Very slight head gasket leak Mercedes 420 SEL?

Question

A couple months ago I bought a 1989 Mercedes 420 SEL that was very clean and obviously well cared for with service records. However, there is a very faint leak in the head gasket that is barely detectable. Compression and leak down tests reveal no problems. Took to two mechanics. One wanted $4000 to fix it and acted urgent about it. The other wanted $2800 and says not hurting anything--just check oil and antifreeze and keep eye on gauges. How serious is this problem. No antifreeze or water in oil or other problems and performs very well. How long can I continue driving it? Are Mercedes head gaskets known for minor leaks that are no big deal? I can afford to fix but would rather not if it is not a serious problem.

The leak was detected only visually by a BMW specialist. He did not conduct any leakdown test or compression test. He later indicated it wasn't an imminent emergency. I took it next to the German Engine people in town who said it was not an imminent emergency but that it will get worse, could be next month or could be five years from now. The compression was remarkable and everything in excellent condition. I live in a very mild driving climate near Seattle. I drive about 4000 miles a year. I just bought this car after someone ran into and totaled my 1987 Volvo GLE w/212,000 miles on it. (Had that for 15 years and very reliable.)

By the way, body is in excellent condition, graphite metallic with beautiful blond palomino leather hide of the finest quality, interior is immaculate. This is the most substantial car I have ever driven, probably even more so than my parents' 75 Cadillac Eldorado when I was a kid.

It is leaking oil, not antifreeze. It is in the back over the exhaust. After he cleaned it up he could only detect a very faint leak. There was also a leaking valve cover gasket that I got fixed.

I then had the German engine people do a full detailed inspection of the car and everything looks fine except a transmission box leak and this oil leak.

It had 167,000 mi when I bought it and now has 168,500 miles.

I want to thank everyone for your good answers. Collectively, they all help me determine my plan. I can't pick a best answer since there are a few that would qualify.

Answer 1

Are you SURE this is a head gasket leak???? I mean, really, all you say is that it's a very faint leak and barely detectable. Head gaskets don't normally blow like that. And the fact that there is no loss of compression and no leak down evidence suggests to me that this is not your problem. Before spending a huge amount of money, I suggest you take it too a mechanic. Don't diagnose the car yourself. Say nothing. Just give him the symptoms. I think your self diagnosis is very likely WRONG.

Answer 2

Bill, I don't know if this is a common problem or not with Mercedes but my theory is that any leak is a bad leak. Under "normal" conditions it may last another ten years but you can't control the weather. You can bet money that this problem will get worse with time. In extreme heat or under servere driving conditions the pressure from the hot coolant in your system could blow the gasket while you drive or right after you stop. In extreme cold, the water in the coolant could freeze in the crack and force the gasket apart. I have had both of these happen to me in the past. I would recommend that if you have the funds and plan to keep the vehicle for any amount of time that you go ahead and have it repaired. It sounds like you have a bit of time so use it to shop around to find a reputable mechanic that won't take you to the cleaners.

Answer 3

Mercedes Head Gasket

Answer 4

Rog on the last two answers. Where is the leak and how did you find it? Is it leaking oil or coolant?

After reading your additional remarks, I wouldn't worry about it, just keep it wiped off. The combustion ring on the gasket is still in tact, so let it go until other problems arise. If it starts to overheat at all, I would say it's time to get it fixed.

Answer 5

It's not an emergency as long as it doesn't fail catastrophically (but eventually it will). What you don't want is for it to blow out and dump coolant into your cylinders. And you don't want to get stranded somewhere. And you DON'T want everybody to see your beautiful Benz sitting along side the road leaking coolant all over your shoes.
Drive it and watch it for now but I would plan on getting it fixed by the second mechanic reasonably soon. Check around for other shops in the meantime.
Congratulations by the way, SEL's are awesome cars! I'd love to get my hands on a 560 SEL! Ahhhhhhh, Mercedes Benz.

Answer 6

I agree with Mr. Z, but if you have taken it to several shops and they truly have looked at it and found the same thing, then OK, I'll bite. You can buy thinner cold oil and it may help to reduce oil pressure and slow the leak. Maybe 5W30. Also, you can retorque the head. That may help seal it, but I am skeptical. Once oil has found a path, then it will usually always have a path. But, it's worth a try. Good luck.

Answer 7

First of all, I want to know, how was this slight leak was detected? or you just assuming, that you have one..do you keep having to add coolant and see no visable signs, and this is a good guess..I am kinda curious..did you have valve covers removed and valves loosened and spark plugs removed and cylinders pressurized, and air comes out from the valves or one of the cylinders on either side..were you shown this small leak..please let me [e-mail]

Answer 8

get it fixed, it may be nothing now, but that is a huge problem. the $2800 seems pretty fair (the reason he's not being very urgent about it is because he wants it to become a big problem so he can charge you $4000 to fix it like the other guy) anyways it is urgent

Answer 9

Go to your local parts house, I believe there are something that you can buy that would seal it. You be able to pour into Radiator or something to pour in to oil.