not quite knocking from the rear valve cover

[hawkeye18]

My engine is making a noise very similar to when you stop pedaling a bicycle when it's moving, only deeper and louder. I have isolated the noise to the cyl. 1 area. This noise ONLY occurs between 1500 and 2000 RPM. Once I hit 2000 RPM, it switches off... literally like somebody flipped a switch. It only does it when the engine is good 'n warm. Doesn't do it on the way to work (11 miles) but it does it on the way back. Very odd.

Question is... I have to take this thing from here to Virginia Beach (~200 miles) on sunday. Do you think the engine'll explode on the way there? There are no symptoms of rod knock. Oil pressure is good (I checked) and the noise is very definitely coming from the valve cover area... and I can hit junkyards a'plenty once I'm down there to replace whatever I need.

Opinions pleeze... I'm thinking something is dicked up with the cams/buckets (ate a shim?). It doesn't matter; I have a new set of heads/cams/shims ready to go onto the car once I get a set of head gaskets... so if the rear head goes kablooey I'm not too worried about it.

 

[93rev2sev]

remove accessory belts and re-test.

 

[SHO GoDz 89]

Doubt your engine will blow up. Doesn't sound like a huge issue, probably valve tick? Check your lash. Also, could you determine if it is coming from under the timing covers or not? Screw driver to the ear would help (or stethoscope)

 

[hawkeye18]

It's definitely not coming from the timing belt. I spent many a minute with a hueg screwdriver and it's not coming from either the p/s pump, front valve cover, or timing belt. It's quite a bit quieter even in the cyl. 3 area. It's definitely centered right over cyl. 1. I ran it with both the acc. belt and the timing belt cover off, and while there is a little deflection while the belt is running (~1/2"), it's nowhere near enough to be slapping the cover.

What precisely is valve tick? I've never really understood the concept...

 

[pccorrig1]

Does it sound like this?

http://www.youtube.com/watch?v=WVzy84q9n9Y

On mine it was caused by worn out timing CHAIN tensioners. They are under the cam covers of each cylinder bank on the drivers side of the engine.

 

[hawkeye18]

It does sound like that, but the noise is very definitely coming from cylinder 1, on the timing belt side. Eh... as long as it's not the rods, f#*% it. I doubt it'll blow up. Like I said I have a new set of heads/cams/valves/shims/buckets/the works ready to go in as soon as I get a set of head gaskets. And a spare day or two.

 

[Mr Anonymous]

This noise ONLY occurs between 1500 and 2000 RPM.

Every time I have had a car with a noise that only appears in that RPM range it's either a failing timing belt tensioner, or crank cancer.

 

[hawkeye18]

Ok, riddle me this then. I have my tranny set to downshift from 3-2 at 28mph which kicks the engine up to about 2Krpm (cos it shifts a little late depending on how fast I'm stopping). This is when it does it the worst, right when the engine kicks into braking mode. This would obviously mean that the crank is putting opposite rotational torque on the belt for a little while, right? Do you think that would have anything to do with it?

After a while, when it gets good 'n warm, it'll do it regardless of what my inputs are within that RPM range.

Another question: I ran the engine with the timing belt off for a little while and noticed about .5-.75" of total deflection during operation. Is that normal?

 

[93rev2sev]

Timing belt tensioner. It should not deflect during operation.

 

[Mr Anonymous]

I ran the engine with the timing belt COVER? off for a little while and noticed about .5-.75" of total deflection during operation. Is that normal?

I'm presuming you meant the upper timing cover...

Timing belt tensioner. It should not deflect during operation.

Correct, at least not enough to be detectable by the human eye.

 

[hawkeye18]

well ****. Anybody got a tensioner? lol although I suppose I should make sure it's not crank cancer first...

Is there any way to repair a tensioner that anybody knows of?