Tap While Engine and Air Temp. is Cold

[SR77]

I have a 1996 Explorer V8 5.0 AWD. I got the truck late last winter and noticed that in the cold weather and when the engine is cold, there is a tapping noise from under the hood that i can not pin point. Then during this summer when the outside temp. warmed up the noise went away completely until now because it is starting to get cold out in the morning again. I hear the tapping when the engine is cold and ususally is most noticable as I am on the gas. As the engine warms up the tap gets quieter until the engine is at operating temp. and then the tap is gone. At first i thought that it was something in the head or a lifter and that oil was not getting to it fast enough, But I use 5w30 and the tap is noticeable until operating temp. which is long after oil has made its way through the engine. Any help is appreciated, thanks

 

[huskyfan23]

Could be an exhaust leak or rocker tap. I can't remember which, but (I believe exhaust leak) tapping is louder when cold. Does it tap faster as you accelerate? I've got exhaust leaks where my header flanges meet the y-pipe, but hear them all year round because of the size.

 

[james t]

It will be the infamous passenger side exhaust manifold leak. All of the 5 liter explorers do it. It starts out ticking only when cold, because the leak is so small that when the engine heats up it will mostly seal off. Eventually it will leak all the time. You simply need new manifold gaskets.

 

[chico]

I have a 91 and it does the same thing. I've narrowed it down to that the sound is the lifter priming back up and then the noise goes away. It seems to take longer as it gets colder outside. Hopefully this will help. chico

 

[Bronco638]

Sounds like a sticky lifter to me. But, I wouldn't discount the possibility of the exhaust manifold leak. However, even in warm weather the exhaust leak would be present (tick when cold) with a cold engine. That has me thinking it's most likely the lifter.

 

[SR77]

thanks for the replys. Two things, If it was a sticky lifter was does the sound only happenin the winter and while the engine is cold. If a lifter is sticking wouln't you still hear it at operating temp. Is there a solution to this without opening the engine? Two, If it is the common passenger exhaust manifold, would the air temps. in the spring/summer be enough to keep this sealed and thats why it only is heard in the winter while the engine is cold?

 

[Glacier991]

I'm guessing hydraulic lifters myself.... but don't discount other theories

 

[james t]

If its a sticking lifter (its not, its the exhaust manifold on the passenger side ) then you can do this. Next time you get ready to change your oil, add a quart of transmission fluid to the engine oil and drive it for a few days. Then change the oil. If the lifter is sticking than the detergents in the ATF fluid will clean the valley out and it will usually become unstuck.

I still say its a manifold leak.... and even though you never indicated i bet its coming from the passenger side. Every 5 liter Explorer ever made that has the stock tubular manifolds develops this type of leak.

 

[Bronco638]

The hydraulic lifter works kind of like a shock absorber between the cam shaft and push rod. If the lifter is "stuck" it doesn't absorb any "shock" from the push rod (caused by the valve spring). When the lifter warms up, it becomes free and can absorb the shock caused by the valve spring closing the valve. There are other types of engine flushes (Rislone, Marvel Mystery Oil, etc.) that are supposed to free stuck lifters. But, as I mentioned before, as well as james t, you need to investigate the exhaust manifold, too.

 

[expobronc]

yup manifold leak, mine does it, i just havent been able to get the bolts off to fix it yet. Mine goes away after it warms up too