98 Silhouette new gaskets, now knocking??

[Colbysmommy1231]

We got a 98 Silhouette and it needed new intake and head gaskets, we replaced them, and now it is making a loud knocking noise when in idle and when you step on the gas. The van ran perfectly fine when we brought it home ( we had to frive it home knowing the head gaskets and stuff were already blown) it was only making a light ticking noise like it needed an oil change. We got it home and parked it until we could get it fixed.. I did move it a couple of times, and it STILL did not make the noise it is making now. It sounded smooth and still with only the light ticking. My friend came yesterday and replaced the gaskets, and when taking it for a quick drive around the block, I noticed the knocking. He said that is is just that the oil is too thin and to put some STP in it. My neighbor came and looked at it and he said it sounds like a cylinder or rod? And that we need a new engine.. Any suggestions???? Any help would be greatly appreciated!

[94 Jimmy]

Did you change the oil when you got done with the heads. It's possible that water got by the head gaskets and into the crankcase. You might have 10 or more quarts of goo down there that the crankshaft and connecting rods are banging into. This will definently cause problems.
If you have coolent in the oil it will reduce the lubricating properties of the oil to nil and carry any crud in the cooling system into the tight little areas between the hard steel and soft bearings where it will grind groves in the bearings.
To do, RIGHT NOW.
Check the oil level on the dip stick. If there is any milky sludge on the dipstick, that's water, and that's bad. Immediately drain the oil and replace it and the filter. Use any 30 weight oil, and cheap filter, start and warm the engine, shut it down and change the oil and filter again. Use a good filter and oil. If you have many miles on the engine a single 20 or 30 weight oil will give some cushon on the worn bearings other wise a good 10-30 will do.
G.M. means noisy valve lifters. It seems to be one of those things you see in certain engines. Valve lifters ride on the cam shaft and work through various parts to open the intake and exhaust valves at the right time. The lifter is a cylinder and piston which fits together and fills with engine oil, as the valve train wears the piston simply moves out a little to take up the slack. If you have any water in the oil it will froth and fill the lifter with some air bubbles. The air will compress unlike oil and will allow slop in the valve line which will cause a clicking (or banging depending on how bad) noise as the valve opens. Again change the oil to get any water out.
I've saved the worst for last. Were you very, very careful when you replaced the pushrods. The intake and exhaust pushrods are different lengths. If you got any of them wrong, you will drive the valve down into the piston, destroying the valve and probably the piston. I double, and triple checked mine and still worried until I started the engine the first time. If you got one reversed the engine is probably toast. Sorry to say but valves do not like hitting pistons.
If it's just the water thing, make sure you change the O2 Sensor. Sorry it a bear to get at, it should be done every time you tear into the engine, perhaps a mechanic with a lift can get at it from below. The antifreeze destroys the sensor and dosen't do much good to the Cat either.
Good luck, let us know what you find.
94

[Colbysmommy1231]

Thanks 94 Jimmy. Yes, we changed the oil and filter as soon as we got done replacing the gaskets, and when I checked the oil, it was very thin, but clear (meaning no signs of water or antifreeze). I called my friend (who worked on it) and he said that the knocking was just that the oil was too thin and to put STP in it. Well, we had 3 other people tell us about the pushrods, and I told him this, and he said that it would be making a higher pitched ticking noise. He came back over today and took everything apart again, and he said that it seems like the engine isn't getting enough oil. So, he lubed it, and changed the oil and filter again. I just went and started it, and it is still making the same exact noise that it was! I am at my wits end about this! I had one person tell me that it could be that the oil pump is gunked with all of the sludge and that- that could be causing the engine to nor be getting enough oil, could this be? As you said in your post before, about the pushrods and everything, and that blowing the enigine, would it still be running if the engine was blown? It starts and runs fine except the knocking noise. Since he replaced the gaskets, I have only driven it maybe 2 miles total, because I was afraid I would do more damage since the knocking noise. Any more suggestions?

[94 Jimmy]

It's hard to tell what's the problem. Everything in an engine can click, bang, thud, or make noise of some kind. A lot of diagnosing the problem is what kind of sound is it making and how often.
Something connected to the crankshaft will make a noise each engine revolution, click, click, click. If it's connected to the cam shaft, like the lifters it will make a noise every other revolution, since the cam turns at half the engine speed, so it's click,......click, .. Then there's the low oil pressure which dosen't allow the lifters to pump up which makes a constant clatter.
As I said in my previous reply, the lifters are made up of a piston inside of a cylinder which is filled by the engine with oil. The piston is free to expand to make up for any wear in the valve line so that there are no valve adjustments necessary for the life of the engine. If however, a piece of dirt gets into the lifter fill hole so that the cylinder can't fill, the piston will have some free play to allow it to bang against the cam or pushrod. On some engines a lifter will drain down overnight so that it causes a tick....tick when you first start the engine in the morning. Mine has done this for its 165000 mi life, no problem 30 sec of ticking and it runs like a top from then on.
Get a flashlight and watch the lower (crankshaft) pulley on the engine, while listening to the noise. Does it occure each revolution or every other, you don't have to be too accurate but you should be able to tell the frequency. Needless to say keep away from the moving parts if you like all of your body parts attached instead of in a jar on the mantle.
If you think it could be a single lifter, it is probably not oil pressure related, but rather a piece of debris preventing the lifter from pumping up. You can try an agressive engine flush to try to desolve some of the dirt to allow it to move along and get caught in the oil filter, it's worth a try in any case. My local Car Quest sells a really stinky stuff that your suppose to be able to put in your gas tank to clean injectors, in the oil to flush out crud from your rings and lifters ect. Again it's worth a try.
Let us know.
94