Massive oil leak - Valve cover, doggy performance - PeachParts Mercedes-Benz Forum

alexl · #1 03-08-2024, 05:25 PM

Hi folks,

Saga continues on the 300TD I am waking up from a long hibernation. Went on a test drive yesterday, went well. That is until i got it back in the garage and a quite large puddle quickly formed under the car. puddle is forming under the bellhousing, but tracing it up to the passenger side valve cover gasket (there is a plate that appears to guide all of the oil to the rear of then engine - causing me to immediately panic of large rear main seal leak

)

Last night i removed the valve cover, cleaned up the surfaces and reinstalled, properly torqueing. I idled the car quite a bit today and it appeared to fix the issue, but then i went for another drive and got home to a similar leak (though not as bad this time). Of course i am ordering a new gasket, but also asking around if i should be more concerned or if this is an occurrence that happens from time to time?

Also: performance is quite slow "out of the gate", but only sometimes. Sometimes the car can't get out of its own way until 15-20 mph, sometimes it immediately accelerates (as quickly as expected, i suppose).

so far i have:
1. tested compression (300psi+ all cylinders)
2. Had injectors cleaned and tested (1950-2000 psi all)
3. Adjusted valves
4. Diesel Purge
5. New filters
6. Checked Banjo fitting/bolt (no buildup)

Sugar Bear · #2 03-08-2024, 06:54 PM

Wait to see what the VC gasket does for the leak.

For the varying performance, is it starting off in the same gear each time? There is a 1" long U shaped vacuum hose on top of the injection pump that may be failing.

Is there ever a problem with power on the highway? I'm wondering about a clogged strainer in the fuel tank due to sitting.

dieselbenz1 · #3 03-09-2024, 11:29 PM

Check your air filter

Benzman53 · #4 03-10-2024, 04:08 PM

I had leak issues with Reinz and other aftermarket valve cover gaskets; switched to MB and no problems.
My 1980 300SD was doggy off the line similar to yours. Checked all the same stuff and finally confronted the ALDA unit. Did not want to mess with screw so removed ALDA and installed a transmission drain plug washer to shim it approx. 1/16” higher. No problem off the line anymore.

Diesel911 · #5 03-12-2024, 12:39 AM

So, is the valve cover leak caused by the valve cover gasket or is it being helped along with too much crankcase pressure? Check the crankcase breather system for restrictions.

Increased crankcase pressure pushes the vacuum shut off diaphragm in the shut off direction. That might account for the erratic slowness issue.

Where does the crankcase pressure come from. Hot gasses going past the poisons, valve guides and from a leaking head gasket. Take the cap off of your coolant recovery tank and see if there is oil floating in it or if it smells like combustion gasses.

300 psi is not a great compression. I can't remember the lowest spec on that. You need to lest the compression for each cylinder and compare them for balance. If there is 2 adjacent cylinders lower than the rest that can be the symptom of a head gasket issue.

It could be you are having sticking piston ring issues. There are some threads on soaking the cylinders in something to free up the piston rings. (Compression test before and after helps you determine if the cylinder soak worked.)

Others have said using full synthetic oil and it takes like 300 miles of driving for it to free up the piston rings.

Not oil leak related. When the throttle linkage pivot on the fire wall goes bad throttle control can be erratic.

With the engine cold and off grab a hold of the throttle arm on the fuel injection pump and keep it from moving. Have someone sit in the car and slowly work the gas petal. Watch what happens throttle linkages and observe where there is paly in the linkages. In particular watch what happens to the throttle linkage pivot on the fire wall.

Each of the throttle linkage rods has a specified length it is supposed to be adjusted to.

alexl · #6 03-14-2024, 10:56 AM

Quote:

Originally Posted by Diesel911

So, is the valve cover leak caused by the valve cover gasket or is it being helped along with too much crankcase pressure? Check the crankcase breather system for restrictions.

Increased crankcase pressure pushes the vacuum shut off diaphragm in the shut off direction. That might account for the erratic slowness issue.

Where does the crankcase pressure come from. Hot gasses going past the poisons, valve guides and from a leaking head gasket. Take the cap off of your coolant recovery tank and see if there is oil floating in it or if it smells like combustion gasses.

300 psi is not a great compression. I can't remember the lowest spec on that. You need to lest the compression for each cylinder and compare them for balance. If there is 2 adjacent cylinders lower than the rest that can be the symptom of a head gasket issue.

It could be you are having sticking piston ring issues. There are some threads on soaking the cylinders in something to free up the piston rings. (Compression test before and after helps you determine if the cylinder soak worked.)

Others have said using full synthetic oil and it takes like 300 miles of driving for it to free up the piston rings.

Not oil leak related. When the throttle linkage pivot on the fire wall goes bad throttle control can be erratic.

With the engine cold and off grab a hold of the throttle arm on the fuel injection pump and keep it from moving. Have someone sit in the car and slowly work the gas petal. Watch what happens throttle linkages and observe where there is paly in the linkages. In particular watch what happens to the throttle linkage pivot on the fire wall.

Each of the throttle linkage rods has a specified length it is supposed to be adjusted to.

