3.8 GT low oil pressure on dash gauge

[Meridivs]

I just noticed the oil pressure gauge on this Pontiac TS GT stays in the red zone at idle and climbs a little out of it at 2000 rpm and higher (never over the first unit).

There's no other warning light or error in the dashboard - just the scary oil pressure gauge.

We brought this car home for repairs after a 600 km trip (370 miles) without any issues in mountain roads or hot weather. Engine temperature was well below the first quarter mark, acceleration was great and there was no strange sounds whatsoever...

When first started cold engine has no lifter or tapping noise.

Do you have an idea what would be the most obvious sign of oil starvation/low pressure on this engine?

Is there any way to confirm it beside the dash gauge?

From your experience with this 3.8 engine what would be the most probable cause for this:
1. defective oil pressure sensor
2. failed oil pump
3. worn crankshaft bearings
4. worn camshaft bearings or other cause

[LMP]

First in line is clogged oil filter..my experience . .specially if you have FRAM installed. This is an unexpensive test. Use anything but FRAM. Going for a more severe cause is an option only after you have checked this out.

[Meridivs]

Oil (10W40) and filter was changed before this 600 km trip - no change in the oil pressure after this operation.

Strange thing is that this engine makes absolutely no funny noises after going for about 600 Km of mountain roads with oil pressure in the red zone?! Is this normal for a 3.8 with no oil pressure - shouldn't there be some lifter noises when cold at least?

Looking forward to your input on what to check next...

[LMP]

OK for this.
I do have funny oil readings that I consider caused by faulty pressure sensor. No technical verifications about it yet but the needle fluctuates randomly up and down, though not in the red zone, but I think the sensor is "scratchy".
Notice the oil pres sender is also a switch to keep the fuel pump working, and it certainly needs some decent pressure to keep the contact....well, maybe decent would be the 5 psi or so that idiot lights are happy with...anyway...
www.avigex.ca/xport/fuelcontrol_iac.jpg
THough the fuel pump is initially triggered ON by the computer through the fuel pump relay, once the engine is running, you should be able to remove the relay and the engine should keep running. I'd test that, not that it would be conclusive, but as "additional info"....
www.avigex.ca/xport/relays.jpg
Of course, with decent access, I'd pull the sensor and install a "real" pressure meter" ........yeah, I have a few waiting for reuse.... for a clear idea before changing the sensor

[Jeffrv]

The oil pumps on these engines use a gerotor ( spelling ?) style pumps, which do wear at a somewhat higher rate that a conventional gear pump, so I think I would e looking at changing that next. This assumes you have put a mechanical test pressure gauge to confirm the dash gauge readings. I understand that there are aftermarket oil pumps that are higher volume, which may help. Not sure where they are available, perhaps Rockauto or Summit racing.
Good luck Jeff

[Meridivs]

Thank you for the real useful info!

Any idea where I could buy a real oil pressure meter compatible with this engine?

I guess it should fit either with the oil filter adapter or oil pressure sender to measure the actual oil pressure on this engine.

I'm from Europe so I can't buy something locally - any online store that carry this type of oil pressure meter would be great.

[Jrs3800]

I am confused as to how these oil pumps wear at a high rate? Generally the Buick V6 gyrator oil pump will last the life of the engine... And if you do have any true oil pressure issues, chances are you have some worn bearings.. I have seen a couple of these oil pumps fail, but that is very few and very far between..

As well there is no high volume that I know of for these engines.. You can get an oil pressure kit that has a higher pressure relief... All 2000+ or so 3800's had this..

For the 92-95 TS the 3800 should have 60 Psi @ 1850 Rpms... 30-40 Psi Hot idle is normal..

As for a gauge, you just need to order a basic oil pressure gauge.. Its also possible that the oil pressure sending unit is failing...

[inafogg]

imo, it sounds like oil pressure switch is your problem.instead of buying a pressure
gauge i'd replace the switch.much cheaper,& if you have no other problems like
valve tap,more than likely its just the switch.

[Meridivs]

I just changed the oil pressure sender this weekend - same reading: idle in the red zone going all the way down to almost nil with a hot engine. The pressure climbs out of the red zone at 2000 rpm or more but barely, still no valve or any other strange noises from this engine so far.

We are looking now for an oil pressure meter to read the actual oil pressure but, as far as things look right now, some serious engine work might be required .

LMP, we have a MANN filter now - the only one that can be found locally for this van in Europe. If ACDelco could change anything for the better I'll order it from the USA (along with a new set of connecting-rod bearings...).

