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oil pressure woes - help!

PostPosted: Fri Apr 14, 2017 5:31 pm
by jono
I've had an annoying leak from the pump cover of my oil pump for a while now so today I removed the cover and fitted a new O ring.

I restarted the car and raised it back up on the lift so that I could inspect the pump for signs of leaks - I must have had it running on tickover for 2-3 minutes.

When I dropped it back down to turn off the engine I was horrified to note the oil gauge on zero.

I removed the plugs and spun the engine but could still get no pressure. I then removed the pump cover and pressed vaseline into the pump vanes the tried again for a long as I dared - still no pressure.

What has gone wrong? The fact that the car started and did not prime the pump makes me think that the pump is 'bad'. I'm now thinking that perhaps the new o ring is too thick causing a gap between the plate and the vanes in the pump - is this a plausable explanation?

Can anyone make any suggestions?

Is it possible that running the engine on tickover has caused bearing damage?

I now feel inclined to buy a new pump then go from there.


Re: oil pressure woes - help!

PostPosted: Fri Apr 14, 2017 5:40 pm
by promotor
How thick is the replacement o-ring you put in? The rotor needs to sit close the the pump end-plate - increasing that gap can cause you issues as you suspect!

Re: oil pressure woes - help!

PostPosted: Fri Apr 14, 2017 7:15 pm
by mbell
The seal fits need to be thicker that normal 1/16" o ring to seal. I doubt unless it's very over sized it would cause this problem and would compress when tightened. Maybe use a set of feeler gauges between the body and plate to see how much clearance there is.

Is it a elec sender or pipe type?

I'd recommend priming the oil system by putting a pressured oil source (e.g garden spray bottle) on the gauge take off before running a gain. This ensures there us oil on the bearings.

You could also leave the take off slightly open to see if you get oil. Which will tell you if it an oil pressure or sender/gauge issue.

Re: oil pressure woes - help!

PostPosted: Fri Apr 14, 2017 8:42 pm
by jono
Thanks chaps,

it's a capillary gauge with a clear tube so I can see there's no oil going to the gauge nor any movement

I thought the same with the O ring - it's a thick plate and I've tightened it up to the pump body so I'm assuming the O ring will compress into the groove and not resist the clamping pressure applied by the thick plate.

I've had problems priming this pump before so before I do anything else i will fit a new one.

The new O ring is 3.9mm thick. The old compressed one is 3.1mm

Re: oil pressure woes - help!

PostPosted: Sat Apr 15, 2017 8:57 am
by l10tus

Some of the cheap foreign produced oil pumps have a tendency to produce zero pressure at irregular moments, due to the pressure release valve sticking open, inside the pump.

I had this happen recently after successfully gaining good oil pressure whilst running in for 250 miles, then suddenly during a trip out, lost all oil pressure after 1/2 hours constant driving.

It caused major works, in removing the sump to see if the pick-up tube had become loose, (after cutting out the chassis cross member to gain access!), oil gauge rebuild, pre- priming the knackered pump, etc. Let alone the hours of stress thinking about bearings being shot, etc.

Remedy: buy an original Mick Miller sourced pump from Susan - fit and 'job-jobbed'.

No need to prime or anything, just install the proper pump and start the engine - instant standard oil pressure.

About ?60 as I remember, fit and forget oil pump woes!