I have had for a couple of months an on going kluncking noise at start up. The symptoms are after the truck sits for several hours and is started, a loud klunck thunking noise is present, but not at every start up, noise goes away as oil pressure builds and at some start ups it seems it takes longer for oil pressure to come up.

Has anyone experienced any noise from a 7.3 IDI oil pump?

Thanks

 

I have a knock/thump at cold start sometimes but thought it was an injector or something...it goes away after a few moments...interested if it is the oil pump too.

 

Well if you are making oil pressure slowly, maybe the oil pickup is starting to get clogged up. which could cause damage to the oil pump. But the noise your hearing could be worn mian bearings or connecting rod bearings from a lack of oil pressure.

 

Slow is a relative term. When I say slow I mean within a couple of seconds the pump gets primed and I have normal pressure, based on the idiot gauge right away. The other day I was leaving a camp over nighter and in a crowded parking lot fired her up and I had a few folks jump out of the way from the noise, That one seemed to have lasted longer. Once the pump got it's prime it was gone. so within those first couple to few seconds the first times you hear it the noise can make you jump out of your skin,

My next course is to try an oil additive to see if that quiets things down and helps the pump keep a prime or stay lubed.

Any other suggestions would be greatly appreciated.
Thanks

 

well for a start we can start with basics, check the oil level. and have you tried to hook a master gauge up to verify that the oil pressure is low at start up. does the truck smoke alot at start up?

 

I topped the oil off the other day and I need to get some decent gauges, it's a hard sell to the wife. No smoke at start up. The only smoke is when I have to get on it up a hill or pulling a trailer.

 

Speaking of additives...when I first heard the "knock" thump I got some stuff called "valve medic" from advanced auto and it actually worked, for about a week...

Maybe try valve medic...

maybe also add some kind of "slick50" type stuff or seafoam,etc and see if it makes any difference?

BTW...my oil pressure thing never even goes to the "L", much less near the middle...I saw it go over the L once when it was cold outside...

 

well the no smoke rules out the possibility of a glow plug being bad and not having the cylinder warmed up. and the valves would not make a thunk sound. they would be more of a quiet ticking. what brand and weight of oil are you running in your truck?

 

I was thinking the same about about the lifters and valves, more of a tapping noise.

The truck has had Rotella 15/40 run through it since brand new.

I had just put some lucas in today. we'll see if that does anything.

A rod knock?..... I've always known them to get worst when under a load

 

I say lifters...my 91 does the same thing

 

So have you done anything about it or just living with it.

 

I just live with it...Honestly im just waitin for it to blow...I boost the s*** out of it and let EGTs get super high and she won't give lol it's been knocking like that from about 180k miles....now has 220k last 20k has been rough on 'er! If my valley pan ever leaks again then I'll replace the lifters...but that sounds like a lot of work

 

A lot of work was my thought. We'll see if the Lucas does any good, if it's pump, lifter or what not oil seems to clear it up. I just never heard a lifter this loud, but I never heard a lifter go out in a diesel before.

 

You dont want a lifter to go out. It will wipe out your cam shaft and spit needel bearings through out your engine.

 

Yes I agree.

I started up the truck this morn. and had a dull thud instead of the hard knock, so maybe the Lucas is doing some good.

Finally got a chance to run some questions by my mechanic and he says the noise is not from the oil pump, most likely from the main, but it is prob. due to the fact it takes the oil pump 2-5 seconds to start building pressure and causing excessive wear on it.