I think I've finally isolated the oil leak on my '91 350SDL. At 75mph or higher, oil spews from the top of the IP around the ALDA or the two other smaller round cylinders at the top of the pump. Is it possible for oil to leak here? Is over pressure causing the leak?

Also, finally found the problem of poor performance; a faulty crossover switch. With the switch unplugged, the car runs 0-60 in about 12sec. FINALLY!

Mav

__________________
'91 350SDL 165K miles
Lovin' her until she blows...
'01 Dodge Ram Cummins 4X4 DWR
Stump pullin' beast...

Sounds like the rubber seal under the vacuum cutoff is leaking -- the ALDA connection is sealed internally.

Not a great big deal to change -- remove the rack position sensor connector, remove the ALDA, take the two screws out, and lift the cuttoff valve off -- it hooks to the mechanism inside with a little projection on the shaft. The seal goes around the bottom part of the cuttoff servo.

Crossover swith or overboost protection switch? There is a low temp control, but that is for the tranny, I think. The one in line with the ALDA is the overboost protetion valve, and if it is on when it shouldn't be, the switch on the manifold is bad. For sure check this out, I'd not run this particular engine overboosted!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Peter,

Thanks for the help! A couple more questions though:

What is the other cylindrical device to the starboard of the vacuum cutoff and forward of the ALDA? It has a wire with a boot attached to its top and seems to have a threaded collar around it. Could this be a source of the leak?

I've gone through about a dozen cans of engine cleaner to find this leak. The problem is that when it starts, oil goes everywhere. The trick tomorrow will be to clean the engine again, and drive it just far and just fast enough to start the leak again without creating a mess.

Mav

__________________
'91 350SDL 165K miles
Lovin' her until she blows...
'01 Dodge Ram Cummins 4X4 DWR
Stump pullin' beast...

Mav:

The IP on my 603 has a three wire connection in front to starboard of the cutoff -- the connection to the rack position sensor -- and a connection, also three wire, to the rear.

Rach position sensor has a locking ring with tab, rotate to the left to unlock, will remove if turned further with the plug off. Very tight.

You may have a variation of this pattern, I've not personally seen the IP on a 350D.

Most likely the seal is leaking or missing on the cutoff, very very likely if it was replaced shortly before you bought the car. I nearly threw mine away with the old cutoff, only looked because there was so much oil in the guts when I went to hook the new one in. A new seal is NOT supplied with the cutoff! If someone wasn't looking carefully, or in a hurry, gues what gets left out!

The IP is pressure lubed, and if you have any blowby at all, oil will be forced out of cutoff hole, making a huge mess.

This isn't a bad repair -- I could do it in about 30 min (after having done it once -- took considerably longer the first time!). If you don't want to bother yourself, have it done soonest. Should cure your oil leak.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Peter,

Thanks for the help on my IP woes.

The good news is that I cured the leak this morning. Apparently the cutoff was the leaker! What I found was there was only one bolt and bracket holding down the cutoff. Of course the missing one was towards the block so off came the intake AGAIN. I had to remove the ALDA to get to the cutoff and also had to fabricate the little bracket to replace the missing one. Hit 100mph in I-75 today and no leak!

The problem I am still having is that with the overboost protection switch 2-wire connector still connected, fuel is cut off at the ALDA. When I pull the plug on the OPS, I have boost. I even replaced the OPS with a new MD part today and still have the same problem. I’m looking for a way to diagnose the problem without replacing any more good parts.

Mav

__________________
'91 350SDL 165K miles
Lovin' her until she blows...
'01 Dodge Ram Cummins 4X4 DWR
Stump pullin' beast...

Mav:

Pull the wire off the pressure switch on the manifold -- it's next to the boost line, small brass screw-in thingy with a wire attached.

If you have boost with the wire off, the switch is bad. If you still don't have boost, the wire is grounded somewhere between the overboost solenoid and the sensor.

Hate to tell you this, but you didn't have to take the manifold off -- the ALDA will unscrew and tip over toward the engine just enough to clear the connector. Much faster than taking the manifold off.

I'd bet someone did a "cheap" fix (on a $68,000 car, no less!) and didn't put the other screw in because it was "too hard" -- then sold the car due to a "major" oil leak. I'm not sure I want to understand this behavior!

Glad you got it fixed, and I think you probably have a bad overboost switch, nothing more!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!