95 Deville Low Oil Pressure at Idle

I have a '95 Deville 4.9L and I recently started to get a low oil pressure warning at idle. It does leak a littlt oil but I try to keep up with it and I change the oil frequently. I replaced the oil pressure switch and the problem persists.

I'm not positive, but I think I may have put 5W30 in last time I changed the oil, could that be too light? Should I try replacing it with 10W30?

I haven't tested the pressure yet but that oil pressure switch was a real pain to get out (and on) is there a trick to it? I've got a pressure gauge, that would be where I'd connect it, right? In hindsight I should have done that while I was replacing it.

It runs great, no engine noise or smoke. Any suggestions would be appreciated.

You can check the op at any port especially the pressure switch port, I would not go further until this is done.

Supposing my oil pressure is actually low, what would be my next step?

Should I suspect the oil pump or should I try to fix the leak? I don't seem to be leaking oil badly, I never see any fresh spots on the driveway but it does seem to build up there over time. I think the leak might be the rear valve cover gasket, there seems to be a lot of grime built up on the top-rear of the engine. I guess I should de-grease it and see where it's coming from.

The oil pump doesn't cost as much as I thought it would and from the manual it looks easy to replace.

I commute 110 miles a day in this car and I hope to keep it going for a while!

Normally if the pressure is low the issue is not just the pump, but internal wear of the bearings causing low oil pressure, start with the test. The leaks are not the issue with low oil pressure.

The pressure was low. I replaced the pump, no improvement. I had a bit of a leak in the oil pan so before reinstalling a gasket I put in a bottle of Gunk Engine flush.

It flushed out a main bearing all twisted into my oil pan.

It seems to be running better now, though. I've driven about 100 miles and no low oil pressure message yet.

Is it possible that a defective bearing could cause less pressure than no bearing?

Does this mean I need a new crankshaft, too? Or can I just replace the bearings?

You need to make clearer what's what here, you found the remains of a bearing in the oil pan, and did nothing about it?! If so, wow, pull down the bearing cap and look at what is going on!

Not the remains, the whole thing, both halves. I can still read the "F-85 GM" stamp on it. The one piece I have with me got curled roughly into a spiral shape. One end (short side) looks ground down, one side (long side) looks like something was biting into it along the edge.

I don't have the knowledge or expertise to change the bearings myself. I read about it in the manual but I don't even know what a plastigage is, sounded kind of scarey to me. If it was a simple matter of switching the part, I might try that. I looked up the part at Rockauto and they have three different sizes, 25, 26 and 50mm, I think. I don't even know which one I need.

I know a guy who offered to do it for about $300 but this is my only transportation right now, I had to get to work today. I have a minivan I'm in the process of fixing, parts came today and I plan to take tomorrow off to put it together. Until then the Deville is it.

Like I said, It seems to make less grinding noise than before, seems to run better too.

I've never worked with main bearings before at all so any advice is appreciated.

Is this going to cost more than it's worth? I don't want to spend too much money on it if it's not going to last. Mom gave me this car when she got a Prius so I've already gotten my money's worth.

If your running this car around town minus a main bearing insert...your gonna be in for a big suprise soon. Best to get that minivan up and running soon IMO.

Those engines from that era were known for lower end noise and premature bearing wear, and if that main brg is gone/missing, the block will most likely be damaged along with the crankshaft as well. The minimum repair will require reboring the main brg journals and installing oversize bearings. U might want to consider installing a used engine before repairing this one.

If your running this car around town minus a main bearing insert...your gonna be in for a big suprise soon. Best to get that minivan up and running soon IMO.

It's close, I've got it stripped down to the rear cylinder block. I need to get a hinged ratchet or breaker bar to get the exhast manifold off. Can't quite reach it. After that I just need to put it all back together... good as new, right?

I've only driven the caddy back and forth to work once. It doesn't make any noise unless it idles in drive for several minutes when hot and I haven't let it do that much at all. This sounds really bad. I don't have the cash for a new engine, i'd rather donate it for a tax credit. Hopefully it will make it the rest of the week, or until I finish the van.

Those engines from that era were known for lower end noise and premature bearing wear, and if that main brg is gone/missing, the block will most likely be damaged along with the crankshaft as well. The minimum repair will require reboring the main brg journals and installing oversize bearings. U might want to consider installing a used engine before repairing this one.

That's what I needed to know. I found the other half of the bearing, it's almost flat. Aren't the main bearings supposed to have a hole in one half? There's no hole in either half of the bearing I found in the oil pan. Could it be a rod bearing? Would that be quite as serious, would I have to get the crankshaft machined still? I really like the car but I don't want to put that much money into it.

