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TR2/3/3A Oil pump question

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DavidApp

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On my newly rebuilt engine I am getting about 70 pounds oil pressure at start up and it drops a bit at idle. After the engine warms up to temperature it maintains about 70ish at 2500 RPM and 25ish at idle. After a run of about 25 miles on Saturday the pressure at 2500 was down near 50 pounds and below 20 at idle.

I can not remember what I did to the oil pump during the rebuild. The engine had all new bearings. I thought I had seen some drawings showing the allowed clearances between the pump inner rotor and outer rotor. The spare pump I have has about 0.008" to 0.010" clearance at the closest point that the rotor tips.
The book I have only mentions the clearance between the rotor and cover plate.

As I have an inspection pit removing the oil pump to check it should not be too much of an issue.

David
 
Did you replace the bushing underneath the distributor drive gear? Often overlooked, I think, but it gets full oil pressure from below and any wear in the bore will let oil leak back into the crankcase.

 
Of course the obvious...have you tried the adjuster on the side of the oil filter mount. I would try adjusting the pressure hot at 2000 RPM before worrying about pulling the pump back out. It is highly unlikely the pump is the problem. Most likely it is, first the adjustment, and second an oil gallery problem (missing plug or such).
 
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Hello Randall

Thank you.

Those are the drawings I was looking for. Which book are they in?

I did not replace the bushing under the drive gear. Is it practical to check it from underneath the engine and replace if necessary?

Hello John

Having read back a lot of Oil pump threads on this forum I got the impression the PRV is there to prevent over pressure and getting 70+ on startup I thought would indicate the PRV was holding OK.
Are there some internal Oil gallery plugs that I may have not replaced? It is not leaking externally.

David
 
I would not trust the gauge. I would get a second gauge, a new one to try and then formulate an opinion. I have a few old gauges and on a couple when the engine warms up completely the gauge reads low.
 
The PRV is there to control pressure warm and above 2k RPM. The idle and cold is merely a by product of having the correct running setting. Early in production the pressure was set lower from the factory, and later raised by bulletin:

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There is the front aluminum gallery plug that leaks into the chain cover, several plugs in the crankshaft cross-drillings. Then there is the oil pump drive shaft bushing. All these are possible internal leak areas which can reduce oil pressure. The pump is rarely a cause, unless it has swallowed metal from another failure. If that happens is not only scores the insides, but will crack the drum and impeller. Another, more repro related failure is if the shaft comes loose from the rotor...but that normally gives a pretty drastic pressure reduction.
 
That's a page from the TR4 factory workshop manual
https://drive.google.com/open?id=0B2H2NJt34OffN2FkZjI2NjktNWJiMy00YWExLWIyNjctOTYzNmI3OTg2ODM0

I've not tried it, but I'm pretty sure you have to check the bushing from above, with the distributor and drive gear removed.

I agree, the 70+ psi on cold start probably says the PRV doesn't need to be adjusted. (Unless you are perhaps running very thick oil. I once filled a freshly rebuilt engine with straight 40 weight, and it would peg the gauge after a winter start. Apparently the PRV couldn't flow enough to keep the pressure down. Switching to 15W40 made it act right.)

However, it might be worth removing the valve to check it visually. If it is damaged, or something is blocking it open partially, it could act as a leak when the engine warms up.

PS, I'm gonna ask : When you say "all" bearings, does that include the front cam bearing as well as the inserts in the block?

There are also plugs in the crankshaft throws. Wouldn't hurt to check them while you've got the pan off. If I was frustrated enough, I might even try hanging a source of oil on the oil pump and spinning it with a drill motor with the pan off. You'll see oil dripping from all sorts of places, of course, but any streams might be worth investigating further.

But more likely, I'd shrug off 20 psi at hot idle as being "good enough for now" and just drive it until the weather turns bad again. Maybe go up a grade on oil viscosity. The rule of thumb is 10 psi for every 1000 rpm.

Speaking of which, are you sure you don't have a leak at the fuel pump contaminating the oil?

DavidApp said:
Hello Randall

Thank you.

Those are the drawings I was looking for. Which book are they in?

I did not replace the bushing under the drive gear. Is it practical to check it from underneath the engine and replace if necessary?

Hello John

Having read back a lot of Oil pump threads on this forum I got the impression the PRV is there to prevent over pressure and getting 70+ on startup I thought would indicate the PRV was holding OK.
Are there some internal Oil gallery plugs that I may have not replaced? It is not leaking externally.

David
Click to expand...
 
I think Randall makes a good point about driving the car until you get a feel for it. My experience at least once or twice was the gauge, so the motor was fine. I bought an aftermarket gauge that has the same diameter as the original at the local store and ran that for a while until I got a different gauge.
 
I did crank the PRV down about 1/2 a turn and seem to have a little more pressure now. Will drive in the morning to see how it does when it is up to temperature.

David
 
I recall I had an oil pressure problem when my distributor was not fully seated....

Cheers
Tush
 
Didn’t spot this yet so here goes: are you still running a break in oil? If so I’d wait for a change out to 20W50 then see what you have. The numbers you quote don’t seem too alarming yet to me.
 
Break in oil? Not familiar with special oil for the break in period. I still have the first oil that went into the new engine.

I am running Valvoline VR1 20W-50 and plan to change it at about 1000 miles or sooner.

David
 
Got a chance to put a hundred miles on the tR2 today. Using 10w-30 Mobile One, I get about 70 psi cold at a raised idle. Maybe 75psi cold and revving. Once warm it sits at about 25-30psi at 800rpm, and holds a steady 70psi above about 1500rpm. Hope this gives a reference for a new engine. With 20w-50 I would expect the same as I get, except possibly higher indication when cold.
 
Hello John

When you say warm are you referring to the water temperature reaching 185 or after 20 miles or so of driving? I get similar numbers to you when I hit 185 water temp but lower after a distance that would have got the oil good and hot.

May try another 1/2 turn on the PRV and see if that helps.

David
 
Warm was between 185 and 220 on the gage, with no noticeable difference in that temp range.
 
Hello John

Thank you.

I am presuming that the oil takes a bit longer to reach full operating temperature than the water in the radiator. On a shorter drive I do not see the oil pressure below 60 to 65 but after a longer run it is down near 50.

If the distributer shaft bearing is worn would a new shaft be a wise addition to the order? May just have to pull the pump and check the shaft for play.

David
 
David my money is still on gauge. You can purchase a mechanical oil gauge for the 25 bucks and fish the line up through the **** pit and hillbilly the new gauge in then test drive to check calibration. I would do that before I started through money at aftermarket engine parts. Also I think 50 is fine when you figure in the variables in the older engine and age of the gauge. However, I would say be careful with the new stuff because the lines are usually plastic. I have a metal fitting that fits onto the flex line at the firewall and then to a compression fitting on the new stuff. If you want, I will mail it to you.
steve
 
Hello Steve

Thank you.

I do have an after market gauge with the plastic line that I rwas using before I finished my dash. I could rig that up again and do a run to test that out.

David
 
Fitted the after market gauge this evening but found my spare breaded hose section is leaking. The pressure looked lower during the short run that I did before discovering the leak.

I notice the 2 copper washers at the banjo connection are the same diameter but different thickness. Should the inner one have a larger ID?

How much affect could pickling the engine block have on the distributer drive bearing? I did not change that bearing/bushing after the pickling bath.

David
 
Yes...inner is larger to allow the oil passage to the banjo. The bearing is steel and bronze...I have never had trouble with those in a shop hot bath. If you install the pump drive shaft and wiggle it, you should know immediately if the bearing is loose. It should have enough play to “click”, but not “rattle”.
 
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