350 chevy question, I know its not a MB
 

My wifes 1995 suburban with 70K miles, started making what appears to be a lifter noise at idle and low RPM, once you rev it up the noise goes away. Changed oil and filter but it did not help. added rislone did not help. any ideas how to get rid of the hydraulic lifter noise, how hard is to replace a lifter. I am more adept at working with OH cam engines.

hard to replace, I would change to synthetic oil REDLINE Brand after running Marvel Mystery oil thru it for a few hundred miles, first try some "Lifter Lube" additive, then Marvel Mystery oil then change oil and filter to REDLINE

sounds like maybe some crud build up....try synthetic for a few changes and see if it goes away. Changing a lifter requires the intake manifold to come off, which as you can tell is not terribly easy.

If it doesn't clear up with synthetic oil THEN I would replace all the lifters.

pull the valve covers and be sure that the return holes for the oil are not all plugged up, this is a real concern. if all is clear, check for a loose rocker by following the firing order 1-8-4-3-6-5-7-2. when the valves are closed you try to turn the pushrod with your fingertips, if you can, tighten the rocker 3/4 turn (i like to use a 1/2 turn) AFTER THE INITIAL FRICTION of the rocker and pushrod, this is the method i have used for years and have never had a problem. if you have to change the lifter it is easy and they are cheap. buy a whole set of lifters and pushrods, it is easier than doing it again. summit racing sells them as a whole set, cheap as well as advance auto parts, i dont like the autozone stuff myself but it is available.

You failed to point out that if adjusting valves statically as you describe that you adjust them while on the heel of the cam.

The easiest and quickest, however the messiest, way to do this is to pull off one valve cover and with the engine idling simply back off each rocker arm nut until it starts clacking then turn it back in 1/2 turn. Don't use a ratchet because it will take longer because of changing ratchet direction. Use a breaker bar, short extension and socket. Then reinstall that valve cover and do it on the other side.

After that change oil hot and often for awhile to get everything cleaned out.

ww.chevyshop.com

maybe some aluminum foil draped below the head would help while doing this. I do remember adjusting lifters like that on the Corvair. The 350 has just GOT to be more fun than doing it on the Corvair. The right side valve cover was parallel with and real close to the muffler. Ouch! :eek:

Haven't done this with ours, but.... why would the intake manifold have to come off?

Steve

The lifters are in the block UNDER the intake manifold....the ride directly on the cam which is dead center in the block. You can replace pushrods without the intake coming off but not the lifters.

http://www.morethanjustpower.com/category.asp?id=6

little holes towards the center are where the 16 lifters fit....the intake manifold covers the lifter galley when its on the engine.

I forgot that this is a roller lifter small block. You need to use some CI4 oil in this engine and change it about every 500 miles or so until the clicking stops.

When you drain the oil, pull the plug while it's hot and let it drain for a long time.

I have an '88 Vette with the same engine and it was clicking when I got it. I only had to do about two hot oil and filter changes with Chevron Delo 400 until the clicking stopped. That was about 50,000 miles ago and it has been fine ever since.

Good luck,

Thanks guys, Larry what is CI4 oil? Also today I drove the burban, towed the boat and the noise kept coming back at idle or close to it. I also noticed the oil pressure went down to 20 on an ocassion at ilde after getting of the freeway. Most of the time the pressure was at 30 to 40 at idle and 60 on the freeway. Not sure if it makes any difference for diagnosing.
I will change the oil tomorrow but I need to understand what CI4 is. :confused:

It's a standard to which oils are tested. It's printed on the bottle. CI is the latest standard I've seen. Basically, good, quality oil.

C indicates the oil spec for diesel engines. Diesel engines require lots of detergent and cleaner additives to deal with soot. These oils are also rated for gas engines and will clean them out very well.

My favorite example is Chevron Delo 400, but equally good for your purpose is Mobil Delvac which can be purchased at Wal Mart.

My guess is that you need to change oil more often.

Keep in mind that it is somewhere between very difficult and impossible, to diagnose noises over the internet, but cleaning out the engine with such oil would be a good first step in fixing the problem.

Please let us know the outcome.

Good luck,

"Gunk" makes an excellent engine flush add to oil allow engine to idle 15 minutes drain oil and remove filter. when adding fresh oil add 1 qt.Marvel Mystery oil in place of 1qt. oil + remainder of fresh oil and filter.
I have done this with 3 cars, Chevy, Volks,BMW and it has worked with each.
This problem usually happens when oil isn't changed often enough when you drain the oil after the flush you will probably see globs of sludge in the oil.
Good luck
Change it hot and change it often is a good rule.

I apologize for disagreeing. Your method will get alot of gunk out of the engine, but is quite harsh. I am inclined to go along with the flushing portion although it is not the approach I would take. What I take issue with is putting MMO in with a fresh oil change. The additive package in modern premium oil is quite good. MMO is an ancient remedy and does not work well with the modern oil additive package and will likely do more harm than good.

The safest way to get an engine flushed and keep it that way is to use one of the oils I indicate or any other CI4 rated oil. Once the engine is cleaned out use your favorite premium oil with ADEQUATE oil change interval.

Thanks for your post and have a great day,

No need to apologize I respect your input and although I am not a fan of flushing engines or of MMO these were extreem cases and the method was reccomended by an automotive engineer who was my neighbor
Flushing engines is risky and you could end up with more problems than you started with.
PS I usually only use MMO in my air tools.