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hello everyone, my Pontiac Aztek with 3.4 liter V6 engine has been recently rebuilt but now has valvetrain tap on cold start up that lasts 3 to 5 minutes before going away. Will this cause any damage to the car or is this normal? valves and lifters have been replaced during rebuild. No noise when cold prior to rebuild, engine originally had rod knock. Many thanks for letting me know.
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First I would consult with the engine rebuilder about the noise and also make sure the engine has the proper spec engine oil in it (5w30.)
The rebuilder said that the noise is from oil taking time to reach the valve train upon cold start but that the lifters have already been replaced. I am not sure what to make of it since this valve train noise did not exist prior to being rebuilt. I already changed the oil filter to an AC Delco since there’s rumors that a fram filter has insufficient anti drainback valve.
That engine should not have noise after cold start up that lasts 3 to 5 minutes.
I assume you’re using 5w30 engine oil? If the noise is the hydraulic lifters after cold start up, they should hold oil (not bleed down) for a long period of time after engine shut down.
In my opinion your engine rebuilder should address this.
Noise after a rebuild shouldn’t be. This is why I recommend replacement over rebuild. Engine rebuilding should be done by people that do it everyday. If not, the slightest mistake can prove costly down the road.
That doesn’t help you however. For that I would say first, make sure you’re using the correct oil. Second, I would take it back to the rebuilder and ask them what they plan to do about it. I would hope they would stand behind their work.
BTW you can’t just replace lifters. You must replace a cam and lifters as a set. If not, it WILL cause issues. So if they only replaced the lifters and not the cam as well, they didn’t do it correctly.
Keep us posted.
My understanding is that it is more important to replace cam and tappets as a set in a flat tappet engine. This particular engine has roller tappets.
I did take the car back to the rebuilder and mentioned the valve train noise but was told it can take time for oil to go up to the valve train or the lifters may be bleeding but there is nothing to do. I can take it back to them in the future if something happens within warranty period. I presume oil is 5w-30 but am not absolutely certain since rebuilder did the break in oil change. Cam bearings, lifters, valves were replaced but not the camshaft itself.
I guess maybe I should start out by doing another oil change to be sure the oil is correct? Maybe try an oil thickener like STP oil additive or LIQUI MOLY?
This is the rebuilders problem and not yours….(really, too many variables to say what could be wrong with it)…
Don’t use a thicker oil… that is only for when masking the death throes of an engine on its last leg or for shady used car dealers who try to mask engine problems to get a car off the lot….. Thicker oil can make things worse… Especially during break in…
-Karl
Alright sounds good, I guess I can change the oil if I get a chance but leave the worrying to the rebuilder hoping that he will stand by his work if something happens in the 2 year warranty period. Would a molybdenum additive like lubri moly have benefits? Just afraid if it’s intermittent issue it may cause problems after 2 years.
[quote=”evergold” post=113172]Alright sounds good, I guess I can change the oil if I get a chance but leave the worrying to the rebuilder hoping that he will stand by his work if something happens in the 2 year warranty period. Would a molybdenum additive like lubri moly have benefits? Just afraid if it’s intermittent issue it may cause problems after 2 years.[/quote]
If the engine had been properly rebuilt it should have no valve train noise for 5 minutes when warming up from cold. It did not have this when new and did not have it before the rebuild. It is up to the engine builder to identify and rectify the fault.
You cannot solve the issue by sticking after market additives in the oil and you may well void your engine warranty if you do. For lubrication, use the best fully synthetic oil you can. This engine should take 5w-30 when new I believe and if so use Mobil 1 — 5w-30 DEXOS 1 (GM spec oil) (or another DEXOS 1 5w-30 spec fully syn oil from another reputable oil company). Just stay away from any after market additives. The oil companies have spent large sums in cash and man hours testing and perfecting their oil additive packages in their various lubrication products and they all advise against compromising or degrading the performance of their oils with needless aftermarket additives.
So I ended up doing an oil change with Valvoline Maxlife 5w-30. Sounds pretty much the same, hopefully it doesn’t get worse. If it does, I guess I can try changing the lifters at a future date. Thank you everyone for all of your sound advice!
As many have stated, this is the rebuilders problem. The engine should NOT make noise after a rebuild. If you have noise, that means somewhere there is excessive clearance. This should have been addressed during the rebuild if it was done properly. Adding thicker oil is a bad idea as that will likely make the problem worse. That said, you might consider contacting the BBB if the shop will not stand behind their work.
[quote=”barneyb” post=113031]My understanding is that it is more important to replace cam and tappets as a set in a flat tappet engine. This particular engine has roller tappets.[/quote]
Still, a cam can get worn and putting new lifters on a worn cam is not going to do any good, even if it is a roller cam. To reuse a worn cam with a rebuild seems counterintuitive to me.
Your experience may be different but this is what I have seen. . .
Certain lots of roller cams get installed OEM in engines or sold as aftermarket with bad metal – probably, not the metal but the heat treatment. I’m not a metallurgist so don’t know. The problem that occurs is spailing of the roller surface and this can occur in a nearly new cam. Other than that, they seem to last forever.
[quote=”barneyb” post=113620]Your experience may be different but this is what I have seen. . .
Certain lots of roller cams get installed OEM in engines or sold as aftermarket with bad metal – probably, not the metal but the heat treatment. I’m not a metallurgist so don’t know. The problem that occurs is spailing of the roller surface and this can occur in a nearly new cam. Other than that, they seem to last forever.[/quote]
Interesting. Thanks for the info.
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