cat 426, perkins-4.236 oil-pr/eng-removal

[fitterski]

hi,
my 1st post here

Rebuilt engine just installed by pros, oil pressure is low idle=20-25psi, 2000rpm=30-40psi. I did the build but the pro was supposed to run the engine before the install. There were comm. problems with his employees so it did't get started until after. What's done is done, now i have to manage the issue.

This cat has no oil-pr gauge, only a low-pr horn which remains silent. Is this an urgent issue or can i wait for spring?

The oil pump relief-bypass is accessible with oil pan removal, is it a very likely suspect? Changing the pump requires front cover removal i think. More than that requires engine removal.

I may need guidance material for the engine removal/installation, does anyone know of any. I have the service manual but it's no help for this.

thanks for any words of wisdom

 

[Tinkerer]

No words of wisdom from me . But, a couple of questions if I may. There are too many unknown conditions to recommend a pump or relief spring replacement IMHO.
You are saying you did the rebuild of the motor but you had someone else install it, is that correct ?
Do you have the service manual for it ? If you do what are the specs. for the oil pressure ?
A high of 40 psi seems a little low but not bad.
Were the bearings checked with a plasti-gauge when they were installed ?
What weight oil is in it ?

 

[fitterski]

....a couple of questions....
You are saying you did the rebuild of the motor but you had someone else install it, is that correct ?
Do you have the service manual for it ? If you do what are the specs. for the oil pressure ?
A high of 40 psi seems a little low but not bad.
Were the bearings checked with a plasti-gauge when they were installed ?
What weight oil is in it ?

The pro removed the engine and also reinstalled it as I was not well equipped for that. I built it but didn't have all the accessories with it for a startup. It seemed like a no brainer for him to do the first start. I had packed the new pump with petrol jelly though some crank turning probably got in there before the first start.

There are two manuals involved, the cat-426 and the perkins which is a pretty sad excuse for a manual. The perkins states MINIMUM 30psi *at rated power*, 37psi if a 'turbo' engine. The engine is a "C"4.236 which stands for 'compensated'. It has a turbo but only some of the turbo engine parts, like pistons. I suspect that technically I could be safe but 'minimum' still seems like not that great on a new build. I was hoping to hit on some Perkins gurus who might tell me not to worry because that engine is a notorious low-pressure one.

The oil is 15w40, all the bearings were double plasti guaged using both the red and green side-by-side for a complete picture, all tightly in specs. Crank, cam, all were very close to new specs. The engine could have done without a rebuild actually. I 'should' have checked the bypass valve but didn't as i was not aware of any history.

I had never touched a perkins before but I also built a cummins 5.9 more or less at the same time and it gives 80psi cold 60 psi hot at high idle.

 

[kshansen]

Were all bearings replaced or measured? By all that means camshaft, rocker arms and the rocker shaft(s)? Was the oil pump rebuilt, gear clearances and end clearances checked? New relief valve spring(s)?

 

[joe--h]

What oil pressure did it have pre overhaul?
I have that same 4-236 engine in a MF50. Oil pressure went to zero. Pulled the pan & cleaned the relief valve & shimmed it with a couple (I think) washers.
Now has 70# at idle. Too much shim but not pulling that pan again.
I think you can get the pump off without removing the front cover, just don't mess up the timing on those counter weights.
Clever of them to put the relief valve in the pump instead of somewhere accessible.
And I have the MF factory manual. Sorriest excuse for a manual you can find.
Joe H

 

[fitterski]

Were all bearings replaced or measured? By all that means camshaft, rocker arms and the rocker shaft(s)? Was the oil pump rebuilt, gear clearances and end clearances checked? New relief valve spring(s)?

Except for he cam all new bearings, new piston pin bushings. The head s complete & new just did the lash. The oil pump was complete & new. Didn't touch the relief, should have because at least I would now know that it wasn't IT.

 

[fitterski]

What oil pressure did it have pre overhaul?
I have that same 4-236 engine in a MF50. Oil pressure went to zero. Pulled the pan & cleaned the relief valve & shimmed it with a couple (I think) washers.
Now has 70# at idle. Too much shim but not pulling that pan again.
I think you can get the pump off without removing the front cover, just don't mess up the timing on those counter weights.
Clever of them to put the relief valve in the pump instead of somewhere accessible.
And I have the MF factory manual. Sorriest excuse for a manual you can find.
Joe H

Thanks, now at least I now know that the engine will pump 70psi so there's little doubt left that my 40 psi just isn't good enough. It'll make the winter but it's gotta get fixed in the spring. And yeah, that's a pan and a half ain't it? I've never thought of using jacks just to take a pan off, hehehe!

The Perkins 'manual' you gotta go through the whole thing each time you wanna find something. I didn't check the pressure before the build, the 426 has no gauge only a horn.

 

[Nige]

To get detailed specs needs a Cat Serial Number, but I looked at a 426 at random and found this regarding the lube system relief valve ..........
Pressure setting (when the valve should lift) ... 345 to 415 kPa (50 to 60 psi)

 

[fitterski]

To get detailed specs needs a Cat Serial Number, but I looked at a 426 at random and found this regarding the lube system relief valve ..........
Pressure setting (when the valve should lift) ... 345 to 415 kPa (50 to 60 psi)

thanks, looks like it might have an obstruction stuck in it or, more likely, a weak spring. Is it possible for a spring to weaken THAT much?

