91 300E M103 Overheated - Blown Head Gasket? - PeachParts Mercedes-Benz Forum

gmercoleza · #1 08-13-2006, 09:11 AM

149,000 miles. It's me to blame - I think what happened is I let the coolant run low. In taking a closer look, the coolant level sensor appears to be corroded so I never got a warning.

While cruising along, the A/C suddenly shut off. Confused, I stopped and restarted the engine but the A/C still wouldn't blow cold. At that moment I noticed the water temp gauge was buried way past 120. I couldn't believe my eyes. I pulled over and turned the engine off but it was too late - steam was coming out from under the hood.

I popped the hood and saw exactly what I thought I would see - steam bubbling all the way around the engine from the seam where the head meets the block.

The car is in the parking lot of a business that doesn't open until Monday. I had my wife pick me up and we just left it there overnight to cool off. The car is only about 10 minutes away and I am going to bring some water to fill up the system and start it up, hopefully drive it home before traffic picks up this morning.

After the gasket blew, I did start the car to move it to the parking lot. When I did, it still idled perfectly and appeared to run fine. Is it possible that everything will be back to normal after cooling off? Can I just change the coolant and the oil and try driving the car? I don't expect this to be easy, in fact I'm already pricing a rebuilt head, new gasket, and stretch bolts because I figure I'm going to need them.

Anyone have experience with this type of situation?

engatwork · #2 08-13-2006, 09:17 AM

Quote:

Is it possible that everything will be back to normal after cooling off?

If you did not damage the head you should go out and purchase a lottery ticket right now. The loss of coolant was your warning but because of the switch being inoperative you did not realize it in time. Put coolant in and run it to see what happens. If it runs hot then you will probably need to pull the head.

Rahulio1989300E · #3 08-13-2006, 05:09 PM

NNNOOOOOOOOOOOOOOOOOOOOOOO!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

What did that M103 ever do to you?!?!?!?!?!

Good luck!

Gilly · #4 08-13-2006, 05:16 PM

Probably aren't going to need the head bolts. Don't think I've ever found them stretched enough to require new ones, so you can save that money anyways. i wouldn't make the jump to a new/rebuilt head until you or a machinist has had a chance to check it for flatness.
Gilly

gmercoleza · #5 08-13-2006, 09:19 PM

I checked the oil before cranking. It wasn't foamy and had no indication of coolant in it. I poured nearly 2 gallons of antifreeze mixture in and started it up. It idled very nicely and I immediately put it in gear and told my wife to follow behind me. Drove it like a bat out of hell, and got it home within 20 minutes. Got it up to 80 mph at one point. It never seemed underpowered and idled perfectly at each light, with the temp needle around 100. About 3 days ago I did the 1/4 turn clockwise on the EHA to solve a stumble and smooth out the idle. Driving it today the idle and off-idle acceleration were still silky smooth.

Got it home and pulled the plugs, then ran compression. Here are the results:

1 - 140
2 - 145
3 - 145
4 - 140
5 - 145
6 - 140

I found a very small tear in the Y-shaped heater hose that plugs onto the head. This must be where the coolant slowly escaped, probably allowing airlock which prevented the coolant from circulating. Removed and took the hose to O'Reilly - they didn't sell the exact hose but did sell me one that was a close diameter with a 90 degree bend in it, along with a plastic splicer and 2 hose clamps, all for $3.95 tax included. Cut off and fabricated a new elbow end, and reinstalled the hose. Filled back up with coolant and let idle in the driveway with the A/C on for about 45 minutes and the temp gauge never went above 110, which is normal behavior for this car when it's 100 degrees outside. While it idled, I crawled around the engine and examined every visible area looking for leaks or steam, and I never saw any. Drove back to O'Reilly to return the screwdriver the guy lent me, also gave him $10 and thanked him as he undoubtedly saved me a tow.

I am puzzled. I saw the temp gauge at 125 with my own two eyes. Including moving the car out of a turn lane and to a safe location, I probably drove the car in that condition for at least 3 or 4 minutes. I popped the hood and saw coolant bubbling out from the seam between the head and the block. Did I dodge a bullet? Should I cancel my life insurance policy tomorrow?

I will be ordering that y-shaped hose from FastLane shortly.

engatwork · #6 08-13-2006, 09:28 PM

Did you pick up that lottery ticket

?

softconsult · #7 08-14-2006, 08:40 AM

Those readings sound too high.

Are both your auxilliary fans working?

Steve

michaeld · #8 08-14-2006, 09:31 AM

gmercoleza,

The compression test could indicate a blown head gasket to someone who knows how to read the gauge. But there are two other ways that are better:
1) A block test, using a chemical that "sniffs out" exhaust gasses in your coolant.
2) A pressure test. The nice thing about the pressure test is it costs you nothing (you can get a pressure tester at Autozone on their loan-a-tool program). I would do the pressure test three ways:
a) Install the pressure tester to your expansion tank and pump to the pressure on your cap. Wait about five minutes and see if the pressure holds.

b) Start the car and let it get to operating temp, then connect the tester. You are looking to see if the pressure goes up (particularly above the psi of your system). The engine psi is a lot higher than the cooling system psi, so if there is a leak, your cooling system psi will spike.

c) Let the car cool down. Install the tester and then start the car. You are looking for fluctuations in the gauge. If you have a blown head gasket, the needle will fluctuate as the engine rotates to the cylinder that has the blow-out.

