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98 GMC may have sludge


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christalcat
New User

Mar 8, 2009, 5:07 AM

Post #1 of 4 (1410 views)
98 GMC may have sludge Sign In

I have a 98 GMC 3500 7.4 L which I use as a canteen truck
oil is changed every 3000 miles although I may have gone over a few times
recently I have been hearing a clicking noise but not all the time
how worried should I be ?
what can be done ?
I have had issues with poor coolant circulation and apparent evaporation of coolant in the cap
radiator and heater core are less than 1 year old but there appears to be gunk in the radiator
thanks for your help!!


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Mar 8, 2009, 5:29 AM

Post #2 of 4 (1409 views)
Re: 98 GMC may have sludge Sign In

The type use - perhaps low mile, lots of idling and short trip may be stressing your oil and I suggest changing more often and using synthetics.

Cooling system: These came with Dexcool when new that didn't turn out so well in hindsight. What kind of goo are you noticing now? If just at the radiator cap - clean it and see what returns if anything.

I suggest if on Dexcool now even just a year out changing to regular non color differentiated extended life coolant - properly mixed AFTER a good flush (whole cooling system) again. Heater performance can be a good clue as to gunk build up. It it's fading it may be catching debris/goo that just might mostly flush out,

T



christalcat
New User

Mar 8, 2009, 5:35 AM

Post #3 of 4 (1407 views)
Re: 98 GMC may have sludge Sign In

Thank you Tom for your reply. By the way this truck has 145000 miles. Do you think that by changing the oil more often that will make the clicking / sludge problem go away?
thanks again


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Mar 8, 2009, 5:50 AM

Post #4 of 4 (1402 views)
Re: 98 GMC may have sludge Sign In

Pay attention to the clicking. I don't know what is causing it and it may not be an oil issue at all - can't say from here. For oil sludge detection - pulling a valve cover is a giveaway as to how well it's doing with the current routine of changes and oil type used. Dipstick may show something or sometimes underside of an oil fill cap gives some clues.

Sludge in oil slowly builds and items needing it slowly get less and sometimes real local friction heat will make oil sticky like a varnish. Plain oil changing can reverse that to some degree. Additives are in new oil and I shy away from magic tricks for that - keeping in mind we don't know this is an issue at all!

The reason for suggesting synthetics as they plain tolerate heat better than conventionals so the chance of sludge is reduced.

If ticking noise is better or worse when cold or warm it may be solved with choosing different oil and changes - again can't say for sure. If you are worried enough about the noise please do have it diagnosed in person and pick a plan from there,

T







 
 
 






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