Thanks for the advice! :headshake

http://info.rockauto.com/getimage/getimage.php?imagekey=367155&imageurl=http%3A//info.rockauto.com/SealedPower/7256MA_ANG.jpg

If this image from rockauto is what my main bearings are supposed to look like, that's not what it is. There are no holes and no groove. It look smore like:

http://info.rockauto.com/getimage/getimage.php?imagekey=1101900&imageurl=http%3A//www.lightvehicleenginekits.com/images/products_web/CB1351P.jpg

Which is a rod bearing pic from rockauto.

The only difference is there are semicircular tabs and slots at either end.

Is a missing rod bearing as bad?

Worse, I believe that since the oil pressure is good and no knock, this may be old parts from a previous repair.

Worse, I believe that since the oil pressure is good and no knock, this may be old parts from a previous repair.

It's not, the oil pressure still gets low at idle. I think the cold kept the warning from going off the last time I test drove it.

And the bearing wasn't there when I put the new oil pump in a couple weeks ago. I heard it come loose when I started it after putting the enginge flush in it.

But there is no knock, that I don't understand. The rod should be banging back and forth on the crankshaft.

If I can't just replace the bearings myself and be done with it, I think it's going to go to the junk yard or a charity.

Are there any other bearings besides main and rod that could end up in an oil pan?

How much is the next repair going to cost? I don't think this car was meant to live this long.

One other thing I've noticed...

I no longer get the chime with the low oil pressure message and it goes away as soon as I press the gas, before it would keep chiming and display the message several times.

Any bets on how many miles it will go with a missing rod bearing?

It's gone about 250 miles so far...

OK. A bearing is not missing. If a rod bearing were missing it would already have thrown that rod. If it was a main bearing missing there would be no oil pressure at all and you'd have lifter noise like a coffee can full of marbles. Can you post a picture of what you found in the pan?
I believe you have two issues, the first being the notorious 4.9 front main bearing thump. You can check this by relieving the tension on the serpentine belt with the engine running. Does the noise change? If so it is the thump, not serious but annoying. There is a special front main available to cure this.
The second issue is what may be a bogus low oil pressure indication. The 4.9s only seem to do well with AC Delco oil pressure switches. What is in there now? If it is something else you might want to change it out and see where that takes you.
Using 10W30 might be a good idea too. The 5W30 is designed for newer engines with tighter bearing clearances.
FWIW
YMMV

OK. A bearing is not missing. If a rod bearing were missing it would already have thrown that rod. If it was a main bearing missing there would be no oil pressure at all and you'd have lifter noise like a coffee can full of marbles. Can you post a picture of what you found in the pan?
I believe you have two issues, the first being the notorious 4.9 front main bearing thump. You can check this by relieving the tension on the serpentine belt with the engine running. Does the noise change? If so it is the thump, not serious but annoying. There is a special front main available to cure this.
The second issue is what may be a bogus low oil pressure indication. The 4.9s only seem to do well with AC Delco oil pressure switches. What is in there now? If it is something else you might want to change it out and see where that takes you.
Using 10W30 might be a good idea too. The 5W30 is designed for newer engines with tighter bearing clearances.
FWIW
YMMV

The noise it makes at idle, when hot is like a hiss, like metal rubbing on metal that grows louder as it idles. No lifter or valve tapping, no rod knock.

I got the pressure switch from advanced or autozone, I can't remember if it is AC Delco. I beleive it is Duralast and it's new. The warning message only comes on after it's hot and I idle for a few minutes.

I've got a pressure gauge, I'll test it again and post the actual numbers later.

I don't have a picture of the bearing but It looks a lot like the rod bearing picture I posted above. It's thin, maybe a 1/4" and almost featureless except for the little tab and slot and the numbers stamped on it.

I think I've got 20W50 in their now. I have found that the heavier oil I put in the longer it takes to get the warning message. With 5W30 it will go off much more quickly. Before I changed the bad oil pan filter, I was putting straight 40W in as it leaked, that helped a lot too. Might I try overfilling it a little?

I will try relieving the belt tenstion when I get home from work, I guess I can get my wife to hold the break down while I try it.

Thanks for the advice, I hope it isn't as bad as it seems...

Agreed!!

I parked the Caddy and I have since rebuilt the engine in my Ford Windstar (joke if you like) and blown out the transmission seal.

Now I'm back to commuting 110m a day in the Deville. I'm starting to think my money might be better spent on fixing the Caddy. I still never figured out what I found in my oil pan was, still the same low oil pressure at idle. I never actually tested it, I don't think I need to, I can hear the engine rubbing noise increase the longer it idles in drive. I do not doubt the pressure is actually low.

