I need to change the head gasket, have a visible coolant leak under the exhaust manifold near cyl #5. Reading the pages in the Maint CD it is unclear if a special tool is required to access the head bolts. Also the text mentions to replace the bolts if stretched. What is the probablity of needing new bolts, or should I plan on replacing all on principle. Obviously I will inspect the head for cracks while I have it off, is there a common location that this head cracks? Thanks for the info

Assuming you have an M103 (what year 88-91 US spec 300SE), you don't need any special tools. You might not have the socket you need for the head bolts, a 12mm doube hex or something like that, but it's something many cars use these days. I got a a set of double hex bits from Pep Boys for ~$10 and it has the size of bits I need for the 300SE (12mm) and 300SDL (10mm). The bits fit into a 1/2" hex socket. About 2" of bit sticks out of the socket and that's enough. I see special tool catalogs with 6-8" of bit. Such tools might make a personal statement but I don't see how they'd be necessary in an M103.

As long as you can clean the bolts and they aren't stretched, you should be able to reuse them. My head bolts were 3mm shorter than allowable so I imagine they can stretch quite a bit and still be okay. I think the more relevant issue will be the condition of the threads. I'd replace the head bolts with corossion and/or pitting in the threads that can't be cleaned away. Don't forget to tap the block threads and clean the holes thoroughly before refitting the head.

I haven't heard a lot about M103 cylinder head cracks but I wouldn't leave it to chance with a visual inspection. Have a shop do it while the head is out. Besides, you probably want to have the valve guides checked while the head is out.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

K JUUL, I was wondering if you have any problems with oil consumption with your 300se. I have an 89 and on an 800 mile trip, it will consume about a quart to a quart and a half. I have had a valve job done and it has not been corrected. I know of at least 2-3 others here and in my town with the same car that has the same problem. Just wondering.

Scott

I'm at about 220K miles on my 91. Over the last 3-4 years I estimate my oil usage at about a qt every 1500-2000 miles. I have a visible leak near the front of the engine, either the head gasket or the upper timing chain cover or a combination. Plugs show no sign of burning oil. I would estimate that 85% of my driving would be considered on the road as opposed to in town. I have a very incomplete history, I think I am the 4th owner so not sure if any work was done before me. I'll be interested to see how the oil usage changes after the head gasket is replaced.

Be very careful messing with your heads any. Heads seem to be a very touchy subject as far as oil consumption on the straight 6's. If you are using/consuming a quart every 1500-2000, from what I have been told, this is well within specs. All I can say is be careful. Mine consumes about a quart to a quart and a half every 800 miles. That's not within specs.

I bought one of the $25 special 12mm 12-point sockets, and it worked great, but I did recently see a set at Pep Boys with a 12mm in it. my bolts were so tight we had to pull as hard as we could with an 18 inch breaker bar, and hammer down on the socket to break the bolt loose. When installing, it's the scariest thing I ever did to a car; you torque to 50 lb-ft, then add 90 degrees, then ANOTHER 90 degrees. That last quarter turn will feel like you will certainly break the bolt off.

That being said, maybe the Chinese Pep Boys special will hold up, maybe not. Also, I think I would just replace the head bolts on principle, not too expensive, and when you are cranking that last qtr turn, you will appreciate having them. The thought of breaking a bolt is not a pleasant one.

Mine leaked water at exactly the same place, must be common.
Before, it would use a quart of oil on the the highway in about 3-400 miles. I had the head reworked with valve job, seals and guide bushings while it was off, and the oil consumption dropped to negligible.

Worst part of the whole job was getting the chaine tensioner back in - gotta push hard and turn with something at the same time. I made a tool from a bolt head and a nust that worked okay, just be inventive and patient.

Replaced head gasket/valve stem seals and the infamous U-gasket towards the front at about 90K. I was using about a qt. every 800-1000 miles. Plugs were bone dry; however, a tech who no longer responds here once said that 103 motors mask oil consumption.

I was not experiencing coolant loss @ #5 or anywhere for that matter.

I now add about 1/2 qt. every 2000 miles. It's been said elsewhere(and maybe here) that 103 motors DO use a bit of oil.

A pro who posts here by the name of "joe p" has the expression "If it leaks, it's German" in his avitar.

These cars are definitely not as oil tight as their Asian counterparts.

The Powerbuilt brand of 12 point bits set I got at Pep Boys held quite well through my M103 head R&R. I thought my arms would give through the last quarter turn with a 24" breaker bar.

I think it was in the 4/86 issue of Consumer Reports, of all places, that I read that the M103 (300E) has an appetite for oil at revs. They believed it to be by design.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD