ok, quickly, here's the story... I had an oil leak problem... You could see puddles under it after being parked and when I took it on the highway for a trip or whatever, when I got back My bumper would be "coated" with oil. So, I got the valve-cover gaskets changed, since it was leaking from there a little bit. Oh, also, the whole time this was going on, when it would get good and warmed up, when I'd pull up to a light (in drive) and stop, the oil pressure guage would drop down to almost red and flicker there till I revved up again. So, after I got the valve-cover gaskets changed, it still did all that stuff...lost oil, coated bumper, flickering guage, etc... so, the last time I changed the oil I used a oil treatment that was supposed to be for re-conditioning gaskets and sealing gasket leaks (which I wasn't sure if I believed, but worth a try)and I made sure I put the oil filter on good and tight. So, the current status is this: hasn't lost a drop since the oil change, no oil coating on bumper after highway driving or on the ground under the car. But, when it's warmed up real good the oil pressure still drops down and flickers when stopped (in drive) at stoplights. So, My main question is... (get to it fool!) is the flickering pressure guage normal? is it supposed to do that when stopped in gear? I'm just wondering if I should be worried about it, or not. I thank Ya'll in advance for any info! THANKS! Brant

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Everything I know I learned by messing it up at least once.

 

Oh, I forgot to mention..... it's a 91'RS 305 TBI with headers, no cat, open air K&N...if that helps.... thanks!

 

my car was doing the same thing it turned out to be a bad intake gasket and a bad oil sending unit...

 

Had the same problem a few years ago with my '84 T/A 'coating' the rear bumper with oil. Turned out to be the rear main seal was leaking. Once that was replaced the problem went away.

However I've never had the problem with the pressure- what weight/brand engine oil are you running? And what pressure does the gauge read when it flickers the red light (I assume you have a oil pressure light in with the gauge)?



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Original owner - '84 T/A w/stock 305HO 5-speed

 

I would hook a manual gauge up and see what it reads at idle warmed up.. If the pressure is low, and then you rev it up and the pressure raises up a bit, you most likely need a rebuild.. Your bearings would probally be worn out.

 

No, I don't have (or see) a red light.. I just mean the guage arm goes down almost into the red zone (danger zone I imagine) not in it, yet... just real close. I use 5W-30 because that's what the oil cap says on it... other people have told Me I should use this and that instead. But I don't know the reasons for switching to something else. so, I wouldn't know what to switch to. I use a synth- blend usually. Man I hate hearing the word "rebuild". I've heard the rear main seal is a costly job, too. anyway.. thanks alot! Brant

 

69,

Before you remove the oil pan to replace a rear main seal and oil pump, you might want to consider some options.

First, make sure the oil pressure guage is correct. The instruments in our cars are notoriously innaccurate after aging. Your pressure sensor (near the filter) may be failing. You can verify oil pressure readings with a mechanical guage installed in the oil pressure port at the rear ledge of the block, near the distributor. There is probably a separate oil pressure switch installed there for the fuel pump circuit. Remove the switch and temporarily install a mechanical guage to check the acuracy of the dash instrument. If the dash guage reads low, replace the pressure sensor near the filter (that larger one).

If you determine that the oil pressure is truly low, you might want to consider a switch to 10W30 full synthetic oil. The true synthetic will flow and protect better at cold temperatures than the lighter 5W semi-synthetic, and will provide better lube film strength at higher temperatures. It may be all you need to increase oil pressure to acceptable levels.

Use an AC stock oil filter. Aftermarket filters can cause flow restriction, and this may be enough to drop pressure to dangerous levels if your engine is already a little loose.

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Later,
Vader
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"Make Me Bad"
Adobe Acrobat Reader 4.0

[This message has been edited by Vader (edited September 25, 2000).]

 

My 88 Iroc did the same thing you described, except it knocked at idle. The press. dropped to 0 at idle and was 60 at cold start up. I wanted to repower with a 350 anyways so I pulled the motor. I found NOTHING wrong with my LB9 whatsoever, I was shocked(it has 125K). As Vader says, the gauge can be inaccurate as I have learned the hard way. Needless to say, I am replacing all the senders while I repower...

 

Hey thanks guys...I'll try the oil and filter change first. So,what Ya'll are saying is that the oil guage level should always stay up? Flickering isn't normal? I can't remember this car ever not flickering, so I don't really know... thanks, again!

 

no the flickering guage isnt normal ...it may just be your sending unit is bad or some of the other things above...the first thing i would do is change the oil 5w 30 oil doesnt hold up good under high stress conditions...so go to a higher viscosity oil and see what happens...if that doesnt work try the mechanical guage and see what the pressure reads at normal operating temp...

 

This just brings up a basic 'shadetree mechanic' or in my case 'messy garage/house/yard mechanic' tip... A mechanical oil pressure guage should be laying around your tool bench someplace... doesn't have to be great, just a cheapie from the store with the fittings to hook it up and verify OP.. heck ya can tape it on the windshield and go for a ride even.
Your '91 has 1 sender for both idiot light AND oil pressure guage which makes it a likely suspect. It's by the oil filter. The back of the intake manifold is susceptible to leaks also... that requires intake removal for a good repair. Iroc_z28 nailed that stuff on the head.
Another thing is that excessive blow-by in the engine will force oil out anyway/anywhere it can get out and the rear main is one of those places. If you pull the oil cap off the valve cover while it's running do you get a blast of gases out with some fairly good force or not? If the PCV system is functioning properly then a leak-down test will confirm if the rings are shot. If that's the case it's generally time for a rebuild anyway. A switch to 10w30, 10w40, 15w50 may give you some relief but it won't cure the basic problem. I'm not a big fan of 5w30 and 0w30 seems absolutely ridiculous unless I was living near the arctic circle - and I don't.


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'89 Formula - Thunderchicken - 355 Vette L98/T-5/3.45 9-bolt/black/t-tops - the fun car!
'90 GTA - The GTA - 5.0 LB9/TH700/3.27 9-bolt/black/t-tops/tan leather - the cruiser.