fpapp

1999 Chevy Suburban (1500) (2wd) 5.7 V-8(256,000 miles) Oil Pressure guage shows high upon start up and remains high for the first 5 minutes of driving then drops to normal, Additionally the engine knocks and chatters during this time. After the first 5/10 minutes everything returns to normal, and noises go away and runs like a dream. Any suggestions?
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shamrock246

I have about the same miles on my 97 i hear some piston slap that goes away after about a minuet and then i here a little bit of valve train noise but after about 3mins i hear nothing the engine is smooth during all this,is the engine smooth or is it shaking?im using 10w-40 in mine fully warmed up i the summer i have about 30psi @600 rpm and about 60 when i first start up

Perry_Amo

How offten do you change your oil and filter? I get the same issue but I run full gauge at startup and it evens out at around 40 after a few min and the knocking goes away. After I change my oil and filter it does not have the problem and no knocking, but after about 1,000 miles it will start doing it again and I change the oil and filter to resolve it again. What I was told by a mechanic was that it needed a new engine, that things where just to far worn out and that the oil was sludgy, he cut my oil filter and showed me the sludge build up in it, and also after a new motor to also do the radiator at the same time cause the sludge will be in the oil lines that run through it and would get into the new engine. This was back in January, it is now Oct and I still have not put a new motor in it and just change my oil and filter every 1,000 miles to help with the issue. Not sure how long this will last thought.

shamrock246

I change it once a year before boat towing season(MAY)i only put about 2,000 miles a year on it,i use Mobil 1 10w-40 high milage i tried some rislone a couple of weeks ago and it reduced the lifter noise and for how long it did it for and my oil got darker afterwards,might change it soon and use some gunk 10min motor flush and see what happens i saw a light coating of sludge on this motor when i did the intake manifold gaskets,i used Pensoil 10w-40 the one thats supposed to clean up to 40% of the sludge in the first oil change i think it did something i cut the filter open and found sludge in the filter

73shark

Welcome to the forum.

First, when he said replace the radiator, was he referring to an external oil cooler? Or does the radiator contain an oil cooler in addition to the tranny cooler?

Might try running a straight weight oil such as a 30 or 40.

Perry_Amo

My oil lines also run through the radiator, there is a separate tans cooler on the front side of the radiator. That is why if you have sludge build up in your engine you need to at least flush it out of the radiator oil lines as well...other wise the sludge is just going to get back into the engine.

73shark

That's interesting. I've never seen an engine oil cooler in the radiator. Live and learn.