is it time to get a new engine ? - PeachParts Mercedes-Benz Forum

briandownunda · #1 10-12-2008, 06:05 PM

Hi all,

I started a thread on the diesel forum about my 1982 240D (see link below)

82 240D lots of oil at breather tube

& it was recommended that I copy this forum for, perhaps some more expert technical advise.

The bottom line is, I have 3 cylinder with 400+ psi and one with 150psi....the car is using lots of oil and runs very roughly at idle.

Based on what I have included in my thread, is it pretty much 100% certain, that I have lower end problems ?

G-Benz · #2 10-13-2008, 06:29 AM

Even before I read your previous thread, I though worn or broken ring(s) on one of the pistons.

Not being a diesel expert, I can't opine on the economics of a rebuild versus a shortblock replacement...

gmercoleza · #3 10-13-2008, 09:37 AM

Must be a broken or stuck ring on that cylinder with low compression.

briandownunda · #4 10-13-2008, 11:04 AM

Please excuse my ignorance, but why is it that squirting oil in a cylinder with low compression can only bring up the compression level if it is the rings that are bad ?

This may be a very stupid question, but, why couldn't a valve that is almost seating, but not quite, cause the same thing to happen ? e.g. the oil is thicker than air, so, for a while it increases the compression til the oil leaks thru the valve at the seat ?

Thanks !

Pooka · #5 10-13-2008, 01:19 PM

You might try adjusting the valves. There are special tools for this but it can be done without them. It just takes longer.

I say this because it sounds like two problems to me. The low compression cylinder has a burnt valve. Nothing will take care of that but a valve job.

Is there a lot of smoke when you start up that then seems to go away? If so you have worn out valve guides. These are normally replaced during a valve job, so that might cure everything.

If the engine is shot you would probable do best to buy a used one. A rebuild is recommended by Mercedes every 250,000 miles, but a well cared for (and I do mean WELL cared for) engine can do twice that.

Check the valve adjustment. I bet that one cylinder is out of adjustment.

briandownunda · #6 10-13-2008, 02:06 PM

I am going to check the valve adjustment next.....any recommendations on where to get the special tools required for the valve adjustment ?

Yes, it does smoke quite a bit when first started, then the smoke does seem to go away as you mentioned.

Do you believe that an increase in compression with oil added to the cylinder could be due to the valve problems only ? The reason I ask is because I know that this vehicle has been extremely well maintained....I have receipts for all oil changes etc.....it just seems surprising to me that the rings would/could go bad with such low mileage.

Thanks

rs899 · #7 10-13-2008, 02:14 PM

You really don't need any special tools. Just a normal 14mm wrench will do- you may need to grind it thinner so have a cheap one at hand to sacrifice.

The bent ones are probably nice to have ( I don't have them), but you may need your money for something else.