I just bought a 98 z28. When it warms up the oil pressure drops to zero and I get the top end chatter. I figured it was the pickup tube. I was right but it's also the worst sludged engine I've ever seen. I pulled the valve covers and couldn't even see the head bolts. I vacuumed out all I could, put it back together and get the same problem. Is there a way to save it without rebuilding?

 

How long did it take for the sludge to return?
AutoRX is a great but slow cleaner.

 

There are a couple of engine cleaners on the market that work to various degrees. Seafoam, Chevron, B12 Chemtool, Marvel Mystery Oil, etc.

I would buy 3-4 bottles of whatever, and a couple of cases of the cheapest 5W-30 motor oil you can get. Put in a bottle of cleaner and run it at a fast idle until it gets up to operating temp. Let it sit for a short while, and drain while it's still warm. Repeat the process a few times, using a new filter every time.

That will cost <$100, and may or may not work. But it's worth a try. If your pressure is still low, pull the engine and strip it down.

Remember that sludge like that can sometimes be caused by repeated overheating. Be sure and check piston ring lands.

 

I know Amsoil carries an engine flush that I have used before and it cleans the engine real good- Made a noticeable improvement on my ball-less dodge neon that was my winter car for awhile.

you could try that along with a sea foaming. Just don't try and overkill it because it is so bad.

Unsludging the engine could lead to other problems, but I personally would try to get the sludge out and see what happens from there...

Then just make sure you use a quality oil from here on out with regular changes.

I've been doing tons of research on oils for the past few months and I've started to pull a bunch of my findings together, so fwiw, you can reference the below links

Oil specs definitions

5W30 oil comparison - synthetic and non synthetic oils

I have to add more oils to that list, and I want to do it for every weight of oil, but atleast it is a start and can give you a sense of what is good without having to wade through hours of reading...

 

I would pull the motor and do a tear down and block cleaning. The bearing are more than likely bad if oil pressure dropped anywhere near zero

 

It actually did better today. It idled for 15 mins at 50 psi then dropped to 40. I ran it down the road and it never got below 15. I have already pulled the pan and changed the pickup tube and pan gasket. I found some stuff from the UK that is supposed to be the best stuff in the world for dissolving hard carbon deposits. It's called Flushing Oil Concentrate. I think I might just save this motor. The dumbass I bought it from only changed the oil 2 or 3 times in 150k miles. He needs to be in jail. Thanks for the feedback.

 

Good to hear- I mean if there is damage done already to the motor, I don't think you are going to get much worse assuming you dont let it fully blow or overheat.

You'll know if she starts to spin a bearing, if it does, shut it off, tow it and rebuilt it. As long as it doesnt throw a rod through the block / head...you mine as well see if you can save it.

 

I had very good luck using Rislone to remove sludge. I started with 1/2 qt in 5qts of oil then 2k later add the other 1/2 qt of Rislone and run it to 5k then dump it out. After 2 changes doing this the engine was trouble free again, lifters quiet etc. The 1st oil change after using Rislone the oil was VERY DIRTY. 2nd change it was better, 3rd it was clean like it should be.