Normal Oil Pressure

[JimVillers]

I am still looking for the cause of my low oil pressure.  I pulled the engine; yes there was a gasket under the oil pickup flange.

I checked the bearings and the appear OK; between .002 and 003 inches (I think that that is within spec).   There must be a "smoking gun someplace.   

[JimVillers]

I found a main bearing specification of .001 to .0025.� If that is correct, my bearings are at the outside limit or slightly above.� �If that is the specification I have probably found my problem.� Any thoughts before I get new bearings and have the crank reground?

For background, the block was line bored when all of the other machining was done.  I do not know if that would affect the final bearing clearance.

[JimVillers]

Just to report progress, we pulled the front pulley; first pulling off the sheet metal, then welding a short length of pipe to the remaining pulley hub and welding bolts to the pipe.  See the picture below.  What a B*#. 

Everything looked OK so we pressured the oil system with 20 psi of oil from my pressure beader.  The real oil flow was from the little squirter for the timing gears. 

That leaves the main bearing clearance as the most likely cause of the low oil pressure.      

[1955CJ-5]

If you mentioned the float I missed it...

Is it in good condition? No serious leaks at the joints?

[JimVillers]

I have thought about the float.� It joint seems "loose" since it does not have a seal but I think that joint should be under the level of the oil.� I have another float so I'll clean it up and see how it feels.

Good suggestion.

[1955CJ-5]

I think you are right, the joints are below the oil level....

Just thought I'd mention it...hoping for a simple "fix"....

One other thought...

The relief valve springs and plungers are installed in both oil pumps?

[CJPilot]

I don't think  the bearings being 5 tenths over would lower the oil pressure to 0 at idle.

Have you talked with an engine builder?

Maybe check with them over at the CJ2A page.  Lots of knowledgeable folks over there.

[athawk11]

A cracked upper pick up tube could contribute to low pressure.

Also, check the "note" below...



I have no idea why this is printing so small.

Essentially, the old oil jet was drilled with a .07" aperature.  The newer was changed to a .04" aperature.  It is recommended the smaller jet be used. 

I have heard folks will close this hole off and re-drill it.


Tim

[athawk11]

[Oilleaker1]

How much end float did you have on the crank? .002-.003 bearing clearance should not have caused your problem. You could try blocking off the oil filter feed to see if something is wrong with the canister. Two oil pumps with the same results means the relief valve is working or seated. Very strange you haven't found it. John

[JimVillers]

Hawk .... Good catch, my timing gear oil jet is larger than my largest gauge, 1.5mm (0.06 inches) so I must have a 0.07 jet.� Easy fix.

The end float is an interesting question, I'll measure it tomorrow.� I guess that the idea is that the #1 main lubricates the thrust bearing and if that is too loose, it will loose pressure.�

Oil-Leak .... I blocked off the oil line to the filter and it did not change the oil gauge readings. 

Great thought.� It may not be a single issue but a number of independent items.� I very much appreciate your (plural) comments.

[PeterL]

I rebuilt my engine last year. I am going to yank it as soon as the weather stays above 50 degrees for more than a day.  I suspect the problem lies with the rear cam seat.  Why do I suspect this?
1) tried two different oil pumps - Same result
2) tried two different gauges - Same result
3) I used to work in a machine shop and I am confident it both my initial measurements and my final assembly measurments.
4) End-play was checked and rechecked upon disassembly.
5) I pulled the oil pan last year to check all the galley plugs - all installed
6) removed the front timing cover and inspected the aperture.  I had previously brazed and re-drilled a .040 hole.  I checked with a wire guage all OK.

[PeterL]

Sorry computer glitch- My thoughts continued.

One thing to remember, oil pressure does not equal flow.  I believe I have enough oil flowing.  But somewhere in the system there is a gap that would have gone un-repaired or un-machined during my rebuild.  The only thing that fits this would be the rear Camshaft housing at the rear of the block.  The front housing contains a bearing and is easily repaired by boring and bushing.  However, the rear housing is cast iron and a part of the block.  It is not easily repaired.  This is likely the only thing, due to location and a lack of replacement parts that was left untouched. When did measure it it was .006-.008 out of round.  I did not think this was too awful a the time but I am convinced that at low RPM there is enough bleed by to reduce the oil PSI to near 0.  While at 2k RPM the PSI is 22.  I would bet $100 bucks, that if that was bored and bushed to a 0.001-.002 tolerance my at idle PSI would be 20 ish and at 2k it would be 35-40 ish.

I would bet that you are dealing with the same issue.

Just my thoughts after thinking/checking on mine for the past year. 

[JimVillers]

Peter .... Thanks you; an idea and logic that I had not though about.� I will stop by the machine shop on Monday and look at the rear cam "bearing".� It is one of the few items that we have not measured or investigated.�

Finally someone who has experienced the same problem.  There is nothing new with these old engines, only "old" problems that we have not heard about.  I'll post what I find.

[PeterL]

Another piece to think about.  When you do research you can find references on the web Cj2A website and other places on how to install a bearing into this location.  It is possible but, if you do find you need this repair I recommend a different repair.  Have your machine shop line bore the 2,3rd, and rear bearing housings to accommodate new cast iron bushings.  They are cheep $15 or less each and you can predrill the hole for the oil port.  The labor to perform the task will be less than trying to retrofit a bearing assembly.  If the machine shop does it right and sets the bushing up with a 0.001-0.002" (OD) interference fit and they shrink it with liquid nitrogen, it will slip right in and within seconds it will warm up.  No locktite, no beating with a hammer, and no special pulling tools in awkward positions and it WILL NOT come out.  The fits will be restored to factory, with the same material, fit, and finish.

This is the company I used to use when repairing bearing fits in my old shop.

http://shaverkudell.ca/wp/products/eze-sleeves-list/the-original-cast-iron-series

-Peter