Thread: 3.9 v8 oil pressure

How many ks has your transplant got on it?

You could need a bottom end rebuild but it sounds like you are losing oil from the pump while stationary, the oil is draining away and it takes a little while to pump oil back into the system. There must be a drain valve somewhere that needs attention.

It's got 250k on it. When I pulled it half apart to do cam, chain, lifters etc I noticed the front cam bearing was scored a bit. I got them all replaced. The old cam and lifters were stuffed. My guess is the cam should have been changed at about 180k. I was told that the serp motor crank driven pump delivers about 10psi more than the distributor driven pump and that the oil galleries are slighlty larger on the later motor.I was thinking maybe this is why it takes a little longer to come up to pressure because I'm using the earlier timing cover with the serp block.

The motor is quiet as a mouse, no knocking noises, no smoke and no leaks .......yet lol.

Originally Posted by milld

I have a slight concern with my recent motor transplant. (serp motor with v belt timing cover etc. I've noticed that on first startup the oil light can take up to 8 seconds to go out.

Service the oil pump

Check and clean the pressure relief valve ....
Buy new pump gears and install
Install new (pump) gaskets
Pack the pump real good with Vasoline

Fire up the motor and see how it goes ....

Then.......


Fleabay >>>> Buy a mechanical oil pressure gauge ($25 Cheapy is OK)
Coventries >>>> Buy an extra brass connection piece with olive, for connecting it to the oil pump (You will have to cut a new thread on the brass fitting, to install to pump housing) .... as the supplied 1 with gauge won't fit.

Remove the oil pressure switch and replace with oil gauge.

Now you will be able to actually read the oil pressure, instead of guessing


Cheers
Mike

on ebay there are gauges sold by a block called "veethree11" i have bought a voltmeter from him, top quality and good service price was around $40-$50 he has a range of different gauges

Suggestions in order of complexity:

1. Replace oil pressure switch
2. Replace oil filter, anti drain-back valve may be faulty.
3. Replace oil with Penrite HPR Gas 20W 60
4. Remove oil pump gears, face cover and replace gasket. Pump can be primed using a power drill, forget the vaseline.
5. Remove sump and check/replace pickup pipe gasket on block lower face. You may be getting drain back due to a small air leak into the suction gallery.
6. Remove timing cover and replace with another, gasket issues here too.

Just as an additional thought, I had an oil pressure switch fail (as in started to spray oil from where the spade terminal) and in the week before it started to leak it took about 5 seconds to go out. As soon as I replaced it the same old half second light duration returned. As others have suggested, there's no substitute for a pressure gauge though.

I had a similar problems on my 1990 3.9 Vogue, took about 8-10 seconds for oil light to go on on a cold start and 3-5 seconds on a warm start.

Problem was poor anti drainback valves on the oil filters. I tried Fram, Britpart & Wix, all had the same problem. Used a slighly more expensive Mahle OC 261 filter and now the light goes out immediatley even when when the Range hasn't been started for a month. I havn't tried a Genuine Parts filter as they are $40+ here in NZ, but I think they are half that in Aus and are probably better again.

I've been using Penrite HPR30 20W-60 oil which has plenty of ZDDP which is essential in Rover V8s to prevent cam wear. But being a serp engine which has a better oil pump you could probably use the Penrite HPR15 15W-60, has more ZDDP too.

Thanks so much all for the suggestions, I will try another filter first, i'm using ryco z89 at the moment but I'll try the brand that was suggested. Then I'll get another pressure switch. I hope it's not the oil pickup, sucks to remove the sump. Just to clarify things, it was an ex serp motor, I put the v belt cover on it. I think I'll get a pressure gauge too. I pulled apart the oil pump and inspected the gears before I Put the motor in- looked perfect.

Thanks so much again