Oil pump and oil pressure sensor are recently installed new.

I just had an idea...

Is there a way to increase my idle speed? It seems like that in combination with heavy weight oil would fix it, until I can get it overhauled.

I can't figure what the rubbing noise is that you are hearing. Can you get someone else who has a bit of engine expertise to listen to it ? Have you replaced that OP switch with an AC Delco? I also wonder if what you found in the pan was actually a bearing, but from a previous attempt to cure the "thump" by changing a rod bearing.

I can't figure what the rubbing noise is that you are hearing. Can you get someone else who has a bit of engine expertise to listen to it ?[quote]

The sound is like a hiss, it seems to get louder the longer I idle but it seems to go away when I start moving again and it definately goes away when I shift into park.

Is this normal and am I worried about a malfunctioning idiot light?

[quote]Have you replaced that OP switch with an AC Delco?

I think I got it at Advance Auto, I will try the AC Delco brand.

I also wonder if what you found in the pan was actually a bearing, but from a previous attempt to cure the "thump" by changing a rod bearing.

I've driven probably a couple thousand miles since finding that, wouldn't a missing rod bearing make a lot of noise?

I have a pressure guage, before installing the AC Delco sensor I'll measure the pressure while idling in the driveway and report back...

The sound is like a hiss, it seems to get louder the longer I idle but it seems to go away when I start moving again and it definately goes away when I shift into park.

Interesting thread.
FWIW I think your 'hissing' noise is coming from your transmission, not your engine, because the noise goes away once the engine is not under load.
It may be a worn transmission oil pump or a worn torque converter.

Occasionally, a transmission can make a bit of a whining sound if the transmission pan filter is clogged. Try dropping the transmission pan, clean it out, replace the filter and gasket and reassemble.
BTW make sure the filter's old O-ring (at the filter neck) comes out)

As for the old item in your pan, I am certain it's a left-over part from an old repair, or possibly from when the engine was made. I have found all kinds of weird stuff left in oil pans, including old gaskets, sockets, nuts and bolts and once, a 1/2 inch combination wrench.

Bearing shells definitely cannot come out of a bearing in one piece unless the cap falls off, which would be an obvious and noisy failure.

As for the low oil pressure, IMO install a mechanical pressure gauge permanently in the car and monitor what the pressure does when warm.

Vintage car enthusiasts generally allow for a minimum of 10psi of pressure per 1000 rpm. Therefore, if you have 8-10 psi at hot idle, 20 psi at 2000 rpm, 30psi at 3000 rpm etc, then you are okay. Just drive the car with the heavier oil and don't worry about it.

A max pressure of 30-35 psi is fine.

Interesting thread.
FWIW I think your 'hissing' noise is coming from your transmission, not your engine, because the noise goes away once the engine is not under load.
It may be a worn transmission oil pump or a worn torque converter
Occasionally, a transmission can make a bit of a whining sound if the transmission pan filter is clogged. Try dropping the transmission pan, clean it out, replace the filter and gasket and reassemble.
BTW make sure the filter's old O-ring (at the filter neck) comes out).

You called it...

My SES light is on now and I checked the codes, the only PCM code is:

P039 Torque Converter Clutch/Viscous Converter Clutch Engagement Problem.

That sounds expensive. :crying:

I'm pretty sure I (partially) chaged the ATF and filter a few months ago, at the same time I replaced the oil pan gasket.

My mom bought this car used when it was a year old and my parents are famous for not keeping up with maintenance. They changed the oil regularly and that's about as far as it goes. When I got it, it was a couple of quarts low on ATF. They say this transmission was rebuilt a few years ago but there's no telling what shape it's in now. I haven't had any problems though, it runs like a bat out of hell.

As for the old item in your pan, I am certain it's a left-over part from an old repair, or possibly from when the engine was made. I have found all kinds of weird stuff left in oil pans, including old gaskets, sockets, nuts and bolts and once, a 1/2 inch combination wrench.

Bearing shells definitely cannot come out of a bearing in one piece unless the cap falls off, which would be an obvious and noisy failure.

As for the low oil pressure, IMO install a mechanical pressure gauge permanently in the car and monitor what the pressure does when warm.

Vintage car enthusiasts generally allow for a minimum of 10psi of pressure per 1000 rpm. Therefore, if you have 8-10 psi at hot idle, 20 psi at 2000 rpm, 30psi at 3000 rpm etc, then you are okay. Just drive the car with the heavier oil and don't worry about it.

A max pressure of 30-35 psi is fine.

