Mep-802A crank no start, high crankcase pressure

[KnuckleDuster]

Well, I just grabbed 2 sets for you and took a peek on line...

ONAN 186-6081 HALF BEARING SLEEVE SET NSFB | eBay

Manufacturer: ONAN. Manufacturer's ID: 186-6081 HALF BEARING SLEEVE SET.

www.ebay.com

I think I paid close to $20 per rod plus shipping.... here's a listing for $3.95
I don't think I can compete with that!

Have you ever dealt with hq motor service on eBay? They have an entire rebuild kit for 299. Pistons and valves included. I also just did some more digging. All 4 pushrods are bent!

 

[Ray70]

I don't think I have ever bought from them, but the price looks good and they have a 100% rating.
For pushrods, I have bought those from Mayi diesel before.
DO not buy the used ones currently listed on ebay, he appears to have bumped his head ( real hard ) just before placing all his lpw4 parts ads!
I will sell you 4 used pushrods way cheaper if you can't find new at a reasonable price.

As a word of caution incase you didn't already know... After you reassembly the motor, do not crank it over for a good 1/2 hour after tightening down the rocker arms or you will re-bend your new pushrods. Personally I let motors sit several hours, then give it 1 rotation and let is sit a another hour or more to ensure the lifters have bled down.

 

[KnuckleDuster]

I contacted HQ on eBay and they list new pushrods for that engine so I ordered them as well as the rebuild kit.
I was not aware of letting the engine sit before cranking, so thankyou for that advice. I wonder if I bent them trying to start it. Is there anything i should be looking at as to why they bent?

 

[Ray70]

I tried looking at your pictures but it's hard to tell, if the valve hits the piston it will hit perfectly flat, but may leave a very faint mark in the top of the piston. I can't see anything in the pictures and the sludge piles on top of the pistons don't show any signs of piston contact that I can see, but it is still a possibility that the sludge buildup caused the bent pushrods. Could also have been caused by stuck valves, or possibly caused by a stuck oil pressure relief valve.
How clean / dirty is in inside of the crankcase and did you pull out the oil pickup tube and the pressure relief tube while you were taking out the rod bolts?
I would definitely make sure the pressure relief valve is spotless and operating correctly while you have the case open. That can cause piston to valve interference if it gets stuck shut.
It could also have been from someone else going in there at some point and loosening the rocker arms ( possibly to perform a leakdown test ) and not waiting long enough after tightening them down before cranking the motor ( possibly also performing a compression test at the same time )

 

[loosegravel]

I contacted HQ on eBay and they list new pushrods for that engine so I ordered them as well as the rebuild kit.
I was not aware of letting the engine sit before cranking, so thankyou for that advice. I wonder if I bent them trying to start it. Is there anything i should be looking at as to why they bent?

I hope everything goes well for you on this!

 

[KnuckleDuster]

I tried looking at your pictures but it's hard to tell, if the valve hits the piston it will hit perfectly flat, but may leave a very faint mark in the top of the piston. I can't see anything in the pictures and the sludge piles on top of the pistons don't show any signs of piston contact that I can see, but it is still a possibility that the sludge buildup caused the bent pushrods. Could also have been caused by stuck valves, or possibly caused by a stuck oil pressure relief valve.
How clean / dirty is in inside of the crankcase and did you pull out the oil pickup tube and the pressure relief tube while you were taking out the rod bolts?
I would definitely make sure the pressure relief valve is spotless and operating correctly while you have the case open. That can cause piston to valve interference if it gets stuck shut.
It could also have been from someone else going in there at some point and loosening the rocker arms ( possibly to perform a leakdown test ) and not waiting long enough after tightening them down before cranking the motor ( possibly also performing a compression test at the same time )

Another little update plus more bad news, got the pickup and relief valve removed. I'm unsure if the relief valve plunger is supposed to move or not but when I went to pull it apart the plunger was completely seized and it was very rusty internally. Heated it up and got the plunger out, it was all galled up and just a mess. So I'll be ordering one of those as well as I think this one is beyond repairing. Ugh!

 

[Ray70]

The check valve definitely need to move. That relief valve could very well be the reason the pushrods got bent. It will also contribute to low/no compression and no-start condition.
Good thing you identified and corrected that issue!

 

[Guyfang]

Another little update plus more bad news, got the pickup and relief valve removed. I'm unsure if the relief valve plunger is supposed to move or not but when I went to pull it apart the plunger was completely seized and it was very rusty internally. Heated it up and got the plunger out, it was all galled up and just a mess. So I'll be ordering one of those as well as I think this one is beyond repairing. Ugh!

Instead or ordering things, post a "Parts Wanted" add in the forum. Three are several people who have parts machines and sell parts.

 

[KnuckleDuster]

Instead or ordering things, post a "Parts Wanted" add in the forum. Three are several people who have parts machines and sell parts.

Thanks for the heads up. Most of the parts I ordered I'd rather not use used parts but if I need anything else I certainly will!

 

[Ray70]

After reading your work done so far again, I would also say that a cylinder bore full of bird seed could have played a role in bending pushrods as well.
To that point, before you throw the head back on, tip it upside down and fill the combustion chambers with diesel, kerosene, carb cleaner etc.
Let it sit and make sure none leaks past the valves into the ports.
These motors tend to bend pushrods WITHOUT bending the valves, but at this point you should be 100% sure before slapping the head back on.
Once you are done with this thing your motor will be pretty much fully rebuilt!

 

[KnuckleDuster]

I've had the head torn down and soaking in my parts washer. My rebuild kit came with new valves, tomorrow I'm going to lap them in and pre-assembled the head. Then I will test for leaks.
Today I got the new pistons and rings installed, new rod bearings, pushrod housings and seals replaced. I'm getting there

 

[loosegravel]

I've had the head torn down and soaking in my parts washer. My rebuild kit came with new valves, tomorrow I'm going to lap them in and pre-assembled the head. Then I will test for leaks.
Today I got the new pistons and rings installed, new rod bearings, pushrod housings and seals replaced. I'm getting there

Did you find out if you had standard or oversized pistons?

 

[KnuckleDuster]

Did you find out if you had standard or oversized pistons?

Everything in the engine is still standard size! I have no reason to believe this engine was ever opened up in the 3400 hrs it's logged so far. Just really hoping after all this it makes power

 

[loosegravel]

Just reading some past forums. How did you do with this DN2M engine rebuild? It sounds like you were just rebuilding the head the last time we heard from you. I hope it runs like a top!

 

[KnuckleDuster]

Just reading some past forums. How did you do with this DN2M engine rebuild? It sounds like you were just rebuilding the head the last time we heard from you. I hope it runs like a top!

Engine runs like a top now! A little smokey but I haven't ran it long enough to seat the rings. My oil pressure gauge is bad so I ordered a new one and don't want to run it long until that's replaced. Other than that it does make power and function how it should!

 

[loosegravel]

Engine runs like a top now! A little smokey but I haven't ran it long enough to seat the rings. My oil pressure gauge is bad so I ordered a new one and don't want to run it long until that's replaced. Other than that it does make power and function how it should!

That's good to hear! I hope you don't mind me asking what the outcome was on this. I absolutely love this forum. But sometimes we don't get to hear the end result of the fixes. I like to log these events into my memory bank (as long as it's working!) and use the information for later. Good job on this unit!