Thanks!
The engine does have a fair amount of blow-by, but not egregious. I am hoping some of it clears up with time and use. I installed a new valve cover gasket and noticed a previous owner had filed down the valve cover bosses to allow for more pressure on the gasket. The gasket itself is no longer leaking, but i am now getting minor leaks from the studs on the intake side of the valve cover - likely a result of the combination of the filed down bosses and the -not great- blow-by. I think i will try a copper washer on these studs in hopes it seals up a bit better.

My compression tests were done cold, and the compression tester was a hunk of junk that immediately leaked down the pressure (returned), but i do not have any trouble with cold starts.

someone in the past had also messed with the ALDA. I removed it as an experiment to see if they had damaged the unit, which woke up the car nicely - now to search for a good ALDA unit.

whunter · #7 03-20-2024, 09:55 PM

Quote:

Originally Posted by alexl

Hi folks,

Saga continues on the 300TD I am waking up from a long hibernation. Went on a test drive yesterday, went well. That is until i got it back in the garage and a quite large puddle quickly formed under the car. puddle is forming under the bell-housing, but tracing it up to the passenger side valve cover gasket (there is a plate that appears to guide all of the oil to the rear of then engine - causing me to immediately panic of large rear main seal leak

)

Last night i removed the valve cover, cleaned up the surfaces and reinstalled, properly torquing. I idled the car quite a bit today and it appeared to fix the issue, but then i went for another drive and got home to a similar leak (though not as bad this time). Of course i am ordering a new gasket, but also asking around if i should be more concerned or if this is an occurrence that happens from time to time?

Also: performance is quite slow "out of the gate", but only sometimes. Sometimes the car can't get out of its own way until 15-20 mph, sometimes it immediately accelerates (as quickly as expected, i suppose).

so far i have:
1. tested compression (300psi+ all cylinders)
2. Had injectors cleaned and tested (1950-2000 psi all)
3. Adjusted valves
4. Diesel Purge
5. New filters
6. Checked Banjo fitting/bolt (no buildup)

1982 300TD wagon?
How many miles?
Any idea what state it was in most of life?

My assumption:
300,000 or more miles.
Valve guides are worn out = compression loss + excess oil loss.
The head gasket is seriously beyond life.
The oil filter housing to engine block gasket is seriously beyond life.
Unless you have documented new chain proof, replace the timing chain now.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

300psi+ all cylinders = 250psi lower than my 1985 300SD.

Roughly 325psi when my friend got it; Replaced, Valve guides, head gasket timing chain + guides.

After all the work, compression was 550psi and still is.
edit:
Oops, sorry, I fat fingered the keyboard.
Cylinder compression is 450psi, and at the high end of spec.

It was gifted to me several years later, just before he died.

.

alexl · #8 03-22-2024, 11:13 AM

Quote:

Originally Posted by whunter

1982 300TD wagon?
How many miles?
Any idea what state it was in most of life?

My assumption:
300,000 or more miles.
Valve guides are worn out = compression loss + excess oil loss.
The head gasket is seriously beyond life.
The oil filter housing to engine block gasket is seriously beyond life.
Unless you have documented new chain proof, replace the timing chain now.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

300psi+ all cylinders = 250psi lower than my 1985 300SD.

Roughly 325psi when my friend got it; Replaced, Valve guides, head gasket timing chain + guides.

After all the work, compression was 550psi and still is.
edit:
Oops, sorry, I fat fingered the keyboard.
Cylinder compression is 450psi, and at the high end of spec.

It was gifted to me several years later, just before he died.

.

I have never heard of a head gasket as "beyond life" these either seal or they don't (in my opinion), no reason to replace unless needed. Also, why replace timing chain if stretch is within spec? Timing chains rarely fail like belts do.

Valve guides - agree, will get to those.

Your compression is very high - wasn't the "factory new" compression something like the low 400s?

whunter · #9 03-22-2024, 02:18 PM

Quote:

Originally Posted by alexl

I have never heard of a head gasket as "beyond life" these either seal or they don't (in my opinion), no reason to replace unless needed. Also, why replace timing chain if stretch is within spec? Timing chains rarely fail like belts do.

Valve guides - agree, will get to those.

Your compression is very high - wasn't the "factory new" compression something like the low 400s?

Please read through the data in this link.

Timing Chains Don't Last Forever
http://www.peachparts.com/shopforum/general-information/163604-timing-chains-dont-last-forever.html

Oops, sorry, I fat fingered the keyboard.
Cylinder compression is 450psi, and at the high end of spec.

.

whunter · #10 03-22-2024, 02:30 PM

Quote:

Originally Posted by alexl

I have never heard of a head gasket as "beyond life" these either seal or they don't (in my opinion), no reason to replace unless needed. Also, why replace timing chain if stretch is within spec? Timing chains rarely fail like belts do.

Valve guides - agree, will get to those.

Your compression is very high - wasn't the "factory new" compression something like the low 400s?

OM617 head gasket failure - pictures
http://www.peachparts.com/shopforum/diesel-discussion/285883-om617-head-gasket-failure-pictures.html