 

[Nige]

That info may be incorrect for your machine, I picked it at random. Need a machine Serial Number to get correct info for your particular engine

 

[kshansen]

Yes a S/N sure would help get good answers!

As I'm not real familiar with the engine, is the relief valve part of the pump or a separate component?

If separate very possible it is worn, spring or other parts like the seat or plunger. Should be a standard procedure to inspect seat and test or replace spring when doing a rebuild.

 

[joe--h]

Piece of something stuck in it keeping it open probably.
Joe H

 

[fitterski]

That info may be incorrect for your machine, I picked it at random. Need a machine Serial Number to get correct info for your particular engine

The cat is #7BC01181 the engine is # LH70202U168588P and the latter of the two is a real can of worms; many kit suppliers will give you the WRONG pieces for it as I have found out.

 

[fitterski]

Yes a S/N sure would help get good answers!

As I'm not real familiar with the engine, is the relief valve part of the pump or a separate component?

If separate very possible it is worn, spring or other parts like the seat or plunger. Should be a standard procedure to inspect seat and test or replace spring when doing a rebuild.

From what I see in the glorious Perkins manual the pump output leaves it via a pipe to a delivery/relief block bolted to the bottom edge of the crankcase. The valve is in that block and not in the pump so it's accessible with a pan removal. Relief should trip @ 50-60/70-80 psi for normally-aspirated/turbo engines. Doesn't say boo about compensated engines but i'd be happy with either figure. And yeah, with perfect hindsight I 'should' have checked it.

 

[Nige]

The information I found before is correct for your machine Serial Number 7BC01181 - see below.
Like other posters above I can't believe that tearing down and rebuilding the oil pressure relief valve was not contemplated as part of the engine rebuild.

Regarding your engine number - instead of the Perkins S/N on the plate, try using Cat data as follows. Engine model D4.236, S/N 001-68588. It may limit the number of places that would recognize it but should ease your problems of getting wrong parts.
BTW the S/N of the driveline installed in your particular machine is 00G-71982.

 

[fitterski]

The information I found before is correct for your machine Serial Number 7BC01181 - see below.
Like other posters above I can't believe that tearing down and rebuilding the oil pressure relief valve was not contemplated as part of the engine rebuild.

That was the 8th engine and the third diesel I ever built, that's how. I probably presumed that the valve was integral with the new pump I put in. The entire episode was a nightmare beginning with wrong parts delivered three times and causing a two week delay each time because the source's suppliers would not drop ship, etc. etc. The last beauty was the idiotic angular piston bushing bores that NO machinist who is not an engine specialist is prepared to work with. Getting those bushings in, all by itself, saw me at 4 different shops spending a total of $900 for work alone. I should have bought the complete piston and rod assemblies. I should have, I should have... it never ends. The alternative was a pro build which was quoted at $13,500cdn with a turbo, about 4 times what I spent and I've seen pro builds blowing prestone into the oil too after a few months.

Regarding your engine number - instead of the Perkins S/N on the plate, try using Cat data as follows. Engine model D4.236, S/N 001-68588. It may limit the number of places that would recognize it but should ease your problems of getting wrong parts.
BTW the S/N of the driveline installed in your particular machine is 00G-71982.

Thank you very much! I've put those numbers away. Now that the engine is rebuilt at 7600hrs and seeing that I put 5,500 on it in 15 years, and the fact that I'll be 76 in a few months.... I might not built "it" again Fact is that each time I bought parts through Cat I always got good ones. This time my son gave me a pro rebuilder as a source for MaxiForce kits and that's how it ended up on the non-Cat route. I like the engine, it's a good engine, but the documentation, aaaarrrrrgggghhhh!

From what I've been told, at the time they were experimenting with an upgrade when the prototypes, and more than just one, went into Cats being produced in England at the time instead of bin-13, or at least to a restricted circle of some sort, badly documented, whaaaaaaaatever. And so the resultant #'s mess.

 

[Nige]

Here's the complete "as built" component list for 426 loader S/N 7BC01181.

 

[joe--h]

LH70202U168588P mine is later 31226*U414561U* The first part is the MF serial #, the U is Perkins. Looking at the MaxiForce kit, $400 for the whole thing seems like they must be crap but how was it other than the wrist pin bushings?
Joe H

 

[fitterski]

Here's the complete "as built" component list for 426 loader S/N 7BC01181.

Thanks old timer, I'll save it out for future ref.

 

[fitterski]

LH70202U168588P mine is later 31226*U414561U* The first part is the MF serial #, the U is Perkins. Looking at the MaxiForce kit, $400 for the whole thing seems like they must be crap but how was it other than the wrist pin bushings?
Joe H

I paid like $2300cdn including pistons, rings, all bearings and gaskets., oil pump, complete head and I don't remember what else. I thought it was GREAT kit, especially the way they packed the rings, nice and orderly, makes it a joy to handle them. BTW I was set to spend an evening gapping the rings but I could not find a single one that was out of spec, in fact they were all center-of-spec. Never seen anything like it b4! Definite kudos there EXCEPT for the # fubar AND the kit doesn't have the seal install rings that make life so much easier (my Cummins kit, forget make, had them). I recommend the kit, as a DIY-er mind you, I ain't no pro!