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  #1  
Old 04-02-2004, 09:46 AM
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Overheated M104 Part 2>

The evidence is strong that my wife's 1994 wagon overheated, causing the presence of antifreeze in #1 cylinder and loss of compression in #2 and #3 cylinders (25 psi). The mechanic states this can happen when the heat causes loss of oil from the cylinders (Mobil 1 10w-30, for those of you curious). He thinks it is very unlikely that the head is usable at all, and the wiring harness is toast. However, the pistons still move freely - the motor is not seized. He thinks the block "may" be OK. I have therefore purchased a used engine with 50k miles on it for $1000 (I could not find just a used head). I also have an unknown a/c leak - given my recent luck this may be the evaporator (or I could get lucky for once and have a bad compressor - HA!). My choices are:[list=1][*]Replace my entire engine with the used one as is[*]Remove the head from the used one and put it on my block[*]Put a new head gasket on the used engine, then install it as per #1[/list=1]
My wife wants to keep the car, even though it is a money pit. Before I let her do that I will find out about the a/c leak. My questions are:
  • How many hours should it take to remove the head from the used engine which will be delivered today?
  • Given the evidence, what are the chances that my lower end is OK?
Sorry for the long post, but I have NEVER faced such an expensive repair before and feel I need all the advice I can get!

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  #2  
Old 04-02-2004, 10:02 AM
LarryBible
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I'm very impressed with the XRay vision of your tech. How can he possibly know about the head without removing it and inspecting?

There are several things that could be wrong with the head, but all of them can be repaired by a competent machine shop. Most likely it is not straight or it has corrosion between water jacket and combustion chamber. A good machinist can weld up the latter and straighten the former.

The same concept carries over to the a/c problem. Don't diagnose until you have investigated. If there is a little charge in the a/c, charge it up with UV dye and then look for the leak. There are many sources of problems and leaks besides the evaporator. You can't just assume that the evaporator is the problem without diagnosis.

Would you go to a doctor that prescribes medicine without first examining you? I hope not. In the case of engine problems such as this there is no way to know until you take it apart.

If your engine was running good and not using oil before this happened, I personally would prefer doing headwork on that engine than to roll the dice with a used engine of unknown condition.

My $0.02,
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  #3  
Old 04-02-2004, 10:31 AM
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I hear you on the a/c>

and of course will diagnose before doing anything. The head is a different matter - a couple of mechanics have stated that the head may not be repairable if it is warped very much, because you can only remove a small amount of metal from it. Mercedes did not allow for more than 15-20 thousandths correction, according to them. But if your experience is different then WOW! The car did not use a drop of oil prior to this and ran fine. The failure, when it occured, was so "undramatic" that my wife did not even notice. You still think I should just tell them to remove the head and get on with it, eh? I can always return the used motor.
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Old 04-02-2004, 11:15 AM
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I'm not sure of tolerances, but I've perused countless threads over several years on this forum about W124 head gasket failures that were more dramatic than yours and how heads had to be reconditioned afterwards.

None I read had issues with the head after repairs...and I'm sure mine will blow eventually.

I agree with Larry (as i usually do ). Until the head is pulled and inspected, I wouldn't consider it DOA just yet. The warpage that may have occurred depends on the duration that the head was exposed to the overheat condition...

..Save your money on the used motor...the head gasket repair and head reconditioning is already expensive enough!
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  #5  
Old 04-02-2004, 12:37 PM
LarryBible
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Milling the head to straighten is not the only option available to the capable head repair shop. They can actually bend it and then anneal it in an oven.

The trick is finding a competent shop to do this. I know one that can if you can't find anyone locally and want to ship it.

Good luck,
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  #6  
Old 04-02-2004, 12:42 PM
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Thank you very much >

The head is coming off!
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Old 04-02-2004, 01:40 PM
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Chip, you didn't mention the mileage on the overheated engine. If you know the service history of the 50,000 mile used engine that may be the better choice. Need more details before recommending the best option for you to pursue.
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Old 04-13-2004, 02:23 AM
Spencer 300E
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I've been searching for a typical post invoving a overheating problem. Could you please relate the symptoms that you experienced with overheating involving head warping. My wife recently overheated my car and I'm experiencining some warm running condions...
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Old 04-13-2004, 04:00 AM
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Were me I would put the 50K engine in and then tear down and repair your present engine at your liesure (if it's really cooked save it for parts ). if it got hot enough to warp that much you might have taken the temper out of the rings.........

William Rogers...........
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  #10  
Old 04-13-2004, 11:26 AM
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Surprise, surprise - Larry was right!

and others who suggested the head repair route was viable. It turned out that the head was NOT EVEN WARPED! The head gasket failure was massive (worst head gasket I have ever seen, according to the tech) but the head was still straight. We did have a machine shop mill the bottom of the head because of corrosion, but it is otherwise just fine. We also had to replace the wiring harness (fine by me - the old one was garbage) and I still think the water pump was the original cause of the loss of coolant. Is there a good way to tell if the water pump is bad while the head is still out?

To answer your question, my wife never noticed any problem until she went out to start the car and it would not start (due presumably to the glycol in #1 cylinder). She did notice for the 5 miles drive home just prior that the engine seemed to have little power. The temperature gauge may have failed due to the wiring harness. I was seeing problems with the fuel gauge that certainly looked like intermittent ciruit problems just the day before. It had lost about 3 liters of coolant the day before and I refilled it, but the leak must have been really fast.

THANK YOU EVERYONE! THIS BOARD SAVED ME BIG $$$$!
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  #11  
Old 04-13-2004, 11:56 AM
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Re: Surprise, surprise - Larry was right!

Quote:
Originally posted by ChipJ
I still think the water pump was the original cause of the loss of coolant. Is there a good way to tell if the water pump is bad while the head is still out?
The water pumps on every car that I ever owned (including my W124, which lost the water pump several years ago), begin to leak. Most water pumps have "weep holes" that start to leak when the seals go bad.

On the W124, the failure was dramatic...fine one day, coolant all over the garage floor the next.

Cooling system issues began to bring themselves to attention around 100K...water pump, radiator neck, expansion tank, cap, thermostat, etc.

Now that you are getting your new gasket, keep an eye out for the rest of the components...the overheating may just have been enough stress to cause other cooling components to compromise themselves...
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  #12  
Old 04-13-2004, 12:00 PM
LarryBible
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So, as I suspected, your techs X-Ray vision wasn't all that he cracked it up to be.

You just can't tell about these things until you open them up. You just never know what you're gonna find.

Good job,
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  #13  
Old 04-14-2004, 11:06 AM
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Re: Overheated M104 Part 2>

Quote:
Originally posted by ChipJ
[B............ even though it is a money pit.
Sorry for the long post, but I have NEVER faced such an expensive repair before and feel I need all the advice I can get! [/B]
LOL, an honest Mercedes owner..... sorry to hear about your problem with what people on here call, "bulletproof"

ChipJ so how much did the little incident debit you by? head gasket and wiring harness...
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  #14  
Old 04-14-2004, 02:31 PM
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Cost of Repairs

Head gasket alone is $1500 at this place. The head had to be machined along the bottom which added $300 (includes valve work as well), extra labor beyond just head gasket added $500, and the wiring harness replacement part was $600. The water pump WAS bad (along with the coolant temp sensor - explains why wife swore it never overheated!) which adds the cost of those parts to the bill. All in all, a new record for me of over $3000, tempered only by the realization that it could have been MUCH worse!

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