E300 DT overheating after episode of high revs - PeachParts Mercedes-Benz Forum

dtf · #1 02-16-2007, 10:20 AM

Hello - the wife got the '99 E300 Turbodiesel stuck between two big trees - on ice - in the driveway going uphill

. I worked the car for 45 minutes, really hard rocking and trying to drive it out of the nasty spot. Then I look down and see 120C on the gauge and shut the car down and pop the hood to cool it off. The fans were not cooling the engine even though they were going full blast. This morning it started fine but wifey calls and says the thing is over heating again on the highway. I go out and swap the truck for her car, send her off to work and call AAA for the tow. The oil level is fine and not contaminated - the coolant level is fine and still nice, clear and yellow - I'm thinking I burnt out the water pump with those high RPMs in freeing the car from the ice

?

whunter · #2 02-17-2007, 01:33 AM

The water pump is possible.

Please check the serpentine belt tensioner.

If the belt is slack = slipping on the pump = overheat = a very cheap fix.

Have a great day.

dtf · #3 02-17-2007, 09:23 AM

The shop called yesterday and said early diagnostics suggest a closed thermostat. I thought MB thermostats were designed to fail in the open position? Doesn't make sense but they said as the car warmed up in the shop the lower hose was cold where as the upper hose was hot.

Is the belt tensioner you speak of the same as the belt tensioner shock? If so that was replaced about 30,000 miles ago. I will ask them to check that too. The car didn't sound the same yesterday morning when it started but it was very cold outside.

Matt L · #4 02-17-2007, 11:14 AM

I didn't think M-B thermostats were anything special. All thermostats will usually fail in the open position, since they usually fail by getting cracks in the wax. Occasionally they fail in the closed position.

But always test the old one once you remove it, to ensure that it really is the problem. Not that you should put the old one back in, but you need to know if you must keep looking for other faults.

engatwork · #5 02-17-2007, 01:33 PM

Quote:

keep looking for other faults

Have ya'll looked at the lower section of the radiator or cooling system? Make sure nothing got up in there during the ordeal.

I have seen a plugged radiator do the same thing you are experiencing but that happens more gradually over time.

uberwgn · #6 02-18-2007, 07:49 AM

Could the visco fan be an issue??

engatwork · #7 02-18-2007, 08:18 AM

Quote:

over heating again on the highway

Not if it is just overheating on the highway. If overheating in traffic then that could be an issue with the fan clutch.

Parrot of Doom · #8 02-18-2007, 09:08 AM

Is it actually overheating?

Could be a dicky temperature sender.

TMAllison · #9 02-18-2007, 12:44 PM

Quote:

Originally Posted by uberwgn

Could the visco fan be an issue??

At 120c the fan clutch should be engaged and howling.

I'd check it first as its easiest.

Can its oil fill get so thick in extreme cold it wont engage?

nhdoc · #10 02-19-2007, 08:23 AM

My money is on the thermostat. I have had as many of them fail closed as open over the years. It's a cheap and easy fix to try so why not at least do it and see if that was all it was. Worst comes to worst you'll have a new one in there as preventative maintenance, but I would bet that will fix the problem. If it is not that then I would be looking at the water pump next.

If the hose is cold then it is NOT the fan clutch, it is a coolant circulation problem. The only 2 things I know of that can cause it are either a failed thermostat or failed water pump. The original water pumps were known to have the plastic impellers break and fail to turn so this is not unheard of at all.

dtf · #11 02-19-2007, 12:25 PM

Got the verdict from the shop. They replaced the thermo stat and it drove nice around town but on the highway it cranked up to 120C again. They said on these engines (OM606) a small head gasket problem will leak into the combustion chamber and be blown out the exhaust. They think the high temp fried the thermo too.

I had to add a coolant the following morning and couldn't find where the coolant went to so maybe their theory is right? Sounds logical?

Targa-NF · #12 02-19-2007, 01:03 PM

I had the same thing happen to my 81 300SD. The thermostat failed in closed position. I just replaced it and away I went. Cheep and easy fix. Jay

thorsen · #13 02-19-2007, 02:08 PM

Quote:

Originally Posted by dtf

they said as the car warmed up in the shop the lower hose was cold where as the upper hose was hot.

If the upper hose is hot, then the thermostat is opening.
If the lower hose is cold, the radiator works extremely well or is obstructed internally.

dtf · #14 02-20-2007, 07:10 PM

The verdict: Blown head gasket plus pits in the head where the piston wall meets the block. Estimate for the entire job including the machining of the head ~$2500.

Good thing the car is paid for...not the most reliable car I've ever owned. The '94 wagon makes this car look sick as far as reliability goes...and my wife wants to get rid of the wagon...never!...although it will need blower regulator and blower motor soon and maybe the dreaded evaporator soon too...

Good thing i have the Tundra

aklim · #15 02-20-2007, 07:51 PM

Quote:

Originally Posted by dtf

The verdict: Blown head gasket plus pits in the head where the piston wall meets the block. Estimate for the entire job including the machining of the head ~$2500.

Good thing the car is paid for...not the most reliable car I've ever owned.

Rocking it back and forth means no air flow while revving the engine. That could have caused the head gasket to fail. Not sure how you feel that this car is not reliable. I wouldn't have gone rocking for 45 mins. I'd have gotten a tow or something. If I had to do it, I wouldn't do it for more than 10 mins and would have watched the temp gauge all the while.