Any idea where we should go from here:
1st engine oil flush to clean the oil pump pickup screen
2nd replace/clean stuck oil pressure valve
3nd oil pump repair kit
3rd replacing the connecting rod bearings
4th other options to consider?

Looking forward to your ideas!

[Jrs3800]

The earlier 3800 TPI had some issues that you should be aware of... Not all of them suffered from this...

In some cases the engine would wear out the #1 Main and #1 cam bearings... They would just be wiped out... From what was understood they had some clearance issues with some of the early Vin L engines, as well some of the little brother 3300 motors suffered the same issues...

So if you yank the motor for bearings this is something you need to look for..

[500hpgtx]

We have a 95TS 3800 with 130K miles. I am running Royal Purple synthetic 10/30w
Oil pressure warm at Idle on dash is maybe 30psi. Max pressure seems to be maybe 40-45 (dash) at 2500rpms........Do not know about the accuracy of dash gauge.
My 2000 L67 3800 is close to 80psi at 3k rpms. Engine has 90K miles. Obviously higher pressure relief in oil pump....cheers KEV

[Jrs3800]

Kev I have had so many senders fail with these 3800's... Its almost annoying...

The van was good till I accidentally broke it... Had to replace it lasted a few months and wigged out... I replaced it again and then it never showed more than 45 Psi.... Replaced it with an AC Delco that told the truth for 4 or 5 months then wigged out...

The exact same goes for my 95 Bonneville...

Funny story... I put a trans in a friends car( 93 LeSabre with the Vin L ) I broke his oil pressure sending unit... I replaced it and its been 100% perfect for 2 years...LOL

30-40 Psi hot idle and 60-65 Psi at 1850Rpms...

The vans series III 3800 is actually doing 65-70 Psi at road speed and 35-40 at idle.. I have only had one sender show me this and that was the AC delco..

For what ever reason I have no luck with the oil pressure senders... The one on the van is fritzing out again... Now and again it will show me 70 Psi... The 95 Bonnie stays between 40 and 100 Psi

Oil pressure gauge on the GM's is funky at best imho...LOL

[Meridivs]

I just ordered a mechanical oil pressure tester before tearing into this engine.

I hope this will be more closer to the truth than the sender.

Keep you posted with the results

[Scrapper]

Originally Posted by Jrs3800

Kev I have had so many senders fail with these 3800's... Its almost annoying...

The van was good till I accidentally broke it... Had to replace it lasted a few months and wigged out... I replaced it again and then it never showed more than 45 Psi.... Replaced it with an AC Delco that told the truth for 4 or 5 months then wigged out...

The exact same goes for my 95 Bonneville...

Funny story... I put a trans in a friends car( 93 LeSabre with the Vin L ) I broke his oil pressure sending unit... I replaced it and its been 100% perfect for 2 years...LOL

30-40 Psi hot idle and 60-65 Psi at 1850Rpms...

The vans series III 3800 is actually doing 65-70 Psi at road speed and 35-40 at idle.. I have only had one sender show me this and that was the AC delco..

For what ever reason I have no luck with the oil pressure senders... The one on the van is fritzing out again... Now and again it will show me 70 Psi... The 95 Bonnie stays between 40 and 100 Psi

Oil pressure gauge on the GM's is funky at best imho...LOL

oil pressure is not that bad even warmed up dropping to 40 to 45psi how many miles on that?

[Jrs3800]

Scrapper...

Hmm lets see... 30 Psi hot idle is normal for all 3800's.. 60 Psi at roughly 1850 Rpms is normal for a 3800 through 1999... Most during or after 2000 have a bit of an oil pressure kit to bump the pressure to roughly 65-70 Psi..

My original engine in my 95 Bonneville was at 161,000 and still 30 Psi hot idle and 60 Psi at 1850 Rpms... Engine in the car now has 85,000 miles on it and has the exact same pressure...

The van with the Vin L engine was 35 Psi hot idle and 60 Psi at 1850 Rpms...
The Vin 2 L26 3800 III in the van is 35 Psi hot and 70 Psi at 1850 Rpms..

My 03 Bonneville 3800 is the same as above, 35 Psi hot and 70 Psi at road speed..


I have had 2 3800 with low oil pressure, one had spun a bearing but still managed 40 Psi at 1850 Rpms... The other was the vans original, had great oil pressure and then started to tank... 10 Psi at idle is not good with an audible knock...lol

For the most part all 3800's should do a minimum of 30 Psi hot idle, and 55-60 Psi @ 1850 Rpms...

The interesting part is that the oil pressure bypass plunger and spring from the newer 3800's can be used in the older 3800's.. so the oil pressure kit for a series II or series 3 can also be used in the Vin L tuned port 3800 as well..