MF 135 engine block

[PTOschool]

Engine is AD3 152 Perkins 3 cylinder diesel.

Trying to diagnose very strange air pressure in cooling system. Just replaced head gasket and experienced air pressure in radiator. Performed a cooling system combustion test with leak detector fluid with no indication. Did successful pressure test and vacuum test on the cooling system with no indication of any leaks. Removed fan belt to disable water pump. Plugged overflow tube and attached exam glove to radiator neck and ran cold engine for 15 to 30 seconds. Still have obvious air pressure.

Why no indication of exhaust gas?
Why no leaks on my vacuum or pressure test? Other than combustion, what other source of pressure could I suspect?

Thanks for reading.

 

[Dieseltech]

Did you do the HOT RETORQUE of the head hardware? That's a MUST per the Perkins repair manual.

 

[Jim.ME]

Coolant expands as it gets warm. if the radiator was filled to the top, it would push coolant out the overflow. If the coolant is down in the radiator air will be pushed out as the coolant expands and fills the open space.

Are you certain all the air was out of the block and head before starting? Sometimes air gets trapped inside the engine when the coolant is filled.

What was the coolant level in the radiator when you started it?

 

[PTOschool]

Coolant level is quite low. Water pump is disabled so no action there. I seriously doubt that expansion from heat on a cold engine can be a significant contributor in a 20 second run but maybe I'm wrong.

 

[Ray,IN]

Next step; run a dry and wet compression test. Dry test reveals head gasket problems or ring leakage, wet test confirms ring condition.

 

[Dieseltech]

Still waiting for an answer to my question...

 

[PTOschool]

Interesting point about the hot retorque. I searched extensively for specific instructions on that point before initial startup. I got many conflicting answers, not about retorque but specifically doing it hot or cold. I finally elected to do it hot but realistically it's just warm, because by the time you remove rocker arm assembly and go through the whole procedure, it's not really hot anymore.

This reminds me that I had a very disappointing experience with the head bolts. I searched across the nation for original unused and finally decided to go with the Massey Ferguson, dealer supplied, aftermarket head bolts. Carefully cleaned all bore holes and conditioned with oil. On retorque one of the new nuts completely stripped before we reached final torque. Replaced it but this experience cast a real shadow on the whole job.

My initial questions however, were why didn't my tests indicate any leak of any kind and where could air pressure be generated except in the cylinders? No turbo on this motor...

 

[Dieseltech]

I use a heat gun to check how hot the engine is. Engine should be 190-200 degrees for best results for hot retorque.

 

[used red MN]

My initial questions however, were why didn't my tests indicate any leak of any kind and where could air pressure be generated except in the cylinders? No turbo on this motor...

Hello PTOschool, welcome to YT! Per your username curious if this has anything to do with a student project?
I believe the problem is compression escaping the cylinders past the head gasket and into the cooling system. You can’t get it to show a leak of coolant back into the cylinders because air (compression) under a higher pressure will leak through a minute leak path. However, liquid under a lower pressure will not leak through the same small path in reverse so to speak. The 7 pounds in the radiator may have actually formed a drop or two inside the combustion area but that little bit goes undetected after a couple of compression cycles it’s vaporized. If you are basing part of your test on the fact that the pressure you pumped it to did not drop since there is some amount of air pressureized/compressed in the tank it holds a steady pressure. Say you had the top tank half full and you pump it to 7 pounds. With the upper part of the tank containing that compressed air you could probably leak a half cup of fluid and show no pressure drop.
I have no experience with those combustion gas leak detection kits. By recent discussions on here it seems like they can be hit or miss in terms of accuracy.
I don’t know what to recommend as a fix. I doubt any kind of stop leak would seal against that compression. Curious if you had the head checked or resurfaced? Any type of sealer used and what did the manufacturer recommend? Who manufactured the replacement stud kit? Unfortunately, it looks to me like your only choice is to pull it back off.

 

[Hobo,NC]

Leak detector fluid does not work well with diesel. If you have the tool you can see gas escaping through the fluid as an indicator the head gasket is compromised. Start off cold if its fizzing the fluid in the tool inside of a minute are when you throttle it up a cylinder is leaking somewhere.

Your head gasket may be leaking at peak compression a normal pressure test may not show a leak.

I am not a diesel guy I did check my diesel for leaks. Radiator cap off I remove the valve rocker arms to seal the cylinder then one injector one at a time and induce shop compressed air into each cylinder at the injector port.

 

[Stan Coryell]

How about we start from the beginning.
Why was the Head Gasket replaced?

 

[John Deere D]

Why was the head gasket changed?

Did you follow the Perkins service manual procedures?

I recently completed a HEAD GASKET change out on a 1961 MF 35......3 cylinder Perkins diesel .
And yes....a HOT RETORQUE of the head hardware was completed........

The head gasket was blown ........there had been a previous individual who HAD NOT ran the engine up to190-200..

The PERKINS service manual is a MUST...
The above service manual has both the Perkins Diesel engine used in the MF 135 ....as well as the MF 35.......