Low oil pressure when warm, Crushed. Finally get to drive the car and the idiot light comes on Options

[trojanhorsepower]

A bit of background.
My engine (short block) was assembled wrong by a "professional" about 23 years ago before I got it. When I got it I finished assembling the rest of the motor and found the cam timing was wrong. After several posts and help from Jake Raby we found the cam gear had been installed backwards and a new hole drilled to make it fit. At that point Jake had me split the case, mic the cam and crank and get the numbers off the bearings. All that checked out. I rereassembled the engine and everything went well. Now 23 years later I have the engine in the car and it runs pretty well. (using Brad Penn 30wt break in oil) Except the oil pressure idiot light comes on at idle after the engine warms up. Maybe 10 min of driving. Now based on the threads I have read and the books I have there are no components that affect the oil pressure once the oil is warm? The check valves are for cold oil correct? Hot oil should just bypass the oil pressure bypass valves?
So I will change the oil for 20w50 VR1, but really am I just grasping at straws? What can actually cause this other than bearing wear? An out of spec oil pump? Anything else?

Thanks for the help

Peter

[FlacaProductions]

Are you feeding the idiot light from the stock/oem sender?
Can I assume no other gauges monitoring pressure?

if you're using a two-pole, non-oem sender they can trip at a higher level (8psi) vs. where a normal hot idle is probably anywhere from 1.5-7psi. If you use a VDO 2-Pole Sending Unit, the idiot light is triggered at 8psi, and you will be constantly freaking out at hot idle wondering "what's wrong".

good info here - hoping it's just a case of a sender/gauge issue.

https://vwparts.aircooled.net/VDO-80psi-Oil...m-p/v360006.htm

[trojanhorsepower]

Thanks for the reply. I think it is the stock switch, but I will be trying to asses the actual values. Even 8 psi seems low, what is the acceptable warm idle psi?
the link indicates 1.5 - 7 psi at hot idle, that seems insanely low. IS that really the standard?

[FlacaProductions]

Here's what they say at that link: (but I'm sure the big brains here will weigh in)

We don't feel that the VDO 80psi Oil Pressure, 10 X 1mm, Dual Pole Sending Unit is the "right" sender to use for aircooled VW Engines because the oil light comes on at too high a pressure. Stock is 2psi, this comes on at 7-8psi.
Aircooled VW Engines usually have a hot idle anywhere from 1.5-7psi when properly built (Proper sized pump), and using the correct viscosity oil (10psi/1k RPM hot cruise). More pressure than this at cruise causes the stock oil cooler to be bypassed, and oil temps skyrocket. When you size the pump and oil viscosity properly, you should see hot idle between 1.5-7psi.

If you use a VDO 2-Pole Sending Unit, the idiot light is triggered at 8psi, and you will be constantly freaking out at hot idle wondering "what's wrong".

The solution is to use a VDO 1-Pole Sender with the STOCK Oil Light Switch, to get the use of your Oil Pressure Gauge, with the correct operation of the stock oil pressure switch activating your Warning Light.

Regardless, we are offering this for you enthusiasts that want a high warning light pressure instead of the 2psi stocker.

[trojanhorsepower]

Yeah, I didn't understand that. So basically they are setting this up to come on when the pressure is too high not too low right? At 8psi the light would be on all the time on the low end. And on all the time when the engine is cold on the high end. Clearly I don't understand something.

[emerygt350]

No just when below 8 psi. You should get an oil pressure gauge in there to see what is up. It is still not clear which you have, 2 pole or original?

[FlacaProductions]

Stock comes on lower - two-pole idiot light sender comes on higher. So...if you use a two-pole, you'll see the light more often.

But - since you're using an OEM - AND, IF it IS a sender issue - yours might be bad. I'm just trying to go down this path because it's the easiest/cheapest fix first.

I'd swap that sender.

[BillC]

Perhaps the oil pressure regulator is worn or the spring is tired. You could try installing a Tangerine Racing oil pressure relief valve -- https://tangerineracing.com/shop/ols/produc...re-relief-valve

This can be installed with the engine still in the car.

[porschetub]

Yeah, I didn't understand that. So basically they are setting this up to come on when the pressure is too high not too low right? At 8psi the light would be on all the time on the low end. And on all the time when the engine is cold on the high end. Clearly I don't understand something.

Ditch the running in oil to start with ,your choice of oil is great as long as full zinc which I think it is.
Buy or borrow a mechanical oil pressure gauge and fit that for a proper reading off your oil switch with extension hose , ideally you should achieve 75psi cold and around minimal 10psi hot, I don't remember what I got on my last build when hot but 10psi/1000rpm is good.
If these numbers aren't their time to investigate further ,good luck ,cheers.

[flxzcat]

In my car (new to me) the light would often come on with a quick stop when the engine was hot. When I enquired about this, it was suggested to make sure the oil was filled to the upper mark on the dipstick, not the lower which is where it was. This made the difference and the light no longer comes on when the engine is running.

My car has the idiot light and the Factory console VDO pressure gauge, and it was showing 5-8 PSI when the light was on. The light would stay on for a few seconds only.

[brant]

Since you already know the bearings are good/not worn out

It could be a wrong sensor
But could also be a few other things

If the oil relief piston was sticking open due to scoring and dirty bore that’s possible

The other possibility is too much case sealant not torqued quickly enough
Causing the case to have too wide of a gap at mounting surfaces. Causing the loss of pressure at the bearings from wide tolerances where the case halves come together

[Superhawk996]

Never forget about the POS undersized T1 oil pumps if you’re using one of those (IMG:style_emoticons/default/dry.gif)

[trojanhorsepower]

Thanks all!
I ordered Tangerine Racing oil bypass thing. Will change the oil and check the pressure with a tester. I guess at some point I will change the oil pump as well. What is the current recommended oil pump?

[Superhawk996]

I guess at some point I will change the oil pump as well. What is the current recommended oil pump?

Im not sure there is a “good” T1 pump. The excess clearances of the T1 aftermarket pumps is a well documented, known issue.

Here’s what you can do short of switching to an O-ring T1 pump which would require splitting the case which would not be fun at this point.

1) remove it and measure it. If it is an easy slip fit in & out that’s a very bad sign. Measure the pump OD. It should be 2.757” which is basically a light (0.001”) press fit into the 70mm (2.756”) case bore that requires some light hammer tapping. This is the way the OEM T4 pump was set up with respect to clearances. If your pump is loose, shop around, measure pumps and find one that is a better fit.

2) while you have the pump out, make sure you have the gear end clearance set to 0.003”. Excess gear clearance really diminishes idle oil pressure. There are a number of pump cover gaskets out there that are way too thick. Basically the pump should be surfaced so the housing is zero clearance to the gears and then you would be using a 0.003” thick gasket.

If you have both #1 and #2 working against you I wouldn’t be the least bit surprised to have low pressure at idle and a flickering idiot light.

[Jack Standz]

How about option 3?

If the type 1 oil pump has excessive clearance, maybe consider refurbishing a type iv pump. Seems much more the way to go compared to splitting the case. Of course if you're building a motor, a Gene Berg o-ring pump has merit (just buy and install versus rebuilding a 50+ year old pump).

There is at least one post here that covers refurbishing a type iv pump.