. The aux fan hit full blast at about 105 C, but that did not help a lot. The temp hit 120 C and proceeded to hear redline. I pulled over and opened the hood. The engine fan was blowing, but not very powerful. The aux fan was going full force, is it time for a new fan clutch?? If so, how hard is it to replace??

Is your overflow tank's cap in good condition. I have heard that if it is not holding the pressure of the cooling system, then it could pose overheating problems.

Check the posts on refilling the fan clutch. Try Toyota and silicone as key words. It's not an exact science but it got my SE and SDL fans huffing and puffing again.

FWIW, I highly doubt a bad fan clutch is your problem. You have a bad thermostat or water pump or something.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

Sounds more like a rad clogged up or a pressurization problem, but the fan clutch is easy to replace.

It's not so easy to buy, though -- I think I paid $175 for mine!

One 8mm hex socket bolt in front, you need something to stick in the slot on the pulley bracket to hold the clutch so you can unscrew the bolt after unclipping the shroud. Three 5 or 6 mm (I think, don't remember) hex bolts holding the fan to the clutch.

Peter

Even when the thermo clutch tightens the engine driven fan doesn't flow much air at idle speed. That's why the electric fan is there. If you can hear fan roar at 2000 revs or above when the coolant temp first hits about 100C, the thermo-clutch is probably okay

Does this problem just occur at idle and low speed driving or does it also occur during high speed driving. If it occurs only at idle/low speed driving, the radiator is probably clogged and won't tranfer sufficient heat unless there is the much higher dynamic airflow from high speed driving.

The system should bleed air readily through the vent line from the thermostat cover/outlet to the supply tank, but it might take a two or three thermal cycles to purge all the air. Keep an eye on the coolant level. If it goes down with no sign of leakage, air may still be present. Top off the tank and watch for the level to stabilize with further cycles. When it does, the air should be purged.

It would also be a good idea to verify the temp gage reading by shooting the outlet with an IR gun to be sure it jibes with your temp gage.

The "orange Prestone" is Dexcool.

Duke

Is it my turn to be the fall guy? Ahem... Prestone does not sell a blend of coolant/antifreeze that meets MB standards <flame suit on>. I understand Zerex G05 meets MB standards as does the stuff you buy at an MB dealer. I have Zerex G05 in my Caravan (why won't MB sell the V-class here?) and it's colorless.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

Dexcool with its pure organic inhibitor package is as good, maybe better, than MB brand/Zerex G-05, which is a "hybrid" - basically an organic inhibitor package with a little bit of silicate.

The real bad actor in the antifreeze world is the traditional green stuff. It has an inorganic inhibitor package - lots of silicates and other salts. They provide good corrosion protection, but the salts precipitate out in the radiator tubes, so you have a nice corrosion free, but clogged radiator. Either way it's toast!

On a traditional brass radiator you can unsolder the tanks and "rod out" the deposits, but modern aluminum radiators are not usually serviceable.

Duke

There are a few places in miami,fl that I have called and they say that they service aluminum radiators. Well my radiator was replaced in 1999, so I will try them first and if that does not work I'll have to buy a new one.

BTW Does anyone know if I take it to a shop for a flush will that remove deposits out of the radiator??

The "radiator flush I bought at Autozone did absolutely nothing!

Are you using distilled water to fill the cooling system? If not, Miami city water is LOADED with salts, so you will have corrosion and plugging problems.

I don't think you will be able to get more than a reverse flush on an aluminum rad -- never seen one go back together and seal, they usually break off from fatigue. Better to get a new rad, flush well (nothing you buy over the counter is going to touch the crud in the rad), then fill with Xerex G-05 or MB coolant and distilled water.

Miami is hell on cooling systems.

Peter