Engine noise after oil change?

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Has anyone ever experienced lower engine noise after an oil change? We changed the oil in my kids 1995 Cherokee with 200k on it and used Mobil1 EP 5w30 and Mobil1 oil filter, he has a vertical filter and we filled it up before installing to prevent dry start.

Previously the motor was whisper quiet and now you can hear rods knocking while the hood is open and if I crawl underneath I can really hear them through the oil pan.

This is not piston slap or lifters it is definitely rods knocking, while not and extreme rod knock it sounds more like they are all loose.

My Suburban does the exact same thing and after a month or so of driving it gradually gets better and stays quiet until the next oil change...[censored]?

Could it be caused by the new oil being thicker than the used oil and not getting between the rods and bearings properly or maybe the old oil pump is having a harder time pumping the new oil? Both vehicles have excellent oil pressure and mine uses a little oil and his uses absolutely none.
 
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PS: No idea what oil was in it previously, we just bought it with 195k on it and the oil looked fresh so I told him to drive for 5k and then we would change the oil.
 
Some engines seem to be noisier with certain oils, my escape is noisier after an oil change and then settles down.

If you are realy sure it has a rod nock and with 200k on the motor I would put some Rotella T 10w-30 or some other thicker heavy duty oil in it.

You say this is the first oil change since buying it, I hope previous owner didnt have something in it to cover up a problem.
 
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Originally Posted By: disturban
PS: No idea what oil was in it previously, we just bought it with 195k on it and the oil looked fresh so I told him to drive for 5k and then we would change the oil.


That doesn't sound good, especially with 195K and an unknown history. Back when I sold cars we had a manager who was not good at checking trades and on more than one occasion he'd take a bad one. When the shop informed him of engine issues, he'd instruct them to get the car ready for the line, or in some cases wholesale it and take the hit. Many times the oil would be changed and Lucas Oil Stabilizer added to quiet the engine down. I recall an Accord he insisted on retailing, and the shop added quite a bit or Lucas OS, a few months later the customer came in complaining of engine noise, he had changed the oil. Thankfully he took an extended warranty and the warranty company covered the engine, others weren't as lucky.

It is possible your engine had some issues and something was added to quiet the engine down just long enough to make the sale, changing the oil drained the "stuff" out. That's one extreme example but it happens often. Hook up a mechanical oil pressure gauge and get hot and cold oil pressure readings at the rpm specd in the shop manual, and compare the hot and cold psi to mfg specs. You can also try a different oil and filter but I don't think it will help much. The oil pressure should point us toward an accurate diagnosis.

Good luck report back!
 
Change the oil filter. It may be defective. If not then the previous owner put in a heavy weight oil or motor honey to quiet it out.
 
This is a good question. I asked this a long time ago and most thought i was full of [censored] and that it was piston slap. My 93 C1500 4.3 does this. After a bit it quiets down. It has 225K miles on it now and it does not seem to be getting worse or better. It has done this for probably 75K miles. My brother jeep 4.0 does the same thing but worse. He has only had it for three years so i cant speak to it being a long term issue or not. In the jeep, he usually runs Pennzoil HM 5w30. The last change we put Rotella 15w40 in it and it really did not change that sound much. Although he says the engine is smoother ect, the start up clunking is still there. In my truck it also don't seem to matter what oil i use. I dont think i tried any 5w30s but 5w40, 15w40,10w40 all have the same sounds and unless its really cold i cant tell much difference between any of them. Maybe the bearings have some slop in them and it just takes a few seconds for them to get hot and expand a little to close the gap (just thinking out loud).
 
Originally Posted By: Radman
Change the oil filter. It may be defective. If not then the previous owner put in a heavy weight oil or motor honey to quiet it out.


Exactly.
 
You can try dropping the pan and just add new con rod bearings.I've done this on an old F-250(I know different vehicle.. different results) to give it a few more years without pulling the engine.
 
I've never EVER known a 4.0L inline six to be "whisper quiet." They don't purr like a kitten, they mutter like a badger.

That said, something that's identifiable as a rod knock isn't usually normal- they do tend to piston slap and to noisy valvetrains, but not usually rod knock.

