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Discussion Starter #1
My 1995 S500 coupe seems to need a head gasket. Symptoms are that the car runs hot (~100-105C) and air is bubbling up through the coolant overflow tank. Diagnosis was by a local independent mechanic.

Indy mechanic estimated cost at ~$3500 to $4500 because head gasket implies valve job, and it's dumb not to do both sides. Is that solid reasoning?

I also called a local Mercedes dealer who told me over the phone that labor was 24 hours (book) @ their rate of $135, plus unknown amount for parts. They are willing to give a more complete estimate if I bring it in and pay for an hour of diagnosis labor, but it's sounding like they're going to wind up in roughly the same range as the independent mechanic.

The car is otherwise in good condition and has 103k miles on it (I've owned it since 86k). My math says it's worth doing the work versus junking it and having to buy something else. Thoughts? Is it worth an hour of labor to have the dealer take a second look? If their estimate is in line with independent, any reason to prefer one over the other?
 

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'84 300DT, '97 S320
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For a $ reference, in April/May this year, my independent shop charged $2600 for my S320 at about 208k mi, and they said this was probably the 2nd time. Probably a little high, but they did more than just the gasket replacement -- valve job, 8/1000ths shaved off, etc.

I once had an '84 Chevy Celebrity 4.3L V6 diesel (front-wheel drive), and eventually after 130k mi or so, its overflow tank started bubbling, and soot residue appeared. Both heads had gasket deterioration. After seeing that the front head had a leak, I knew with my luck the back head would have one too.

The 140 V8's usually don't have this problem. However, once an engine gets overheated (say it's not originally due to a bad gasket), then it's possible to have gasket problems.

So, yes, it makes perfect sense to do them both.

"Is it worth an hour of labor to have the dealer take a second look?" My first guess would be "no". It sounds like we already know it needs to have the heads off, so they'll see what they need to see when they do that anyway, and they won't know anything extra until they remove the heads. Some places include that investigative work in the final cost anyway.

If the costs are close, won't you get a free loaner from the dealer, but probably not from the independent?
 

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86 420SEL, 96 S320
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it is my experience that there is no reason to do a valve job when replacing a head gasket especially with only 103k on the clock. Just have the gaskets replaced and save yourself some cash.
 

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Discussion Starter #4
Thanks for the feedback everyone. I'm leaning toward having the independent do it, since they'll be the ones that I will continue to have doing other repairs and regular maintenance. I'll talk with them again about starting in just as far as the gaskets and then see if there's any valve/head work actually required.

Two more questions:

1) If they've got it open, should I have the timing chain replaced?

2) Due to winter ambient temperatures (even in SoCal), the car isn't running all that hot... would I be doing any long term damage if I drove it with the bad head gasket for several more months?
 

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86 420SEL, 96 S320
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Yes you could! I wouldn't continue driving it, by driving it you could be getting water in the cylinders and this could eat away at the piston causing serious damage to the engine. I've seen it happen many times.

As far as the timing chain, it wouldn't hurt to have it replaced. You're into it that far, it would be money well spent.
 
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