Oil pressure way too high

Hey guys, as you can see, I am completely new, but I have been reading on and off for a couple weeks here. Definitely seems like a good crowd.
Anyway,
I just recently bought a 1989 Riviera from my neighbour for cheap and its in awesome condition but there are a few odds and ends that need to be fixed. I have already done some upgrading to it (deck and speakers - all alpine type r. subs and amps are next).
So I am a little mechanically inclined, I do know how to do basic stuff that I learned in high school (I'm 21). So, I did an oil change this weekend and I really wasn't sure as to how much oil to put in the car. (I also have a 2006 Pontiac Pursuit 2.2L ecotech) The pursuit takes exactly 4.7 litres of oil, so with that said, I was assuming that with the Riviera being a 3.8L, it would take more than 4.7 litres of oil. Well I was wrong. So I did the oil change, realized I had way to much oil in it, dumped some out, and went by what was on the dip stick. Dumped a little more out, and from what I saw it was at around the 2nd last dot/hole on the dipstick. So, I knew it was still a little high, but figured it was a good level. So I did some driving around and noticed on the oil pressure gauge that it was way to high (two notches above the middle) when it was idling. When I drove, rpms went up, so did the pressure, to the very top on the gauge. I got home and checked on the internet as to how much oil it needed and it said 4 quarts which is 3.78 litres. So I emptied out about a litre and a half, checked the dipstick and it was at the add 1 QT mark. So I added a little more and now it was at a good level on the dipstick. But now the oil pressure is way to high when idling and shifting through gears, especially at anything about 2000 rpm. And especially when the engine is cold, the pressure goes to the top notch at 1200 rpm.

I apologize in advanced for this big looooong speel, But I figured I better explain fully whats been going on.

The car ran just great before my oil change and it still runs fine, but I'm afraid I'm gonna blow seals or do some serious damage. The car is also at 203xxx kms.
I also used 5w30 oil. should I maybe try a different type of oil?
The owners manual doesnt even say how much oil the car takes. but it tells you how the viscosity of the oil and what not.

Anyways,
Thanks!

Jordan.

Hi Jordan. Welcome. To understand what's going on (if anything), we need to establish some facts. First, when you say the oil pressure is "high", what is the meter actually reading? Depending on that value, it may be high, or it may not. Next, we need to know what the meter used to read before you changed the oil. It would also help to know what is a proper value for your engine at idle and at RPM. Someone may chime in with this info.

Based on what you've described, I'm guessing the old oil was near the end of it's useful life, or beyond it. If it was diluted with contaminants, viscosity goes down, and with it pressure. What you're reading now could be the correct pressure for fresh (good) oil. I don't think the pressure jump was a result of the 5w oil, as a low weight should not raise pressure (you should be using 10w in this engine). This causes me to ask again: what pressure are you reading?

Oh, I doubt you did any damage by overfilling the oil. I also don't think it has anything to do with your higher reading. If the level is in the correct range on the dipstick, you're all right.

...consider buying or borrowing an oil pressure tester. If you buy should run $35 - $60 at an auto parts store. ...if you get from Harbor Freight or another discounter may be much less money (but be advised that quality can correspond to price). You also could really use a copy of the factory service manual. Check on eBay they are usually not hard to find... and a Haynes (not as good as the fac but pretty good actually) is less than $20 on rockauto.com. If you don't have one you really should get one.

If it is any consolation to you, "high oil pressure" usually but not always means the sending unit or the wiring to the sending unit has a problem. This is why I wrote all that stuff about using a tester gauge to check it.

as far as the oil goes -- the owners manual should list oil capacity on the tables in the back near the index. You looked there right? The 89 and 93 were similar cars -- in the 1993 manual it's listed in "Crankcase Capacity" on page 268. See:

http://www.extendedgmwarranty.com/owners-manual/buick/1993-Buick-Riviera.pdf

I am not saying it's there in your owner's manual. I am saying that GM had reused that manual, with model year edits, for many years and that is where it is in the '93 edition, so do you think it makes any sense to double check?

That said, the 3800 had a 4-or-so-qt capacity for *years*... if you have a car with the 3800 that will take the long filter (the PF52) capacity bumps up a little, to not quite 4.5 - just start with 4 and go by the dipstick in that case.

Hope this helps and welcome aboard.

Albertj


EDIT: I forgot to mention that if you check the oil pressure and it indeed is high then you need to repair the oil pump - most likely it has something stuck in it. Someone else will chime in as to if this engine's oil pump has a pressure relief valve of some sort.

I am not 100 percent sure what its reading. On my drive home from work in the morning I'll take mental notes. (I work night shift). And I'll get back to ya. But I do know that when I'm revving higher, getting to highway speeds, for a little longer than normal, my "electrical problem" light comes on and my pressure gauge is all the way up. I'm not a big fan of the digital rpm gauge and pressure gauge but it is quite nifty for the year.
As for what the idle was at before the oil change (stopped at a red light) would be around 650-850 rpm. and the pressure gauge was more in the middle. now it idles more or less at 750-850ish at a red light.
as for the oil, 10w30? owners manual does say 5w30. But it could be worth checking out.

