Re: High oil pressure? What's max?

["Curt Voss" <curtv@eudoramail.com>]

When I first start my 8v during the summer, say around 60 degrees F with 20w50 oil, it starts at about 80 psi and then drops to around 40-60 psi at operating temperature and freeway speeds. So 5 bar (= about 73 psi) sounds maybe a little high to me at operating temp and normal rpm. But - in my experience the oil temp goes quite a bit higher when the engine's working than when it isn't, even though the coolant temp doesn't. Screaming up hills in hot weather will peg my oil temp gauge at 250 F with a corresponding drop in pressure even though the coolant temp shows normal or only slightly elevated. So I'd suggest if you didn't drive the car before checking the pressure (i.e. warmed it up in the driveway), drive it a few miles and recheck it. If it's still high, get a higher-capacity gauge and see just how high it's going.

As far as the pressure relief valve - as I recall from talking to a VW mechanic a few years back, the relief valve kicks in about 125 psi, though you can get a brief surge as high as 250 psi when you first start the motor before the valve reacts. So generally, if the filter is blowing when you first start the car, I'd suspect the relief valve. If it's blowing after the car's been running even a few minutes, especially during the summer, it doesn't seem to me that the pressure should ever get high enough to activate the relief valve so it wouldn't matter even if it were bad.

I dunno about the oil filter bypass valve, but if you're using a decent quality filter I wouldn't think two in a row would be bad. And don't those only kick in when the filter is dirty and clogged anyway?

---
'86 Scirocco 8V, soon to be sold
'82 Scirocco 1.8 8v - the daily driver
'81 Caddy
'78 Rabbit 1.7L rustbucket in semi-retirement
'86 Celica GTS
'02 PT Cruiser - the wife's boat

On Thu, 30 Aug 2001 18:38:37   Cheapass Ron wrote:
>You may recall that my car blew out the filter seal a few weeks ago (I
>thought I have lost a headgasket).  Well, that happened again soon
>after.  So, I finally get around to refilling the crankcase and
>installing another oil filter.  This time though, Ben Harder came over
>with a sender and gauge, and we hooked that up and started it.  
>
>Cold, the pressure pegged the meter at idle (5+ bar) and gradually
>reduced as the oil warmed up.  At full operating temp (100C), idle
>pressure was maybe 1 bar or slightly less.  So far I'm happy.  But
>revving the engine, not even all that hard, maybe 4000 rpm, the gauge
>pagged at 5+ bar.  IIRC there should be an upper limit where the
>pressure relief valve in the pump opens...right?  
>
>So here's what I'm asking...
>
>-Is anything wrong?  
>-Those of you with OP gauges, what are your higher rpm warm oil
>pressures?
>-Have I found my problem with an inoperative pressure relief valve?
>-Would a faulty filter bypass valve (in the filter housing, according
>to Mr. Bentley) give me these symptoms?
>
>TIA again,
>
>=====
>Ron (Cheapass)
>'87 16V, ("Victor"), '93 Cabby ("Teufelhasen")
>ICQ 108845455
>
>Stupid is as stupid does.
>-F. Gump
>
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