I'm the original owner of a 1991 350 SDL with 177K miles on it now. I would like to keep it.

Engine has been relatively trouble free but head gasket now has a small external leak in the rear on the passenger side. No indication of leaking into the motor. Motor runs fine otherwise.

Indie shop I deal with is not thrilled with replacing the gasket and suggested I try K&W Block Sealer to fix it.

I have a good relationship with the MB dealer where I originally bought the car and they will replace the head gasket for $1,800-$2,200 including a new timing chain (my idea). I have confidence in them and their senior diesel mechanic and I have gotten along great over the years. This mechanic said we could be opening up a can of worms but is happy to do the head gasket job. He wil also do a compression test.

I'm wondering if we should do a valve job while we have the head off and neglected to ask what that might cost? Would appreciate opinions on whether or not to do the valve job? The engine uses about a quart of oil every 1200 miles, mechanic says this is typical.

This car is in otherwise excellent condition, looks great and everything still works.

Am I missing anything else that I should consider here?

Thank you.

Yep, you are opening a can of worms........alright.

But, if you insist on pulling the head, then I'd certainly have the valves done. The guides should also be replaced at the same time.

I wouldn't trust the job to any local machine shop. I've had great success with Metric Motors who knows the engine thoroughly. The cost should be less than $1K........depending on what's required. In the case of the SD, I succumbed to the "while we are in there" syndrome and replaced all the prechambers. All the shafts for the balls were loose and Metric was fairly sure that they would not go more than another 100K or so. The total cost for the 617 was about $1K..........the 603 will be more if you go the whole route.

I'd have the dealer check the height of the pistons against the deck.......just out of curiosity.

I'd not waste a lot of $$ on the head if the rods are the next thing to go?!
Out of curiosity, ask the mechanic if he knows what a set of upgraded rods would run you.

__________________
'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

............you just had to say it........didn't you?

I have no indication of the rod problem so that does not bother me. Mechanic says these are 400K motors if they get past the first 100K and are maintained.

Most if not all of the rod problems I've seen discussed happen before 100K miles and tend to be in cold climates. This car has lived in Florida all it's life.

I'm trying to be optimistic, I am aware of the risks. Trying to figure out if I'm overlooking anything other than the potential rod problem?

Thank you.

if any mechanic told me that 1 gt oil is normal for a 3.5 diesel to use in 1200 miles i would avoid him for sure.
you are at the stage of bent rods and it will get worse pretty fast.
you dont have to believe anything that has been written about these engines here in the forum, but please go read the threads.
its a money pit now, make some wise choices.
larry perkins lou ky
86 old cars(3 are 1991 350 sdl)