I purchased a 94 3500 4x4 for $1100 recently. When I first got it, it would make this same sound for a few seconds after startup and then would go away. Now it is constant. I have had the turbo checked out. Was told it was not the problem. I removed the serpentine belt thinking it may be the vacuum pump. The truck still made the noise. So, where else and what else do I check? The sound seems to be loudest around the airbox area. I replaced the filter. This is a 6.5td truck. The truck has 222,000 miles on it. Doesn't leak any oil or anything. This is my first diesel and I am fairly mechanical. But clueless on this engine. There also seems to be a fair amount of blow by going on. Thanks in advance for your comments.

 

Welcome to DieselBombers. What kind of sound are you hearing? and does it change with RPM of the motor or is it constant?

 

Its almost like a suction noise that lopes with the turning of the engine. It gets louder as the rpms go up. Like the sound when you pull a foot out of the mud. Sort of a hollow thump.

 

A rocker arm that has come loose will make a terrible noise through the turbo, valve covers will have to come off sometimes the rocker arm retainers fail, this sounds like what you are talking about.

 

I'll be sure to check it out. As soon as it stops raining here in mid TN.

 

The rocker retainers are plastic man, stupidest design ever. If rocker slides over just a little, it can be actuating the valve spring retainer and in rare cases, drop the valve. But they normally slide off enough to not actuate valve at all. If it's popping out the intake, it's probably an exhaust rocker. Have also seen lifters come apart with same symptoms. And don't bend the fuel lines to get valve covers off. Good luck!

 

OK. So, it stopped raining and I checked the truck out again today. I used the old garden hose trick to listen to the top of the valve covers.....no noises out of the ordinary. The sound is a definite thump coming from my airbox. That's where it is the loudest.

 

I would start by removing the valve covers and as dieselrick said do not bend the fuel lines or you will most likely be buying a set of 8.