300E advice Benzmac? - PeachParts Mercedes-Benz Forum

kfuller · #1 08-08-2002, 09:30 PM

Benzmac, after driving for about 10 min. I lose about a quart of coolant. As best as I can tell, the leak appears to be at the rear passenger corner of the engine at approx the same spot that I've had a minor oil leak for quite some time. Coolant leaks from this area until the engine has cooled down for 45 min or so. I looked around for another source but it looks like the head gasket to me. Searching other posts about head gasket problems doesn't reveal any similar problems with head gaskets though. Is this likely?

If this is the head gasket, is there any other work that is suggested? Such as a water pump maybe as this has not yet been replaced. Should the head be reworked?

1990 300E 160K

Ken

#2 08-08-2002, 10:19 PM

I would strongly suggest removal of the cyl. head to check the flatness of the head, because the right rear cyl. area is a common area for oil and coolant leak on theat engine. At that time, it may not be a bad idea to check the back sides of the valves for any excessive carbon/oil buildup. Also, the replacement of the water pump would be another idea at that time whilr the head is off.

Paul R. 21 year MB tech.
MB master and ASB tech

Michael · #3 08-09-2002, 08:11 AM

Ken/All,

It really sounds like it's time, as stated by Paul R. (and Welcome Paul-nice to see another pro out here

) Did it all on my '88 'TE last year (same motor as your car).

Since your car left the factory, the valve guides have been improved 3-4 times, increasing longevity/durability. And by virtue of an M103's valvetrain design, they do work the valve guides hard. The valve seals are better, too, and yours are 12 year old rubber at this point.

The only other thing I'd recommend is changing your coolant hoses-the thing's apart and your cooling system is open, so bite the bullet and they are one less thing to worry about for the naxt 150k or so

Best of luck, and enjoy the renewed car (watch-it'll even shift better)

kfuller · #4 08-09-2002, 09:11 AM

Thanks Michael.

So,
1) get the head done,
2) and a new water pump.

What about the timing chain guide. A couple of posts indicated that these are falling apart at this millage.

Also, with this car isn't this where the typical "timing cover oil leak" would be fixed?

Ken

kfuller · #5 08-09-2002, 09:21 AM

Thanks Paul. One question though: at 160K wouldn't a head always be sent out to be cleaned, checked, trued, valves lapped, new seals, etc? Rather than just new seals. I mean, wouldn't you expect to see a carbon buildup at the valve seats and wouldn't this require a machine shop?

Ken

#6 08-09-2002, 09:57 AM

You'll need to do the seal anyway when taking the head off and then reassembling.

Joel

marinmbfan · #7 08-09-2002, 05:07 PM

Using the (odd) terminology from the factory service manual, the cover you must remove and reseal when doing the head is the "top cover", the one in front of the camshaft. The "timing cover" is farther down the front of the engine, and requires a whole bunch of extra stuff be stripped off the front of the engine to get to it and remove it (remove radiator, fan bearing bracket, crankshaft pulley, alternator, and a bunch more). It definitely isn't part of a normal cylinder head R&R on a 103. I know because I was in the process of a normal cylinder head R&R when I accidentally busted a timing chain guide rail and had to take the whole detour to pull the timing cover to fix that. As far as whether its "top cover" or "timing cover" leaks the 103's are notorious for, I couldn't tell you. Mine both "seeped" a tiny bit before I had to do my timing cover, and they still "seep" a little bit now.

#8 08-10-2002, 08:13 AM

Correct, meant to say top cover. From what I've read and seen on my car it's the top cover that's notorious for leaking. Replacing mine this weekend. Having trouble finding the locktite 5900.
Joel

stevebfl · #9 08-10-2002, 08:47 AM

You guys sure love to spend money. I almost never see coolant leaks from 103 head gaskets. It is way more likely that you have the heater hose o-ring leaking. A hose could be leaking also but they usually aren't that affected by temp; although pressure increases all leaks.

Find the leak, don't just start spending money. I sure would like to be the one doing all the wasted head jobs on this board.

kfuller · #10 08-10-2002, 07:31 PM

Believe me Steve, I certainly don't relish the thought of getting the head done (regardless of that pesky oil leak that I've had for a while).

I'm going to look at the leak a little closer in the morning when I have some time. I would like to find you correct.

By the way though, aren't you referring to the heater return line? Because if so, it's on the front of the engine, driver side. My coolant leak appears to be at the rear of the engine, passenger side. Is there another heater hose with an o-ring that I'm overlooking maybe?

Ken

kfuller · #11 08-11-2002, 11:19 AM

Well I jacked it up and took a look this morning. The leak appears to be about 2-3 inches from the rear of the block at the junction of the block and head (on the passenger side as mentioned earlier and almost the exact location where I have a slow oil leak) -- looks like the head gasket for sure but if anyone knows of another source, please speak up.

Now the hard part -- finding an independent with experience on 300E's that I can trust. Anyone know of one in my area because I trust absolutely no one???

I have the sinking feeling that I'm going to have to go to the local MB dealer for this.....

Ken

Benzmac · #12 08-11-2002, 12:53 PM

As Steve said, I never see coolant leak from this area. I see it more often from the o-ring that is sealing the heater pipe (near the oil filter) to the head. The thing will leak there and run down the head where it drips off.

Good luck. I think a $2.00 o-ring and a hour labor will fix the problem.

kfuller · #13 08-12-2002, 07:21 AM

Thanks for the advice Benzmac. I'll look some more and see if I can find that heater hose. Geez I hope that's it...

Ken