I haven't gotten around to testing the oil pressure or replacing the pressure sensor with a Napa part, I'll do that this weekend when I change the oil for something heavier. I'll look into getting a permanent pressure gauge installed too.

:runaround:

You called it...

My SES light is on now and I checked the codes, the only PCM code is:

P039 Torque Converter Clutch/Viscous Converter Clutch Engagement Problem.

I am not sure, but this diagnosis may be related to the electronic parts of the lock-up mechanism, such as the lock-up solenoid or wiring; and not to the converter itself.

I am not sure, but this diagnosis may be related to the electronic parts of the lock-up mechanism, such as the lock-up solenoid or wiring; and not to the converter itself.

Please forgive my ignorance, but I know nothing about transmissions.

Is that something that doesn't require removing the transmission?

If I can get to it with my ratchet, I'm not afraid.

After a quick search...

Autozone has a "Torque converter clutch lock-up and shift solenoid 1st-2nd and 3rd-4th" for $26.99. (OEM is $28.99).

There's also a "Transmission Control Solenoid" for $102.99, looks like it's internal to the transmission.

Any idea where it is located?

Follow up:

I changed the oil and filter with 20W50 a few weeks ago.

I bought a Napa Oil Pressure Sensor but it was the wrong size, I also bought a mechanical pressure gauge. I put the oil pressure sensor that was on there and relatively new back on and bought a brass T fitting and an adapter for the guage and oversided Oil Pressure Sensor but have not put them on. I haven't been getting the low oil pressure warning message.

So, either the heavy weight oil compensated for the problem or re-installing the pressure sensor stopped a false signal.

I changed the ATF and filter while I was at it and looked inside for the TCC solenoid but could not find it. I haven't been able to locate it on the outside either.

The tcc solenoid is under the side cover not in the trans pan.

The tcc solenoid is under the side cover not in the trans pan.

Again, forgive my total transmission ignorance. I don't know where the side cover is. The side of the transmission facing the firewall? Is that something I can get to without dropping it?

If I had it diagnosed at someplace like AAMCO, could they tell me if the problem is in the solenoid or the with the TC itself? I believe I saw AAMCO advertising free diagnosis.

The side cover is just what it says, drivers side where the axle enters the trans, not an easy job, not sure whether you are up to this.

The side cover is just what it says, drivers side where the axle enters the trans, not an easy job, not sure whether you are up to this.

*sigh* probably not. Thanks for the info though.

Update: Got the transmission rebuilt.

I've plumbed in a mechanical pressure gauge and there is no pressure at idle. Pressure does build up when I rev the engine up, so the oil pump is working.

This weekend I plan to take the oil pan off and inspect all the main and rod bearings.

I'll also chech the pick-up tube and screen.

:runaround:

Not sure if this was mentioned earlier in the thread, but these engines (pushrod V8 4.1, 4.5 and 4.9) were fairly well-known for having oil pumps that would wear out pretty quickly.
You can remove the pump and measure the side clearance on the pump gears with a feeler gauge and straight edge. But IMO oil pumps are pretty cheap so just replace it, imo.

I replaced the pump last year when I started having the low pressure warning. I think I re-used the pick-up tube and screen, though. I will double check those. I wonder if I can get a stronger pump?

I know it has SOME pressure because even at idle it pushes the oil through the clear tube on the mechanical gauge.

What's weird is when I first started the car cold after putting the mechanical gauge in, the pressure was great! It was 15 at idle and 32 at 2000 rpm. Then as it warmed up it dropped to almost nothing at idle and, if I remember correctly, about 20 psi at 2000 rpm.

I believe that is one symptom of excessive bearing clearance. If the bearings look good, try using plastic-guage to measure the clearance.

What weight of oil are you using?

You could try something with a wider viscosity range like 10W 40 or 10W 50

I'm using 15W40 now, but it's badly in need of a change.

I think I'm also going to replace the bypas valve in the oil filter adapter. It's suppose to kick in in low pressure situations according to the manual.

The oil cooler hoses are leaky also, I may replace them.

The oil filter adapter cracked open when reconnecting my repaired oil cooler lines and had to be replaced.

Oil Pressure warning is gone!

I ran 10W30 through the Winter with no warnings. Now that it's started getting warmer the warnings came back so I switched back to the heavy stuff.

I am also having that annoying chime for low oil pressure. What do you think you changed that made this stop? I'm running 10W30. I've checked the oil pump and it's clear. thought it may have been something in the engine so I ran an engine cleaner in it and flushed the engine. Still coming on when idling. Can anyone help tell me what needs to be changed?

You should have a true oil pressure test done using a mechanical gage to see what the real issue is.