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Oil pump leaks
Posted: Sat Mar 18, 2023 11:27 pm
by JerryTR5
So what's the secret of keeping the oil inside the oil pump of a Sprint?
New pump, new O rings, correct pressure relief valve spring. It leaks.
Replace O rings, fit copper washers to mounting bolts (just in case). Still leaks.
No obviouis sign of where it's coming from, it just seems to ooze oil.
Very frustrating.
Jerry
Re: Oil pump leaks
Posted: Sun Mar 19, 2023 6:45 am
by xvivalve
Is it a reproduction County branded pump by any chance?
Re: Oil pump leaks
Posted: Sun Mar 19, 2023 6:29 pm
by JerryTR5
Of course, are there any other?
Re: Oil pump leaks
Posted: Sun Mar 19, 2023 10:20 pm
by cleverusername
Assuming that there aren't any mistakes, like leaving an old O ring in when you replaced it (yep i have done that) and both mating surfaces were clean when it was mounted. The only conclusion left is the pump is faulty.
My advice is send it back to whoever you bought it from and get a replacement.
Re: Oil pump leaks
Posted: Sun Mar 19, 2023 11:06 pm
by xvivalve
JerryTR5 wrote: ↑Sun Mar 19, 2023 6:29 pm
Of course, are there any other?
Unless you are lucky enough to find new old stock, then to buy new today the answer is no. I'd generally fit a tested used item than a County one, but I'm lucky to have a small collection of them. The manuals show how to measure for wear...
The supplier will most likely tell you they've never had a problem previously, but unfortunately both the castings and subsequent machining thereof are poor quality.
Re: Oil pump leaks
Posted: Mon Mar 20, 2023 3:21 am
by Carledo
Everything said above is true, modern replacement pumps are poor quality from the factory. County pumps are notorious for being out of tolerance straight from the box more often than not.
It is sometimes possible however, to "blueprint" the pump yourself. taking a sheet of glass, some fine emery and a suitable lubricant and rubbing down your mating surfaces a tad is hard work but can yield good results.
I'd also like to point out one other possibility, I had a Sprint engine in a customer car that displayed similar symptoms but the pump was an OE one and I couldn't see any leaks around it, just a slowly growing film with no definite source. Since the engine and oil were new, it was harder than usual to see too. It turned out to be a tiny crack at the point where the oil pressure switch screwed into the transfer housing on the side of the block right above the pump, not the pump itself!
One last thing to check, do you have an oil pressure guage? many of these pumps come with an oil pressure relief valve spring that is far too powerful and lets the motor run at 70-90 psi instead of the factory spec 60 max, this is enough to make any standard seal leak a bit! I even had one newly rebuilt engine that had been fitted with a "spin on" filter, that blew it's filter clean off at first start! That made a mess!
Steve
Re: Oil pump leaks
Posted: Mon Mar 20, 2023 10:01 am
by JerryTR5
Thanks for the comments. I've previously considered County products to be at the higher quality end of the market and I didn't think I'd have to blueprint a new pump in order to stop it leaking. Their pistons sem to be OK at least.
However, I'll check (yet again) for weeps elsewhere as Steve suggests.
I have tried the spring that was fitted to the pump and the one recommended by Robsport. That pump's been off more times than a hookers knickers.
I decided that 75 psi at idle was a bit too much so went for the shorter spring.
I do have the original pump which was a bit scored on the end plate. I'll take another look - maybe it is recoverable.
Anyone have sizes and a source for O rings - I need to buy them by the gross at this rate.
Jerry
Re: Oil pump leaks
Posted: Mon Mar 20, 2023 3:40 pm
by dursley92
I just buy the "Oil Leak Kit" from Robsport which has the five "O" rings you need to stop the usual leaks. If that doesn't fix it something weird is going on.
https://www.ebay.co.uk/itm/291842469861
Re: Oil pump leaks
Posted: Wed Mar 29, 2023 8:08 pm
by tony g
Carledo wrote: ↑Mon Mar 20, 2023 3:21 am
Everything said above is true, modern replacement pumps are poor quality from the factory. County pumps are notorious for being out of tolerance straight from the box more often than not.
It is sometimes possible however, to "blueprint" the pump yourself. taking a sheet of glass, some fine emery and a suitable lubricant and rubbing down your mating surfaces a tad is hard work but can yield good results.
I'd also like to point out one other possibility, I had a Sprint engine in a customer car that displayed similar symptoms but the pump was an OE one and I couldn't see any leaks around it, just a slowly growing film with no definite source. Since the engine and oil were new, it was harder than usual to see too. It turned out to be a tiny crack at the point where the oil pressure switch screwed into the transfer housing on the side of the block right above the pump, not the pump itself!
One last thing to check, do you have an oil pressure guage? many of these pumps come with an oil pressure relief valve spring that is far too powerful and lets the motor run at 70-90 psi instead of the factory spec 60 max, this is enough to make any standard seal leak a bit! I even had one newly rebuilt engine that had been fitted with a "spin on" filter, that blew it's filter clean off at first start! That made a mess!
Steve
Me too, even new Jap stuff I strip debur check and rebuild with oil. Sprint wise I'd suspect relief valve piston o ring if not already replaced. Use the Robsport spring- I have checked many springs and some county springs are way too high and some are too low.