Oil pump and oil pressure

[mrd05d]

I was thinking about my oil pressure problem today and thought of the following, I would like to know if it is correct:

So the oil pump is set to pump the oil and it will have a maximum psi rating.
As the oil pump wears the max psi decreases. Thus on cold start instead of 60 psi you would get say 40 because the max it could push would be 40. Then as you rev you would not see much difference because again the pump only can pump 40. When the car heats the oil thins and the pump would then create less pressure because of the thinned oil.

Does this seem correct or am i way off base here?

[techsan23]

Re: Oil pump and oil pressure

It is not actually an oil pump, but a set of 2 gears with one inside the other that creates a vacuum pulling/pushing the oil through the block. The higher the rpm, the faster the gears are spinning. Alot of the time oil pressure problems are the result of improper tolerances on the crank or cam bearings unfortunately.

[cam98aro]

Re: Oil pump and oil pressure

It is not actually an oil pump, but a set of 2 gears with one inside the other that creates a vacuum pulling/pushing the oil through the block. The higher the rpm, the faster the gears are spinning. Alot of the time oil pressure problems are the result of improper tolerances on the crank or cam bearings unfortunately.

i agree

but you can try to replace the oil pump and see if it helps

you wouldnt think that 0.005" of wear on the bearings could cause the oil pressure to be 20+PSI lower, but it def. can

[nascar24jd]

Re: Oil pump and oil pressure

Ok, I have been reading through all three of your threads related to the problem with your car.

#1. Your compression numbers don't look bad. Yes, 2 of the numbers are slightly lower, but not that bad.

#2. Have you found out if you are in fact leaking coolant yet? Or, if it is not leaking, are you losing coolant? Is the level continuously dropping?

#3. What weight oil are you using in your engine? If you have the start of a true oiling issue, step up to a heavier weight oil. If you are using 5w30, change it and use 10w40 to see if your pressure goes up.

[Rangersltw]

Re: Oil pump and oil pressure

To increase an oils weight wouldn't he want to go up to 5w40 or 10w40? The second number is the viscosity of the oil at operating temperature. The first number tells you what the lowest temp it can operate in.

I was having oil pressure issues before and as a temporary fix before i rebuild, i switched to 10w40 mobile one full synthetic. It was a combination of a faulty pressure sending unit and just having an already lower psi. Switching to the 10w40 gave me some extra psi so my stinking check gauges light wouldnt come on. At idle I am around 20-30, and driving im around 40ish(at operating temp) cold start up is 60psi.

According to my GM service manual the 3.8 should have 60psi at 2000rpms idk about the 3.4. Double check your oil pressure with a mechanical gauge to make sure your gauge or sending unit aren't bad. I've also heard that the gauge readings arent always very accurate.

[nascar24jd]

Re: Oil pump and oil pressure

Yes, I made a typo, meant to type 10w40. But actually, the oil numbers are not related to temperature that they can operate in, they mean the following:

Oil Viscosity
The viscosity of multi-weight motor oil is specified using two numbers. The first number is the viscosity when the oil is cold. This is followed by the letter W (which stands for winter, not weight), which is followed by the number that indicates the viscosity when the oil is at operating temperature. The higher the number the thicker the oil.

So, after fixing my typo, change to 10w40, if that doesn't do it, then 20w50, if that doesn't help, time for new engine...

[Rangersltw]

Re: Oil pump and oil pressure

I guess I was a little bit off on that one, haha. Thanks for clarifying.

[mrd05d]

Re: Oil pump and oil pressure

Ok, I have been reading through all three of your threads related to the problem with your car.

#1. Your compression numbers don't look bad. Yes, 2 of the numbers are slightly lower, but not that bad.

#2. Have you found out if you are in fact leaking coolant yet? Or, if it is not leaking, are you losing coolant? Is the level continuously dropping?

#3. What weight oil are you using in your engine? If you have the start of a true oiling issue, step up to a heavier weight oil. If you are using 5w30, change it and use 10w40 to see if your pressure goes up.

I am loosing coolant but cant tell if what leaks is coolant or condensation after its been running.

Right now i am using 10w30 and planned on switching to 20w50 with Lucas but was going to wait until since i didn't know if i was going to drop the pan or something this week and i just changed the oil again yesterday.

[mrd05d]

Re: Oil pump and oil pressure

Okay so I wish to check the oil pump. What do i need (gaskets and all) and how hard/time consuming is it to do? Any special tips or directions? How will i know if the pump is bad and needs replaced.

[techsan23]

Re: Oil pump and oil pressure

Plan on replacing it; its only about $40 and you will have everything apart anyways. Your going to have to pull the alternator, tensioner bracket, harmonic balancer and timing cover. You will probably just need a timing cover gasket, thread sealant and some rtv unless you see something else while your in there. The cover has 4 bolts going thru the oil pan. Hardest part will prob be removing the balancer. It can all be done in a day. You check the oil gear drive with a feeler gauge around the outside circumference. I dont have the tolerances in front of me. Good time to check the timing chain for slack.

[mrd05d]

Re: Oil pump and oil pressure

Plan on replacing it; its only about $40 and you will have everything apart anyways. Your going to have to pull the alternator, tensioner bracket, harmonic balancer and timing cover. You will probably just need a timing cover gasket, thread sealant and some rtv unless you see something else while your in there. The cover has 4 bolts going thru the oil pan. Hardest part will prob be removing the balancer. It can all be done in a day. You check the oil gear drive with a feeler gauge around the outside circumference. I dont have the tolerances in front of me. Good time to check the timing chain for slack.

Thanks for the reply I guess i just buy the rebuild kit then... What should the timing belt look like? just tight?

[nascar24jd]

Re: Oil pump and oil pressure

Thanks for the reply I guess i just buy the rebuild kit then... What should the timing belt look like? just tight?

It is a timing chain, not a timing belt. There should not be much slack in the chain at all. If the chain feels loose, then replace it while you are in there.

[mrd05d]

Re: Oil pump and oil pressure

It is a timing chain, not a timing belt. There should not be much slack in the chain at all. If the chain feels loose, then replace it while you are in there.

Sorry was thinking about something else i meant timing chain...

[mrd05d]

Re: Oil pump and oil pressure

Plan on replacing it; its only about $40 and you will have everything apart anyways. Your going to have to pull the alternator, tensioner bracket, harmonic balancer and timing cover. You will probably just need a timing cover gasket, thread sealant and some rtv unless you see something else while your in there. The cover has 4 bolts going thru the oil pan. Hardest part will prob be removing the balancer. It can all be done in a day. You check the oil gear drive with a feeler gauge around the outside circumference. I dont have the tolerances in front of me. Good time to check the timing chain for slack.

I read somewhere that i will have to pull water pump as well? Then i assume i need the new water pump gasket?

[techsan23]

Re: Oil pump and oil pressure

i assume i need the new water pump gasket?

you are correct.