If the oil pressure is good, I'd just chalk it up to a different oil than the previous owner used and forge ahead. The 4.0 may be noisy, but its tough. 300k miles isn't uncommon, and the 95 model year doesn't have any standout issues so you should be good to go for a long time. If the noise really bothers you, 4.0s respond really well to 4-grade HDEOs like Rotella T6 5w40. You might give that a try.
 
I have to take motor honey or really thick oil out of the equation because the old oil was like water when it came out. I know 4.0's are notorious for lifter noise and that is normal but this motor did not have lifter noise before the oil change nor after it is a different noise deep in the motor like lose rods.

As I stated my Suburban does the exact same thing and it has had nothing but Mobil 1 since it was brand new, after I chance the oil in that the noise is very noticeable if I put my ear in the front wheel well but after a month or so of use it goes away.

Neither of these vehicles are piston slap because piston slap goes away when the motor warms up and the pistons swell, both of these motors still do it after the motor is warmed up.

My wifes truck a 2000 Bravada with a 4.3 does have some piston slap noise and it is more noticeable in the winter but after it warms up goes completely away.

I doubt it is a defective oil filter or the oil pressure would be at 100psi.

Keep the ideas/comments coming I am open to suggestions and would also like to know if this sort of noise has happened to anyone else after an oil change...thanks for the ideas and advice so far you guys rock!
 
I'm in a similar boat as the OP.

After my last oil change(I believe anyway, perhaps just before), I began hearing what sounds like knocking DURING acceleration(while applying throttle) from about 15 mph up to 35-40 MPH or so. Some range like that.

At first it reminded me of CVs starting to make sound, since it was first associated with turning a corner, but it also happens driving straight and seems to make the sound in step/relation to engine RPM at those speeds. I did change the spark plugs at the time of the last oil change so may try to hear which cylinder it's under. Idle seems on the low side(like 400-500), and there is the feel of a stumble or misfire. Though no oil pressure light, if it's a bearing that is spun could that allow for rod knock because of a drop in pressure? Hopefully the car can make it until I can afford to pull the pan and have my mechanic inspect from the bottom end.

PS: No intention of thread hijacking.
 
I had that kind of issues back when I ran Mobil 1 in my chevy truck and is one reason I don't use Mobil anymore. When I switched to Chevron/Havoline the noises were gone. I now run Valvoline with no abnormal noises.

Wayne
 
I agree with lexus114 and Wayne, Mobil 1 5w/30 is way too thin and is causing the noise. Try a heavier weight such as 10w/30 M1. See what the Jeep forum guys with the 4.0's are using in their engines. Verify the oil filter is the correct one and next time use an OEM, but in this case, I don't think the filter is the problem.
 
Do you guys think all the engine noise I am hearing could be because the Mobil 1 EP is a SN rated oil and does not have as much ZDDP as older oils and the 1995 4.0 is a flat tappet camshaft?

I think am going to add some Redline Engine Oil Break-In Additive to boost the ZDDP level and hope that will quiet things down?
 
try some 5w40 or some MaxLife before going to something like RL. It will be a bit cheaper and likely solve your issues.
 
You may have bought a vehicle that had a heavy dose of oil thickener in it to keep it quiet. Not much you can do but go heaver and I would go to a 10w40 Rotella T6 . If it is truly a rod knock then the service life is very questionable in my opinion.
 
Well guess what, I did not want to dump a fresh change of Mobil1 EP so I took the filter off and dumped the oil out of that to make a little room for a bottle of Redline break in oil, I poured in the bottle of Redline to bring the Zinc level up and all the noises are completely gone!

That gives me very bad feelings now towards SN rated oil, that thing sounded like a friggin train wreck with just the Mobil1 in it and now it is smooth and quiet.

I run Amsoil SSO in our 2000 4.3 liter Chevy motor that has a roller cam but now that Amsoil is discontinuing SSO and replacing it with a SN Rated AZO I think my next fill will be 4qts of AZO and a bottle of Redline to bring the Zinc up, I dont care what the [censored] people have to say about how SN rated oil is fine in a roller cam engine I am adding zinc regardless!

Feel free to comment or discuss but my mind is made up and I feel SN rated oil is not a good thing!
 
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