P38 with machine gun sound at 2,200 revs

amongstit said:

My 1998 P38 diesel auto is making a machine gun sound from what seems the top of the engine as it goes through the rev range at around 2,200 revs.
It's without vibration and disappears with a change of gear or when I reach around 2,700 revs.
If I very gently go through the rev range the noise isn't there but even with a normal driving pace on the road the noise is present.
I've revved it hard with my head under the bonnet and no noise,I'm hoping it's a common loose part in the bay but as yet I can't find anything loose though I've only had a quick scan,any advice would be greatly appreciated.

Click to expand...

Hi.i had the same issue on my p38 but it's a v8.the prob was tht the fan was hitting the rad coz the rad mounts were loose thus causing the rad 2 shift inside out and touching the fan.i suspected tht this is ur case coz ur rad was changed,when ur truck is at idle,hold ur rad from the top plastic and push it in and out,if there is sufficient play in it it will hit the fan.mine as said was a v8 duno abt diesel.good luck.

Not had chance to look at any of the areas mentioned but I did take it out for a 80 mile run last night after adding 2 litres of water to the cooling system.
After the first 20 miles the noise had totally disappeared along with the dash creaking I've been getting(I'm aware this had nothing to do with topping up the cooling system),at the end of the run I popped into a local field to test my low gears and suspension,everything was fine so I left the field and dropped it back to the normal ride height(solid line setting on dash) and once again the machine gun/chatter noise appeared but not as loud and still certainly from the top of the engine,the dash creaking was as loud as before if not louder,so I ask again,any ideas?

I think this may be the least of my worries though as I think I'm losing water,last night I added 2 litres and had to get rid of an air lock,I can see it's had a new rad so I'm hoping the tosser who fitted it didn't bleed the system of air,it wouldn't surprise me,yesterday I found a rad pipe that was rubbing on the side of the rocker so the last owner or his backwards mechanic had rubbed grease around it to delay the friction from damaging the pipe,I've since loosely zip tied it with success

mcapinha said:

Problems with a worn/loose chain in the transfer case are almost always described as a "machine gun sound". I came into this thread expecting this to be the case but I don't see anyone pointing to it?

Click to expand...

Yes true, but a machine gun sound from under the floor not from the engine bay. Unless the OP has an hearing problem.