Ive been looking around at automotive places lately looking for a Haynes manual, but usually its my luck that they don't have the one I need.
I looked online at the haynes website and a couple others, and the book is going to cost me roughly $40 because I live in Canada. Which I think is a little ridiculous to pay an extra 20 bucks for shipping a book. (I've ordered big stickers online and only had to pay like a buck or two). So I'll keep looking around in town for this Haynes book.
I was thinking that it could possibly be the computer not reading properly but why all of a sudden when I do an oil change?
I'll also double check the owners manual, and I think I have the original service manual, but I swear I didn't see the oil capacity any where in those books. But I was also kind of in a hurry and didn't spend a lot of time reading. So I'll double check those.

Thanks for the input gents, and I'll make sure to get pictures up asap.

K, so, I took some pictures of the car and took some pictures of what the gauges were reading when it was idling and when I had it revved up.
here they are;
a little above avg. idle, and the pressure should be a notch or two lower.

this is the same, but in metric (psi instead of kpa)

this while i was revving a little

same thing, but psi instead

Thanks for posting the pics. Just my opinion, but 255 PSI seems so high as to be unrealistic. If that were actually the case, I'd think something catastrophic would have occurred by now. My first guess is the oil pressure sending unit is bad, or that system code you noted has something to do with it. Maybe the 'electrical problem' status actually is a response to the high oil pressure value (it's trying to tell you something)?

Thats what I kinda was thinking to. But also, maybe I was thinking into it a little too much. I don't really know. The system diagnostic check the car does every time its started, everything is fine. But again, why all of a sudden as soon as I did an oil change? why didn't it do it before the oil change?

Are you absolutely sure you noticed it reading lower immediately before the change?

I'm 90% certain.
I do know for a fact that, the previous day for sure, it was not doing that because I went to a small city where I grew up for a couple days and it was not like that on the highway.
I'm pretty sure that it started this the day of the oil change though.

What filter did you use? I hope it was not the one you use on the 2.2.

lol. def did not. plus even if i did there is no way in hell it would work. the 2.2 is a cartridge that you place in to where it goes.

also, i took a video on my drive home from work this morning thats about 5 mins long. ill upload it later tonight when im at work. gotta get some sleep first.
is there a site where i can upload videos for free other than youtube?

There are other sites, but I've found YouTube works best. It's gotten incredibly fast recently.

k. ill have to set up an account then. i really didnt want to lol. but hey. gotta get this problem figured out.

I think albertj's suggestion to obtain an oil pressure meter of known accuracy and test - this is the best way to begin solving this problem. Another idea is to just replace the sending unit, if it can be obtained at low cost.

ive got resources, but the resources are an hour or so away. my uncle is a mechanic.

RoughNecks17 wrote:

I am not 100 percent sure what its reading. On my drive home from work in the morning I'll take mental notes. (I work night shift). And I'll get back to ya. But I do know that when I'm revving higher, getting to highway speeds, for a little longer than normal, my "electrical problem" light comes on and my pressure gauge is all the way up. I'm not a big fan of the digital rpm gauge and pressure gauge but it is quite nifty for the year.
As for what the idle was at before the oil change (stopped at a red light) would be around 650-850 rpm. and the pressure gauge was more in the middle. now it idles more or less at 750-850ish at a red light.
as for the oil, 10w30? owners manual does say 5w30. But it could be worth checking out.

Ive been looking around at automotive places lately looking for a Haynes manual, but usually its my luck that they don't have the one I need.
I looked online at the haynes website and a couple others, and the book is going to cost me roughly $40 because I live in Canada. Which I think is a little ridiculous to pay an extra 20 bucks for shipping a book. (I've ordered big stickers online and only had to pay like a buck or two). So I'll keep looking around in town for this Haynes book.
I was thinking that it could possibly be the computer not reading properly but why all of a sudden when I do an oil change?
I'll also double check the owners manual, and I think I have the original service manual, but I swear I didn't see the oil capacity any where in those books. But I was also kind of in a hurry and didn't spend a lot of time reading. So I'll double check those.

Thanks for the input gents, and I'll make sure to get pictures up asap.

The Haynes is worth it at $40 if it means you can quit "chasing your own tail" dealing with this problem.

I hope you get a test OP gauge and take some measurements. if your oil pressure was really that high you'd likely have blown the oil filter can or something by now.

Until you take measurements, good luck and regards to you.

Albertj

Thanks Albertj! Hopefully this weekend ill be getting the OP checked with a tester gauge.

I'm uploading a video right now. I'll post the link soon.

k, so here is the link.

https://www.youtube.com/watch?v=mp9UBAkb1TU



please watch and let me know what you all think.

Raise the car and look everywhere underneath near where you were to do the oil change for something that may now be contacting the wire or pressure sending unit. The pressure sending unit is close to above the oil filter housing IIRC, and you should look all around there for a wire issue.

deekster_caddy wrote:

Raise the car and look everywhere underneath near where you were to do the oil change for something that may now be contacting the wire or pressure sending unit. The pressure sending unit is close to above the oil filter housing IIRC, and you should look all around there for a wire issue.

...and while you are under there wipe off the sender and really look for damage.

Albertj

I'll try my best to get under there this weekend. Thanks for all the help guys! I really do appreciate it.
Also, I just picked up a Haynes book for $24.00(can) at Canadian Tire. Finally found one. Way cheaper than ordering online from their site.