overheated/won't start/ bad head? - PeachParts Mercedes-Benz Forum

Lee C · #1 10-02-2007, 03:51 PM

My 87 300td overheated and now it won't start. How do I know if I've melted the head

The engine turns over but won't start.

barry123400 · #2 10-02-2007, 04:31 PM

Best do a compression check to make sure you have not taken the temper out of the rings. Good ideal anyways. If the head is damaged it might indicate where. Much depends on how hot the engine got. Even if the head cracked it should normally partially run.
Describe how hot it was and for how long it was operated. That way more sensible guesses can be given. Did it boil all the coolant out? Was the engine so hot it smoked or produced a smell? Did you shut down the engine or did it tighten up and quit itself?

dieseldiehard · #3 10-02-2007, 04:47 PM

Count on $pending $ome Dollar$
Sorry to hear about the loss. it will probably need to be torn down for sure, to check the head for flatness and cracks.

Lee C · #4 10-02-2007, 04:52 PM

The guage never went into the red zone, but almost. I turned off the a/c and by the time I got home it had cooled off pretty much. It didn't loose any coolant and never smelled. It only stayed hot for about five minutes. But today is the first time it wouldn't start.

TMAllison · #5 10-02-2007, 05:54 PM

Quote:

Originally Posted by leenkel@embarqm

But today is the first time it wouldn't start.

It seems you've been driving it since. How long ago did it overheat?

Lee C · #6 10-03-2007, 09:25 AM

As I drove it home it started to cool off after I turned the a/c off. Then the very next day it wouldn't start.

vstech · #7 10-03-2007, 12:24 PM

your coolant level never dropped? it never made it into the red zone... are you sure you have fuel in the car? can you test your glow plugs, it's probably not cold enough in FL yet to need glow plugs, at least not by the end of the day for sure, unless you have some compression issues. what fuel do you run? can you make a bypass tank and bleed the system and verify you are getting fuel to the injectors?

barry123400 · #8 10-03-2007, 08:16 PM

You did not really overheat the engine as such. You just where at the top operating temperatures. Some heads can be affected by this apparently on occasion. Right now I would do a general troubleshoot as the no start may not be caused by your moderate high average temperature event . Say the head developed a crack for instance at the time. The car would still start the next day.
To check head remember the hard radiator hose test if your coolant system is tight. You can look for bubbles in the coolant when cranking too. The main point is that your no start may or may not be related to that event. Most likely not though. The starter does turn over the engine? If the engine does crank normally first check is the glow plug function. Some will just not start without it. Coincidences do happen in life. Glad to hear you did not cook your engine. That does happen and can be really bad.

Gauge · #9 10-04-2007, 01:22 PM

This is why I never like mixing metals, as in, an engine with a cast iron block and an aluminum head. They expand and contract at different rates and if the temperature difference is high, the head gasket just can't seal the 2 metals together.

This is why I prefer the older benz's with the cast iron blocks AND cast iron heads. Overheating these engines never seems to do any damage.

Lee C · #10 10-11-2007, 05:19 PM

Towed the White Whale to a garage in Destin where they thought the glow plug relay switch was bad. Switched it out but it didn't help. Managed to start engine by holding the emergency stop handle all of the way to the top,12 o'clock, while cranking. Drove to another garage in Fort Walton Beach that works on Diesels where Moby Dick was the only car there. Suspicion was that the I.P. was the problem. Several leaking hoses were replaced, ditto for a very old,dirty, small fuel filter that I didn't even know about. Compression checked at 210 for all 6 cylinders. I.P. seems to be O.K. but engine still looses prime.???

rrgrassi · #11 10-11-2007, 05:37 PM

That 210 on compression seems low, but at least it's even.

Lee C · #12 10-18-2007, 04:12 PM

Thanks to all, the White Whale lives. Barry123400 was spot on. Coincidences do happen. VSTEC pegged it recommending that we check on the fuel.
What happened was this. The piston in the lift pump was stuck and fuel was backing past the check valve and loosing prime. New pump, filters, several lines and O rings and Mobydick was back on the road with 221,000 and counting!
Thanks again and Happy Motoring

bustedbenz · #13 10-19-2007, 10:49 AM

Maybe not a coincidence. If you had a fuel delivery problem, that ultimately resulted in your engine refusing to start due to not receiving fuel... let's just suppose, as a what-if theory, that the system started failing about the time your temperature started to climb.

Could this failure result, not only in the fuel system losing prime after shut down, but also in refusing to deliver quite enough fuel to the engine while it was running that last time during the overheat...

At the time the temp started to climb, as the fuel system failed, or at least lost some efficiency... the fuel/air mixture that the cylinders were burning became leaner, more air than the ideal mixture and less fuel.

A lean engine runs hotter than a perfectly tuned or even slightly rich one... because the greater air:fuel ratio means it has the chance to burn hotter. Nobody's quite sure why... maybe a slight fuel excess has a cooling effect up to a point, maybe air just burns hotter than fuel anyway, and so more of it means more temps... but it's a fairly accepted theory that a lean engine runs hotter than a perfect mixture. So.. how likely is this?

2.5Turbo · #14 10-19-2007, 03:03 PM

I don't think that would be the case in a diesel engine. That would happen in a gasser, but not a diesel. Diesels run on an excess of air. When all the excess has been used by the fuel, you get black smoke. You can dump all the air you want into the cylinders and it won't do anything unless you add more fuel. How come those who crank up their turbo boost without adjusting the full load in the IP don't overheat all the time? They may be increasing the EGT's, but that's only due to the fact that the turbo is increasing the intake air temps because of the higher pressure, not because of a leaner burn.

Lee C · #15 10-19-2007, 04:42 PM

Sorry, I forgot to mention that the high temp was caused by a blown fuse on the a/c aux fan. I had by-passed a faulty switch and wired the fan to stay on using a 15 amp fuse which I have since replaced with a 20 amp one that seems to be working better.

What I'm wondering about is why this piston got stuck? Curious that it happened less than 2000 miles after I started using ULSD. Did someone not put in enough additive to bring the lubricity up to spec? Or was it just a coincidence of old age. Maybe I should start using a fuel additive myself since I'm over 200,000