87 300d blue smoke??? - PeachParts Mercedes-Benz Forum

winmutt · #1 12-26-2007, 11:23 AM

This guy is selling a 87 3.0 6cyl W124 for cheap. Claims mechanic diagnosed it as a blown valve stem seal. What do you guys think? Haven't gone to see it yet but he says there is alot of blue smoke. What engine is this? Turbo? I know there is the potential for blown rings or bad valves. Any way to get an idea without a compression check? How hard is a compression check on these? I seem to remember a good deal of work is needed to get to the injectors or GP.

TheDon · #2 12-26-2007, 11:40 AM

om603 probably turbo but they did come without a turbo in some cars

Jeremy5848 · #3 12-26-2007, 12:12 PM

AFAIK, all such cars imported into the USA are turbo. Exception might be a Euro delivery car.

Blue smoke from worn valve stem seals will be worse after the car has been sitting -- oil migrates down the valve stem into the combustion chamber. Deceleration while driving does the same thing.

I have a similar problem with my '87, also thought to be intake valve seals. Not cheap to fix, takes a special tool kit to do on the car or R&R the head to do the seals on the bench.

You should be able to pull the injectors without removing the manifold but even if not, it's not a bad job. I would recommend both compression and leakdown tests once the injectors are out.

If the tests do not show other problems, one option would be to buy the car as cheaply as possible and drive it as-is. Oil consumption from a valve guide seal leak will be worse around town, not so bad on the highway.

To get a rough idea of how bad the compression might be, try to start the engine without allowing any time for the glow plugs to heat up -- just turn the key and let the engine crank. In 60F weather, my 603 will start after 5 seconds of cranking without pre-glow. If you are in a cold climate, that may not work. I think the 603 came with a block heater installed from the factory; you could use that in a cold climate to warm the engine and then try to start it without pre-glow.

Jeremy

winmutt · #4 12-26-2007, 12:23 PM

Good point on the starting the car deal. He said his mechanic diagnosed as a blown valve seal. I will bring some tools and my compression tester and see if he is willing. Stated no oil in the coolant as far as he knew. Cant wait to see it.

the tenor man · #5 12-26-2007, 02:56 PM

I believe that on the 87 300D that the glow plugs glow when the starter is engaged and only shut off when the key is back in position "2".

Therefore, even without waiting for the glow lamp to go out, the plugs are still glowing...I think.

Depending on the mileage, it could be valve guides causing the valve stem seals to wear.

I agree that the compression/leakdown test would tell it all.

The Tenr Man

Bio300TDTdriver · #6 12-26-2007, 03:01 PM

To get a rough idea of how bad the compression might be, try to start the engine without allowing any time for the glow plugs to heat up -- just turn the key and let the engine crank. In 60F weather, my 603 will start after 5 seconds of cranking without pre-glow. If you are in a cold climate, that may not work. I think the 603 came with a block heater installed from the factory; you could use that in a cold climate to warm the engine and then try to start it without pre-glow.

They did come with the block heater from the factory, but the cord was attached by the dealer after delivery. Some have cords attached some do not.