Hi all, 1997 3500 with 44,000 miles and no mods. I have a tapping noise coming from the engine bay and it's kind of intermittent. Like "Tap Tap Tap " than say a 2 or 3 second pause and tap again.

I've read on here after doing a search to check the overflow valve. Does it make a noise like that when going out? It kind of sounds like a lifter noise but not consistent at all, has like a rhythm to it. Truck is running fine with no differences anywhere else.

Thanks,
Ryan

 

could be a loose valve or the piston lift pumps are known to do that tap tap tap nothing sound. use a hose and hold one end at the LP and other end on your ear see if its the pump ,if it is no worry

 

Thanks Rebal. I just went out to try that and before I started the truck I found the lift pump and pushed the primer button, than started it and it wouldn't make the noise. After 5 minutes running I "think" I heard it again but very subtle this time. I only had a very thin hose to listen with but I didn't hear anything from the pump.

I think if it's valves it would be all the time, but maybe not. One more note, I changed the fuel filter about a month ago. I never bled the system or cracked the banjo fitting on top of the canister. I read some guys had knocking noises from air in the fuel lines. Is that possibly my noise?

Thanks again for the reply,
Ryan

 

its posable but I bet its just the lp

 

If it is the LP when will I know it's really on its way out? Can it go for awhile making a noise like this?

I also have had the ticking noise you hear between the cab and bed, and have read that is also the LP. Are the two noises related at all do you think?

I might change the overflow valve because it's cheap and easy and I don't have any gauges. Thanks for the replies.

 

I dont know about the clicking by the bed but we have a 97 thats been clicking for years now and it pulls a trailer everyday

 

I wouldn't change the OV unless you have a pressure reading to verify it is bad. With that few miles, and having the original, it might be a better unit than the one you replace it with. At the very minimum, hang onto the old OV.......

And Brownie ticked at the LP from the day I bought her, still does with the new owner, never dropped pressure.

 

Pat thanks for the reply.

I'm thinking it's something else now that I listen more. I've been having problems with my belts getting eaten up, replaced the tensioner but it's starting to do it again. So my thoughts are either I got a bad new tensioner or my ac compressor is bad. It sounds like my tapping noise is coming from the area of the tensioner and compressor. I hear it best with the hood down and ear in front of the grill. Do you think either of those things could make a noise like that? When I use my AC the compressor also clicks on and off rapidly, like every 20 seconds. Don't know if that is a sign of a worn compressor.

Also, it's not really a ticking noise I hear, it's like a marble rolling in a can, and it's definitely not consistent. I think I'll just hold onto this new overflow valve and keep it until I really need it.

 

a/c comps last a long time ,It might be your tensioner I have had a few bad out of the box,if the inside edge if the belt is getting eat up its probably the tensioner

 

I just went out and removed my belt from the Ac compressor and spun it by hand. Not loose but there is a slight grinding bearing noise, similar to the noise I hear but much less noticeable. I know the truck has very low miles, but the guy I bought it from only drove to work in it very local, like a half a mile, and I bet he never used the AC. I've had it for a year and have used the AC frequently.

Is it possible to just idle the truck with no belt to see if the noise goes away?

Thanks again guys.

 

ya you can idle for a min. with no belt wont hurt a thing but make sure the noise you hear from the A/C comp is not the mag clutch dragging

 

Well I removed the belt and the noise is still there, so that rules out tensioner, compressor, or fan pulley.

I'm guessing it must be the LP and I'll just have to keep my eye on it, looks like a lot of them make noise and still last.

I did install towing mirrors today though so it's not a complete loss!

Thanks again for all the help guys.

 

My 97 had an intermittent tapping noise that appeared to come from the bell housing area. It disappeared when a set of Bosch 275 injectors were installed. In fact, several weird noises disappeared, the engine runs smoother than it did when I bought the truck, and it now goes over steep inclines in a single bound.

If your AC is cycling frequently you might consider having the refrigerant level checked.

 

Thanks Dram. My ac blows cool, but not cold. Think I'll charge it up this weekend.

What if I run some injector cleaner through my system? I never did it and since I bought the truck last year with 36,000 miles and I put on 8,000 this year maybe it can use it.

Anyone have recommendations on a safe cleaner to use?
Thanks

 

I use lucas but power service from wally world is good too wont hurt a thing.
and you will love the tow mirrors