Latest Mechanical Mayhem

speeder · speeder's Garage

I sold my 1996 Mercedes S500 to a friend about 6 months ago. It's been running hot and all of the normal causes have been addressed or ruled-out. It's a bit of a long story, but it blew a HG before I owned it and the repair was done by a shop whose work I do not have confidence in.

I have no idea what they might have done wrong, beyond guessing, so I thought I'd let you guys guess as well. The heads are coming off to see if they could have used the wrong HG set and blocked a water passage or (??) I have already previously removed the intake manifold and there was no apparent blockage with those gaskets. It is definitely a circulation problem and these components have either been replaced or ruled-out as causes:

-Radiator
-Water pump
-Thermostat
-Auxiliary fans
-Fan clutch

I should have a contest and give the winner some small prize if he or she guesses it before it's conclusively diagnosed.

Tearing it down:

Rick V · 06-24-2012, 01:53 AM

Do the guides and tensioners WYIT. They are prone to breakage for no reason.
As for running hot, I am going with getting combustion into the coolant system, bad or improperly installed headgasket, or a warped head,

Zeke · 06-24-2012, 07:08 AM

Do those cars need to be burped when refilling with coolant? If so, can an air pocket cause cavitation? JAT.

sammyg2 · 06-24-2012, 07:14 AM

That's why you don't sell anything to a friend.
it never stops being your problem.

Noah930 · Noah930's Garage

It ran fine while you owned it, but NOW it runs hot? Or it's been hot the whole time?

jsoderbe · 06-24-2012, 07:43 AM

Hi, my friend with an engine repair shop had an S600 where the cylinder sleeves sunk, creating what you are experiencing....

Very expensive and a lot if work. The engine had to be pulled, totally disassembled and machined, if I remember it right.

Regards,

Johan

speeder · speeder's Garage

Quote:

Originally Posted by Noah930

It ran fine while you owned it, but NOW it runs hot? Or it's been hot the whole time?

When I had it, it ran a little hot but nothing like this. I, and others more versed in Mercedes repair, thought that it was caused by something outside of the engine block and set out replacing all of the things listed above. There was an issue with the interior heater core(s) plumbing and it had been previously diagnosed as causing the circulation blockage, incorrectly IMO.

There is more to it, it's a long story. It was not overheating like this when I sold it but it had some symptoms. I should never have sold it w/o comprehensively solving the issue.

speeder · speeder's Garage

Quote:

Originally Posted by sammyg2

That's why you don't sell anything to a friend.
it never stops being your problem.

Generally good advice, for sure. In this case, even if I'd sold it to a stranger, I'd have to stand behind this problem because the writing was on the wall when I sold it. Unless it was expressly stated that it had a mechanical issue and was being sold as-is.

In this case, a good friend needed a car right away because his car was stolen and not recovered. A 1988 Targa of all things. I loaned him the S500 and he liked it so much that he wanted to buy it. I wanted to sell it as well, it was an extra car that fell into my life. I thought that it was a good car for him, (only 65k original miles at the time), and did not mind making a deal where I agreed to fix some things that I would have really had to fix anyways if I kept it.

Sometimes you get lucky with a hot running condition and it's just a bad radiator, etc. This time was not the case. There is a blockage somewhere and I'm about to find it.

A930Rocket · 06-24-2012, 09:54 AM

Improperly installed or wrong head gasket from earlier repair? Cracked block or head?

Superman · 06-24-2012, 10:41 AM

Seized muffler bearings.

crustychief · crustychief's Garage

My guess. Not getting all the oil / coolant out of the head bolt holes before installing ( new ) bolts.

edgemar · 06-28-2012, 05:46 AM

any update?

speeder · speeder's Garage

Yes. I'm going to pick up the heads this AM at the machine shop. There is nothing apparently wrong w/ them. They have been previously shaved but are still within spec, barely. Mercedes does not allow much in the way of cutting these heads.

Im ordering a new gasket set, (Victor Reinz), I'll have it in a couple hours. I need to flush-out the block really well and make sure that there is no blocked passages anywhere, then put it back together. I'll take some pictures and update this thread as I go.

edgemar · 07-02-2012, 07:49 PM

success?

aigel · aigel's Garage

Speeder,

What's making you think this will be any different after reassembly since you haven't found any blocked passages?

Before disassembly:
Did you test the coolant for combustion products?
Did you test the oil for coolant?
Did you pressure test the cooling system?
Results all clear?

It sounds to me as if there is a passage from the combustion chamber into the coolant - I am sure you had those heads checked for cracks, right? Do these blocks develop cracks? Sometimes a PO had a bad radiator or a leak and runs the car to overheat where it cracks. Then with a new radiator installed, it never comes back to normal.

I wish you luck. I'd probably buy out my pal and push that off a cliff by now ...

G

speeder · speeder's Garage

Quote:

Speeder,

What's making you think this will be any different after reassembly since you haven't found any blocked passages?

Before disassembly:

Did you test the coolant for combustion products?

Did you test the oil for coolant?

Did you pressure test the cooling system?

Results all clear?

It sounds to me as if there is a passage from the combustion chamber into the coolant - I am sure you had those heads checked for cracks, right? Do these blocks develop cracks? Sometimes a PO had a bad radiator or a leak and runs the car to overheat where it cracks. Then with a new radiator installed, it never comes back to normal.

I wish you luck. I'd probably buy out my pal and push that off a cliff by now ...

G

I'll update this when I have time, but it's none of the above. Just spent the entire day reasseming it.

Tobra · Tobra's Garage

Given what you have checked already, my guess is that you got some schmutz, RTV or something, down into a coolant passage so it won't flow right.

Superman · 07-04-2012, 06:17 AM

Did you check the muffler bearings like I suggested?

edgemar · 07-14-2012, 05:28 PM

speeder.....success?

Zeke · 07-14-2012, 09:16 PM

Quote:

Originally Posted by edgemar

speeder.....success?

Overheating issues can be some of the most ghostly of all diagnostics. IIRC, he got the car on the cheap because of the same issue. If so, others have gone before him and the problem did not get fixed.

If it didn't get fixed by the current efforts, some weird sch!t is going on like there's a penny stuck in a passage.

As I said, weird.

Restaurant workers will spit in your food and you can imagine a disgruntled mechanic sabotaging this motor at some point in the past.