1976 240d w115 has been sitting and is locked. - PeachParts Mercedes-Benz Forum

C4rest · #1 03-09-2023, 10:05 AM

Hello,

I recently was gifted a 1976 240d which is locked up. (It is a manual 4 speed)
Upon further inspection I have found it is locked up. I have since, tried to bump it over to no avail. I have pulled the injectors and glow plugs and let them sit with Pb blaster. Still nothing. I pulled off all of the belts. Last night I pulled off the oil pan. There is not a spot of rust in the engine. Cam looks good and so do valves. I am wondering if anyone could give me any ideas, before I pull the head.

Thank you for your time!

Todd Miller · #2 03-09-2023, 10:32 AM

The pistons have rusted in the cylinders. Not uncommon in an engine that's been left sitting for years, especially if the reason why it was parked was because it had a blown head gasket.

Sugar Bear · #3 03-09-2023, 11:17 AM

Pull the valve cover and gently move (slight rocking) the camshaft only enough to know that it or a valve isn't stuck.
Does the car roll in neutral?
Does it stop rolling in gear?
Can you feel ANY movement in the crank?
Does each rod wiggle on the crank journal?
Try putting it in neutral and check for crankshaft end play .005-.010" or so.
Good luck!!!

C4rest · #4 03-09-2023, 11:17 AM

Thank you for your reply!

So even if I see no rust in the engine it is probably rusted to the cylinder?

C4rest · #5 03-09-2023, 11:21 AM

Ok so it appears the cam tensioner is shot so the chain is a little loose. I can move the cam a little, and the valves move freely. The car rolls great when in neutral. In first it won’t roll and in fourth the wheels spin a little when rolled down a hill (I assume clutch slipping)
I do not see any movement in the crank. I could only access two connecting rods and they slide side too side freely.

C4rest · #6 03-09-2023, 11:22 AM

There was no coolant in the oil and the coolant was clear and green. It has been sitting 10 years. Oh I also pulled the starter and it was not stuck engaged.

Sugar Bear · #7 03-09-2023, 12:01 PM

How long has it been soaking? I'd try some Marvel Mystery Oil in the cylinders. Let it sit for at least a few days and then put a breaker bar on the crank bolt. Strike the bar in both directions every day. Use less striking force in the CCW loosening direction.

Good luck!!!

C4rest · #8 03-09-2023, 12:23 PM

It’s been soaking for a week or so. I keep it filled up as it is going by the rings over time. I will try that Thanks.

C4rest · #9 03-09-2023, 12:31 PM

It’s been soaking for a week or so. I keep it filled up as it is going by the rings over time. I will try that Thanks.

Sugar Bear · #10 03-09-2023, 12:55 PM

Going by the rings is a good sign. Patience is key on this exercise IF it will work, without patience it is guaranteed not to work.

Good luck!!!

Todd Miller · #11 03-09-2023, 01:15 PM

Condition of oil and coolant is not a definitive sign of a failed head gasket. Head gaskets can fail in a few different ways, including a failure where coolant simply seeps into the cylinder (and when the engine is running, can be drawn into the cylinder). I'm not saying that's what's going on with your engine, HOWEVER, you do have an engine that visually looks perfect where you've inspected, but is still locked up (where you can't see).

If you had a bore scope, you could probably peek into the cylinders, although maybe not on a diesel MBZ head.

Regardless, you have 1 or more cylinders that have rusted solid. The best penetrant is a 50/50 mix of Acetone and ATF (automatic transmission fluid). The acetone causes the ATF to be extremely thin and creep well, and the ATF is extremely high detergent, so it performs a nice cleaning action. That is the preferred "break free" solution.

The fact that when in gear it will slip the clutch is a very bad sign. Normally on a "stuck-from-sitting" engine, you can use penetrant for a few days, and then put the car in 2nd gear, grab the body crossmember at the radiator, and start pushing the car forward and backward, in sort of a bumping motion. Even shoving on the corners of the car, at the fenders (by hand, of course). Using the weight of the car and the mechanical leverage of the transmission, will break the engine loose, and before long, you can rotate the engine a full revolution this way.

I'll go out on a limb and say that this engine needs to be removed, the head and crank pulled, and the pistons hammered out of it from the back side, using a hard wood block as a drift, and a fairly large ball peen hammer, or small sledge hammer. There's no way this will ever be a running engine, as-is.

C4rest · #12 03-09-2023, 01:56 PM

I will try that solution. Thank you for your advice. I imagine you are probably right about it being done for, but I will still try haha. I’ll get some ATF today.

Idle · #13 03-09-2023, 04:12 PM

If you have to give up and need to get another engine then check to see if the auto and the stick flywheels are the same. I know Volvos used different flywheels for the different styles of transmissions so maybe Mercedes did, too?

The killer is many Mercedes engines flywheels and cranks were balanced as a unit. I am sure there are shops that can do this but it would take a removal of the crank to do so.

Todd Miller · #14 03-09-2023, 05:49 PM

Hopefully he discovers that all but 1 of the pistons is ok, and if he can finesse the stuck piston out without breaking it, or damaging the connecting rod, he can soda blast it, free up and save the rings, give the cylinder a hone, and put 'er back together. Or purchase new rings, hone all 4 cylinders (if they aren't tapered, pitted to bad, and have a ridge at the top), and put it back together. It's 17:1 compression, so there's a bit of forgiveness in that if 3 cylinders are tight and firing nicely, it'll start and run and the 4th will start making good compression at running speed, and might in a few hundred miles, seat the rings, and go back to being happy again.

C4rest · #15 03-09-2023, 08:26 PM

So I just pulled the head, and sure enough the two middle cylinders have rust in them. The two outer ones look great. It appears that an animal crawled up the exhaust and made a nest right in the valves. It’s such a shame because the two others still have crosshatching. What are my options now? Could I get new pistons, rings, and cylinder sleeves? Or should I try to find another engine? If it’s not outrageously expensive, I would love to rebuild it. Im still in high school and have some free time. Thanks again everyone for your replies!