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Old 09-12-2001, 10:54 AM
Snakeyes_Tx Snakeyes_Tx is offline
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Join Date: Apr 09, 2000
Location: Houston, Tx - US
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This can't be right. It's hot outside and the a/c is on full blast. The temperature gauge is 5/8 the way up.

At 700rpm, In drive at a stop, my oil pressure gauge bottoms out below 0.

At 900rpm, either in Drive with my foot on the gas a little, or in Neutral with my foot on the brake, the oil pressure reads 22psi.

Could that 200 rpm make that much of a difference? It still runs at 40ish psi while I'm moving though.
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  #2  
Old 09-12-2001, 12:20 PM
Bob Barry Bob Barry is offline
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Join Date: Apr 09, 2000
Location: Providence, RI
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The very same thing happened to my GW under similar conditions. Turns out I was a quart low; I added the quart, and it hasn't done it since.

My guess is that the hot oil (10W30 Synthetic, btw) thinned out too much, dropping the pressure. The extra quart added 25% greater volume, meaning it could absorb more heat before it thinned out.

On a side but related tangent, back in college I had a hand-me-down Plymouth Horizon with the 1.7L VW motor that used as much oil as gasoline. I could tell when it was down a quart because the oil-pressure would read 5psi lower on the dinky aftermarket gauge I installed.

Pretty tough motor; it was on that motor that I learned that *some* oil pumps need to be primed before they are installed. Running it for a few minutes with no oil-pressure never bothered the motor a bit.

I suspect that oil-level or oil-viscosity may be the culprit in your case.
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Old 09-12-2001, 01:38 PM
Dive 30 Dive 30 is offline
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Join Date: Aug 31, 2001
Location: Grand Junction, CO
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Dude! This very same problem just toasted my motor. When running cold my motor would keep 40psi no problem, once it warms up and I'm moving (Temp moves to just below half) it would drop to 32-35 psi. Drop to idle and the psi goes away. This is not good, you could hear the valves clacking. The tolerances in the oil pumps are very close. Oil pump rebuild kits are cheap!! And shimming the bypass does not work (my dad said it would). Running 15w-50 is a stupid cheap fix. Rebuild kits are $10-$15. Make sure you completely remove the old gasket (no RTV on this one. One guy recommends 600 grit wet sandpaper to smooth the mating surfaces, I used it and it works. And make sure you torque the bolts (seems to have lots of problems with leaks on these rebuilds). The factory TSMs, Hayne's and Chilton's recommend packing these with potroleum jelly for intial start up. Some guys do it, some guys don't. I did, it picked up right away. I like that. My faith in "that's good enough for me, son" just cost me $1049.00 from autozone for a remanufactured motor. (I'm a little worked up about it). Please, if you continue to have this problem, do not let it go.

edit: And yes, as soon as I gave mine a little gas the psi would pick right up. I now have a quart or more (not an exaggeration) of oil sitting in my air cleaner. My number eight cylinder actually smashed a spark plug, there are netal shavings everywhere.

[ September 12, 2001: Message edited by: Dive 30 ]
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Old 09-12-2001, 05:32 PM
Snakeyes_Tx Snakeyes_Tx is offline
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Location: Houston, Tx - US
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I believe I'll have to agree with Dr. Barry here... I am actually a quart low. When the pressure dropped, the motor never made a low oil pressure noise.. like lifter noise, or valve clatter. I'm running 20W50 oil right now, and until I replace the oil filter (last one wouldn't tighten all that well) I have a small leak that lets about a quart out in 3000 miles. It's almost due for an oil change anyway.
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Old 09-13-2001, 12:18 AM
wagdriver wagdriver is offline
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Join Date: Oct 14, 2000
Location: Orlando, FL, USA
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Sounds like the pump is weak could be that the clearances on it have gotten worn so that is not pumping efficiently as it should. You may have to take a look at it. It could also be a partially blocked in put screen. Dr. Bobs answer is also a possiblilty, let is know how it turns out.
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