Oil pressure prob— advice needed

[Morris]

I have been having low oil pressure problems lately. If I put "shims" on the return spring, my oil pressure is roughly 60 at cruise and 15 at idle. Without shims it is 45 at cruise and 10 at idle. Today, after a long highway drive, my idle pressure dropped to nothing. I would like to address this problem quickly as I currently rely on my Midget for my daily driver. But also, I don not have an unlimited budget or amount of time to work on the car. What would you do?

A) Install an oil cooler. My oil pressure is always worse after a long (20-30 minute) highway drive. And my oil, though fairly new, is dark for it's age.

B) Replace the oil pump. As my cruise pressure seems to be alright, the pump seems like an unlikely culprit.

C) Replace my cam. The 1500 has no cam bearings. When I rebuilt my engine, the journals where questionable. I wanted to replace my cam with one from an early Spitfire. The early spit cam does use cam bearings and both the bearings and cam fit nicely in the 1500. I have since found a source for an early spit cam. Someone had suggested that the symptoms I am experiencing are due to too much bearing clearance.

D) Replace the crank bearings. When I had the engine rebuilt a year ago, they turned the crank. I checked the clearances before assembly. They were on the high side of spec.

 

[healeyboz]

If money is tight, what type of oil are you using?

 

[Morris]

Castrol 20-50

 

[Dave Russell]

I have been having low oil pressure problems lately. If I put "shims" on the return spring, my oil pressure is roughly 60 at cruise and 15 at idle. Without shims it is 45 at cruise and 10 at idle. Today, after a long highway drive, my idle pressure dropped to nothing.

It would be normal for the cruise pressure to increase with shims installed. Since the relief valve is now set to release at 60. It is unusual for the idle pressure to increase at pressures below 60 due only to the shims. A valve setting of 60 is well above the idle pressures of 10 or 15.
UNLESS ---

The valve, also called plunger, is not fully seating at any pressure below it's release setting & the additional spring pressure is somewhat helping the poor seating at lower pressures. This relief valve leakage would represent a larger total percentage loss at low pump flows such as idle, much less loss at higher pump flows. The valve may be worn and or sticking, or the valve seating may be poor. Also, the valve & the spring can wear on the inside of the valve bore so that valve operation becomes erratic.

I would try replacing the valve & it's spring. In the process, also tap the valve plunger into it's seat with a brass drift to possibly improve the seating. Built up crud on the seat & or valve plunger would be reduced by tapping the valve into it's seat. Sometimes the valve bearing surfaces just get so worn that it hangs up in it's bore & doesn't easily seat as it should.

The following doesn't apply directly to your situation but I'll mention it:
The back side of the plunger/spring must be vented to the crankcase somewhere. if this vent is blocked, the inevitable leakage around the plunger will build up pressure behind it & prevent the valve from regulating the pressure. Very high pressures can result.
D

 

[jlaird]

Hap had me put a ball bearing in there to make the seal. Forget the size though.

 

[tony barnhill]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]What about thickening up the oil a bit and using an additive like slick 50? [/QUOTE]
I wouldn't - that's a bandaid that'll hide the real problem & possibly allow more damage.

There's only a few reasons for low oil pressure, you've identified one of them & found that a new spring assembly will increase it somewhat but not solve the problem...now its time to look inside the engine at where the problem lies & fix it correctly the first time.

 

[aeronca65t]

I think you are already running a low-temp thermostat.

If not, put in a 160F thermostat or make a blanking plate out of your old t-stat. And don't run too much anti-freeze (it makes the engine run hotter). 40% AF is plenty.

Be sure that the oil filter you have has not failed and is clogged. It happens.

The oil cooler is as much a Band-Aid as thicker oil. The 1500 has a good cooling system and if everything is decent, you should be fine without one. I don't run an oil cooler in my race car.....one more thing to break.

If you decide to do cam bearing, you may as well pull it all apart.

Drop the pan and look at the oil pump. Sometimes the pump side-plate gets worn from the gears.You can "re-mill" it by sanding it against some fine emery paper on a piece of glass (if you're patient).

While you have the pan off, you could Plastigage the rod bearings (a weak point in the 1500 anyway). If clearance is on the high side, you could just replace with same-size. It will help at least a bit. Be sure that your oil pump pickup pipe is not screwed into the the pump any more than needed. Some of your problem may still be linked to a problem with the pickup...especially if the car is somewhat low on oil.

 

[Morris]

Great advice! Thanks guys.

I just repaired a very small leak at the oil pressure gauge pick up (Duh). I will report back on whether this improves my symptoms.