QuestionQUESTION: 1995 pontiac Grand Am, 3.1 liter auto, 150,000 miles. Just started suddenly. loud tapping in lifter area, worse than diesel. Oil light (not low light) illuminated. I figure it's the oil pump, but wondering if there is something specific about this engine I need to know that might add input to the diagnosis
ANSWER: Hi
If it was me, I would preform a manual check of the oil pressure.
Does it go away at higher rpm's?
You could just have trash blocking the sump screen. However it may be more. You may have contaminated oil.
When was your last oil service? Weight of oil? To me, a sudden lifter problem is more unlikely tahn likely, especially with 150k.
Granted it may just be the pump. As a mechanic, though I would want to look at ALL the possibilities it could be.
It could be faulty cam bearings, they cause low pressure.
I would hook a manual oil pressure gauge to the system and see what your actual oil pressure is.
Please feel free to follow post.
Good Luck
Just advice from experience.
Pawl
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QUESTION: Thanks for the response. Looks like the oil pump probably is not the problem. I pulled it, and it pumps oil very well in the basin of oil when I turn the oil pump driveshaft by hand. The pump shaft came out with the oil pump, and I have a friend who thinks the shaft should have been retained in the engine. Can you verify that? By the way, it didn't go away with higher RPM's, although I didn't give it much of a chance since I was afraid of blowing the motor. I thought about the pressure check, but went ahead and started since I had the low pressure light and the associated noises with low oil pressure.
But there was more to the problem than I realized last night when this problem showed up. Apparently, something failed catastrophically, as there is oil down the entire underside of the car. I still haven't figured out exactly where the oil came from, since there is no obvious oil origination point.
As far as service is concerned, I keep the oil changed every 3,000 on this car because of the high mileage and the overall reputation of these "disposable" cars. I use 5W-30, as per the engine, but I guess I might need to go up a level.
If you have a minute, give me a quick overview of what you mean by sudden lifter problem, so I can use your advice as a starting point.
Again, thanks for the advice. I do understand that this is just advice, not gospel. I treat this as buds' giving each other ideas.
ANSWER: Hi
Sudden lifter problems, I mean like they ok one minute, and they just collapse, sudden like.
With the symptoms you are giving me, I would first find the source of the oil leak. I think that will be a GREAT starting point.
Actually, other than the Lower intake gaskets leaking on these engines, they are VERY reliable, in my opinion.
The oil pump drive shaft dont matter one way or the other, as long as you stab it all the way in the drive. In as much as I have changed hundreds of the Drive assy O rings on the top by the intake I know the shaft comes out sometimes either way.
With a full oil pan, does it still make noise? Is there plenty of oil for it to pick up and maintain?
Keep in touch.
Also, please, I am not saying it is not just the lifters...They do have a history of being a weak point of the engine.
Pawl
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QUESTION: Talk to me about collapsed lifters. What is the remedy for this problem.
I think I've found the oil leak. Weird though...the starter was soaked, so I went up from there. The side of the engine and the head were dry, but the oil pressure switch was soaked, so I guess it failed?!?! Not something I've seem before.
I'm going to put it back together with a new switch and the old pump and see how it does.
Thanks for the patience...I only have a couple of hours each night, and have worked this weekend, hence my lack of diligence. I'll let you know. Thanks, Jim
AnswerHi
Oil is fed through the oil gallerys bfro the pump.
The lifters have an inlet port on the side, which allows the pressurized oil to "pump" them up, hence taking out the 'slack' AKA valve lash. Most hydralic lifters have a check valve so oil does not leak out over time. This makes the oil present in the lifter so all we need to do is pressurize the oiling system and oil start to flow through the lifters. (It flows up the hollow pushrod and this is how the head/valvetrain gets its oil.) The oil not leaking out keeps the unpressurized lifter "pumped up". This is why like on really cold mornings, or maybe if there is very thick oil, or low or no oil, the lifters "tap" or "Rattle" until pressurized oil can "pump" them up again, and the noise gets eliminated.
In some instances, the lifter "collapses". The check valve may fail, sticking open all the time. There may be a blockage in the oil inlet port from the gallery. For whatever reason, the oil pressure just cannot pump the lifter up. This is a collapsed lifter.
(FYI, GM now Electronically purposley "holds" lifters open hydraulicly, and shuts off fuel, to allow for the Displacement on Demand [DOD] system in their vehicles for fuel economy)
Anyways to replace them on your vehicle, the intake manifold MUST be removed and the lifters replaced from the top.
If you need them I would shop around and get good ones like from maybe an engine rebuilding shop, or if your local parts store carries good name bran lifters. I also would change all 12.
IF you go to do this yourself, which I WOULD not recommend unless you have done engine work before, is to MARK THE PUSH RODS. They are VERY close to the same length. If they get put in the wrong place, serious engine damage WILL occur.
Hope this helps
Pawl
