Start up knock goes away.

[froggy47]

I was getting a brief start up knock (like rod or bearing) that went away when I changed oil & filter.

Old oil was 10w30 M1
New oil same
Old filter was ac delco
New was napa/wix

Miles between was about 3000. Change oil light not on yet.

I did run some GM techron top end cleaner thru the tank just before the oil change. This was the strong stuff, not what you buy at Pep Boys. I may have had the noise b4 the treatment.

Garaged w/ start up temps at 45 or 50 this time of year - San Diego.

Question is what do you think the noise was?
Think any damage was done?

Engine is GM LT4 (Vette) with 55k miles. Runs great, burns no oil, maybe a little when I autox it.

Thanks

 

[JHZR2]

Suprising... My 4.3L V6 (chevy) has a short start-up knock when its way below freezing and the truck sits for a week or more. AC Delco (plain ones, not the UPF ones) seem to be the only filters to prevent this from happening! Mine uses a PF52.

JMH

 

[froggy47]

Anyone else? What kind of temporary start up engine noise would go away with an oil change. TIA

 

[ZR2RANDO]

New filter allowing more cold start flow would make a pretty good difference...sounds like you found your new favorite filter?

 

[SWS]

This is interesting. Have you considered any other effects? For example, were you driving it really hard, then garaged it, and it knocked on the next start-up? Then you drove it easy, changed the oil and it did not knock? In this scenario, could spark advance, injector heat-soak, a slightly sticking valve, etc cause a knock that goes away? Also, could you have a tiny bit of piston slap with this engine?

I am no mechanic, but I am interested in transient effects like this, and will be interested in you continued findings. The best answer is usually the simplest answer, and indeed your oil filter swap-out was a wise action!

 

[Virtuoso]

If that's the only thing you changed, perhaps the Delco had a leaky anti-drain-back valve. I've had a Motorcraft do this to me; probably happens to all brands sometime.

 

[wymi]

I've tried a dozen different filter/oil combinations in my noisey at start-up 01 3.1L Malibu. The best so far is Havoline 5w30 GF-4 and the standard white Purolater filter, I get very quiet starts with this combo and the Purolater filter seems to keep the oil cleaner than any other filter I've tried.