Drewster67

Anyone have a similar experience? I just find it rather soon for an oil pump to go out after only 32k miles.

My oil pressure has dropped to 6 psi at idle - low enough to trigger the low oil pressure warning.

CaseyJones

I would suspect the sending unit before the pump unless you have larger issues going on that have not been discovered.

Drewster67

Thanks Casey - the sending unit was replaced not too long ago. I changed the oil and found no metal in it also -

The car seems fine when running - no noticeable change.

CaseyJones

I'd still check the pressure with an analog gauge tapped into an oil passage somewhere. Other threads on the subject mention locations to use. The sending units for these cars are notoriously unreliable.

tommypenguin

Did you cut the oil filter open to inspect metal shavings? A lot of times just looking at the oil will not expose metal flakes. Whats your total miles on the car?

Drewster67

I did not unfortunately.

32K on the Thompson short block - and refurbished heads -

When I bought the new short block for Thompson - it came with a new oil pump.

The SB was changed out a 85K and now the car has 117K

Mr. Jones

you can install a mech tube and gauge from the front oil passage located under the alternator to verify the pressure.
Usually the factory sending unit fails with high pressure all the time.

Watch oil temps and level if you have a spun main bearing you will see higher oil temps than normal. Does the pressure always show 6psi or does it start say at 40 and drop as it reaches operating temp?

A failed pump is unlikely, a stuck pressure relief valve is more likely if the motor is sound. Pump would still have to be replaced.

Drewster67

Pressure starts out strong then dips low.

I had the oil pressure sending unit replaced this morning but have yet to run the car (Still at work)

Tech said he started car - pressure reached about 30 immediately and rose to 40+ when throttle was tapped to 2500 RPMS. Unfortunately, the tech was mobile today and had another job to do after mine and he wasn't able to let he warm up to temp.

I will definitely keep an eye out on the oil temps - from what I can remember, the oil temp was within range when warm.

I'm hoping its just the sending unit.

My shop of choice is booked solid for at least 2-3 weeks (if not more) - My car picked the wrong time of year to get sick ... lol

Mr. Jones

A symptom of a spun cam bearing is good oil pressure cold and down to 5-10lbs at idle when hot.

scott1974

I thought i might have a spun bearing because of similar oil pressure readings. It turned out to be the sending unit. I took the sending unit out of the block and laid it on the top of the engine and turned the key to the "on" position and the dash showed 8lbs pressure...thats when that sinking feeling left me because then I knew it was the sending unit.

wcsinx

If and when you replace your sending unit, DO NOT cut a hole in your cowl.

Drewster67

Swapped out the sending unit and no change.

So I'm down to either a bad oil pump/relief valve or the main bearings are going after only 32K miles on this new short block. I'm not sure what else it could be and I'm praying its not the main bearing.

I parked the car and bought a truck so I'm not in any rush (not like before) so I'm going to take my time this time around.

Drewster67

Agreed! No way would I ...

ZZ06

My guess would be a stuck relief valve and not a rod bearing. A spun bearing can sometimes knock. It would be something you can hear at idle and definitely under load.

scott1974

Have you tried a mechanical gauge? two bad sensors in a row is not uncommon.

93Polo

As others have posted C5 oil pressure sensor failure is not uncommon. I pieced together the Buick sensor relocation from Summit and NAPA and it works great. The sensor seems to be much more reliable and certainly easier to replace.

https://www.corvetteforum.com/forums...hese-days.html

GCG

Is anybody doing something similar to TPE's relocation kit (2nd version)?

Drewster67

I actually haven't - I decided to just wait until she goes into the shop on the 29th for diagnoses.

I swapped the sensor for a Borg Warner unit from a local parts store (with lifetime warranty) - the pressure does show stronger but still low at idle once warm.

Drewster67

Motor is definitely quiet - nothing out of the ordinary.

CaseyJones

How low is low?