Oil pressure

I didn't find anything when I did the search, but I think that this is a pretty obscure problem. I got an oil change about 3 days ago, which was much needed I was at 6000 miles since the last oil change. So I did it. I have a 91 S-10 Chevy Blazer 4x4 2 door. Close to 200,000 miles. The problem is when i start the truck when it's cold the oil pressure is at about 60, this is going by the gauge. It's always at 50 or 60 when I started it when it's cold. After driving it for awhile and it heats up the pressure will drop to 0. If I accelerate the pressure will go up to 20, but when I stop accelerating it'll drop back down to 0. I looked under the hood and there looks like oil is resting on top of the engine, but when I test the dip stick it shows up fine. I don't understand what it's doing, and I'm worried about the engine seizing. Please help me.

since oil was just changed 3 days ago sounds like your a lucky man... bet there is dirt or some kind of grime in the oil sending unit... replace or try to clean the end of it. :) bet thats your problem

I don't know anything about working on cars. I just know about head gaskets because i blew one out in a jetta and the oil sprayed out all over everything. How much do you think it would cost to have this done?

I don't know anything about working on cars. I just know about head gaskets because i blew one out in a jetta and the oil sprayed out all over everything. How much do you think it would cost to have this done?

Did you change the oil filter?

I got an oil change about 3 days ago... After driving it for awhile and it heats up the pressure will drop to 0. If I accelerate the pressure will go up to 20, but when I stop accelerating it'll drop back down to 0. I looked under the hood and there looks like oil is resting on top of the engine,
Did your gauge drop to zero before the oil change? It's normal for oil pressure to drop at idle in a warm engine, but it shouldn't go to zero. I guess you could try cleaning or changing the sending unit but since it does at times read up to 50-60 psi I doubt that's the problem. When main bearings are worn the psi will drop because of the extra clearance. With 200,000 miles this may be the cause especially if the truck has had long oil change intervals all its life. If this is the case only a engine rebuild will correct the problem but it will probably continue to run fine for quite a while. Just make sure to keep an eye on the oil level.

oil sending unit is simple.. do it yourself.. one wire to the top of it and unscrew it and replace someone here will know the exact location of it. and there cheap. and as blazerlt is gonna say about the oil filter, if you didnt change the filter it could be clogged, but i assumed anyone with any smartz would change the filter with the oil change :)

Did your gauge drop to zero before the oil change? It's normal for oil pressure to drop at idle in a warm engine, but it shouldn't go to zero. I guess you could try cleaning or changing the sending unit but since it does at times read up to 50-60 psi I doubt that's the problem. When main bearings are worn the psi will drop because of the extra clearance. With 200,000 miles this may be the cause especially if the truck has had long oil change intervals all its life. If this is the case only a engine rebuild will correct the problem but it will probably continue to run fine for quite a while. Just make sure to keep an eye on the oil level.

I highly doubt he needs a rebuild or it would have low oil pressure all the time.

I would be looking into installing a new oil sending unit. Probably the cause.

I got the oil change at Jiffy Lube, and I paid for a new oil filter, but I wouldn't know if they changed it or not. But like I said before, when i look under the engine there is what looks to be oil resting on top the block. I know that shouldn't be there, and I forgot to mention that when it drops to 0 pressure it starts to smell like it's burning oil. I guess it could be burning off what is resting there, but it's still scarey, and it still shows as being fine on the dipstick.

Check to see if the oil filter was properly installed and if it is a new one.

with quickie places, make sure you have a new filter and that your plug and oil cap is back on

It looks like a different filter, but my filter is off to the side of the engine compartment. And there isn't any oil over there really. And if the plug wasn't in it wouldn't have any oil in it at all, right?

right if the drain plug was out it would be bone dry, you would have lifter nois.. but if the cap in the engin bay wasnt there, then the pressure woudl be low because of the oil cap being removed

It looks like a different filter, but my filter is off to the side of the engine compartment. And there isn't any oil over there really. And if the plug wasn't in it wouldn't have any oil in it at all, right?

Today go to a mechanic and have them check what filter they installed and if it is right.

I highly doubt he needs a rebuild or it would have low oil pressure all the time.

I would be looking into installing a new oil sending unit. Probably the cause.

If the sending unit can make the gauge show 50-60 psi sometimes how can it be bad? Isn't that about the most for these engines to ever read? Seems to me it would read low or more likely zero all the time if it were bad. I'm not saying for sure he needs a rebuild but...

hmmm after reading this whole thing again i think i read this wrong to begin with. i thought you said it held good oil pressure before the oil change and it just went down after the oil change. after reading again looks like i was mistaken.. sounds like it could be bearings :( once it heats up it creates slop in the bearing thus loosing the oil pressure. the cold oil will fill the slop is why it has good pressure when cold ... but still could be sending unit but doubt it.

^its faulty and giving a bad signal

man thats good news for you!! i am glad for you.. could have been alot worse.

man thats good news for you!! i am glad for you.. could have been alot worse.

dmbrisket51 is not even the guy with the oil pressure problem. It was DataCorrupt.
BTW- the oil on top of the engine and the burning smell (oil on manifolds or exhaust) could just be from the Jiffy boys being too sloppy when refilling and nothing else.

Yeh the burning smell is from oil on the valve covers. My mechanic dumped a quart on mine and it smoked alot till i cleaned it up. In a 91 the OSU is the right of the distributor which is on the drivers side. It will have 2 wires running to it, you need to have the specialty socket to get it out. Head to www.lislecorp.com for the part number then either goto www.drivewerks.com or ebay and put part number in there then just put that on a socket wrench over top of the sending unit and its out. Then to install new one just bend the top a little till the bottom is threaded in the hole, hook up the electrical connector and you are good to go. Mine did that for awhile then i replaced the sender still do not know if it fixed the problem because i changed oil then had it changed 400 miles later when the oil cooler hoses went in.

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Have a 91 blazer 4.3 4x4. Was really good a working on chevys untl all the elec. comp. came out. Have same prob. with the oil press. dropping out to zero. As soon as it warms up the check gauges flutters and the oil press. drops. Didnt have prob. till replacment of the map censsior and oxygen cennsior. Only thing diff. is the oil blows out the oil stick, Since it broke off at the 4th cycle spark plugg head. some times does but not always. No pings or anything, Motor purrs. Do my own matiance dont trust garages. Commplete tune up 2 mon. ago. Oil filter and all.

what if they over filled the engine than the foam would make the senser read funny and a little extra could be going out the filler