I would try to rule out a blown head gasket before spending a lot of money replacing what COULD be wrong, only to find out what you needed all along was a $3000 head gasket replacement.

michaeld · #9 08-14-2006, 09:36 AM

Quote:

Originally Posted by michaeld

gmercoleza,

The compression test could indicate a blown head gasket to someone who knows how to read the gauge. But there are two other ways that are better:
1) A block test, using a chemical that "sniffs out" exhaust gasses in your coolant.
2) A pressure test. The nice thing about the pressure test is it costs you nothing (you can get a pressure tester at Autozone on their loan-a-tool program). I would do the pressure test three ways:
a) Install the pressure tester to your expansion tank and pump to the pressure on your cap. Wait about five minutes and see if the pressure holds.

b) Start the car and let it get to operating temp, then connect the tester. You are looking to see if the pressure goes up (particularly above the psi of your system). The engine psi is a lot higher than the cooling system psi, so if there is a leak, your cooling system psi will spike.

c) Let the car cool down. Install the tester and then start the car. You are looking for fluctuations in the gauge. If you have a blown head gasket, the needle will fluctuate as the engine rotates to the cylinder that has the blow-out.

I would try to rule out a blown head gasket before spending a lot of money replacing what COULD be wrong, only to find out what you needed all along was a $3000 head gasket replacement.

Oops: I read through the thread too quickly, and saw that you don't seem to be overheating anymore (which you would still be doing w/ a bad head gasket). I'll leave the post up for posterity anyway, just in case someone needs to read about how to do a pressure test.

P.S. A more cynical person would say that you just USED UP your luck, and you'd better go right down and double that life insurance policy!!!

gmercoleza · #10 08-14-2006, 09:58 AM

Quote:

Originally Posted by softconsult

Those readings sound too high.

Are both your auxilliary fans working?

Steve

I agree, the compression seemed high to me. I expected 130 to 135 especially with 150,000 miles on the engine. Who knows, my gauge could need calibration. I think the more important thing is that the measurements are all within 3.5 percent of each other on a hot engine.

Both auxiliary fans are working. Actually, I couldn't resist temptation and drove the car in to work today, a 45 minute commute. Had it up to 80 mph on the tollway, no problems at all. Watched the temp gauge more than the road, I think. It never went above 105, got as low as 85 on the tollway. Idles smooth as silk at the stop lights. I really am puzzled. ???

softconsult · #11 08-14-2006, 10:40 AM

I've had three of these 124's. On all of them the needle sits at about one needle width over the 80 mark. That is true even when cruising in 100 plus degree weather. Idling in 100 degree weather, some increase , but never ever to 110.

Could be a lot of things, but sounds like there is a problem with your cooling system. Waterpump, thermostat, radiatior, or something.

Steve

gmercoleza · #12 08-14-2006, 02:04 PM

Water boils at 100 degrees, however the cooling system contains coolant, not water. Coolant's inherent properties, along with a pressurized system, raise the effective boiling point to 120 degrees. Anything below that is safe. My point is that the coolant temp on my car is behaving exactly as it always had, which is puzzling given that it clearly overheated.

softconsult · #13 08-14-2006, 02:31 PM

I was just trying to give you some data points that , logic point to your engine not operating similar to my experience and actually to the experiences I have picked up on other lists .

Your coolant does contain water. 50% Water / 50% Coolant. 60% Water and 40% coolant will cool more effectively. 50/50 + Water Wetter from Redline Products will cool slightly better.

When was the last time you replaced your thermostat? If it is not functioning correctly you can have restricted flow.

Hopefully, you are running either genuine MB Coolant or ZerexG05 which is the same thing. If not then you could have some corrosion problems going on . If your radiator is original , then at 150K it could be ready for a replacement. Here's something else. Overtime bugs and road junk get packed in behind the auxilliary fans and at the bottom of the heat exchanger.
This can also cause cooling system problems.

Steve

gmercoleza · #14 08-15-2006, 01:51 PM

I watched the needle again today as I ate lunch in my car. When idling in 102 degree heat, the needle hovers around 100. It goes just a hair above 100, then I hear the aux fan kick on, and the needle drops to just below 100 and stays there, with the aux fan running the whole time.

The radiator is free of bugs and is squeaky clean both inside and out. It is not the original radiator but was upgraded to the newer type with metal inserts. Either way, this experience has scared me to action. Among other things, I have ordered a new heater hose and thermostat from FastLane and will be installing them as a precaution. I will also flush everything and refill with the correct zerex coolant.

Gilly · #15 08-15-2006, 04:10 PM

Sounds like a stuck open thermostat. Yes OPEN not closed.
Gilly