Engine noise sl1

Ive got a 96 SL1 that has 136,000 miles on it. We just got it last month, and it had a rattling noise. I figured it was the timing chain. We got it thru inspection and then it had an episode of running rough at low speeds. I figured the timing chain jumped or something but anyway we went ahead and put the timing kit in.

I replaced the timing chain, along with both guides, both gears and the tensioner. Changed the oil too.

Now, it seems to be running really well again, but the noise is still there. Its sort of a rattle, or a very fast tap. Sort of diesel sounding I guess. The noise is concentrated on the left side as your looking at it under the hood, right where the timing chain runs. I put my ear to the valve cover and it really doesnt seem to be coming from in there.

The noise happens only at idle, with the transmission in drive.
In Neutral, its quiet although if you snap the pedal at idle in neutral, you hear the rattle for a brief instant just when you hit the pedal.

The noise shuts up as soon as you pull off from a stop, and its quiet all throughout the speed ranges. Even if you coast it down to 5 mph in drive, and re-accelerate quickly or slowly its quiet. Or say, the engine is coasting on the hiway, then you put it under load again, there is no transient noise at all. (I say that because Ive had cars with bad valve trains or rod bearing noises that were quiet under load, but you would get a passing tap when the engine was coasting and you started to accelerate again)

Again, it seems to only come at idle in drive. And the speed of the rattle at Idle makes me think that it wouldnt be a rod noise..I dont know. With the way it sounds, I thought it may be an exhaust cover rattling, but I ruled that out. If the sound was coming from the valve cover area that would be one thing, but its definitely from the far side of the engine. I wonder could the water pump make that noise?


Any ideas on what to check next would be greatly appreciated!

Thanks~Neil

Sounds like a bad right side upper motor mount. It's right on top, easily accessible.

Hmmm... I had the upper mount off when I did the timing set...I didnt notice anything weird, but I will give it another look. You know, the lower mount looked kind of crappy... I saw that as I was jacking the motor up a bit to get clearance for the timing job...
Thanks!

sounds like lifter tick.

yes it does, i suggest starting with a oil change, then checking oil pressure and crankshaft endplay

Well, Ive been thru a bunch with the SL1 and I am starting to think its a rod noise. It seems loud at the bottom. I crawled under and had my son start it while I listened.

Its fairly minor as rod knocks go. In that it goes away real quick with a few hundred RPMS above Idle. With that in mind, what are some of your opinions if I were to slap some new bearings in there?
Put it this way, having the crank reground is not an option. If I had the room and the space to work, Id get a motor from the yard I deal with, but....

Im hoping the crank is not too badly damaged.

(I did this with an old Geo I had once, and it lasted a good bit longer)

Yeah yeah its a crappy thing to do, and I know once its slapping, its getting hammered up, but aww hell I dunno.

:screwy:

Hmmm new bearings, some thicker oil, and turn up the radio! YEEEHA!

Countdown to detonation 6 5 4 3 2 1 Ka Blam!

if its rod knock, it should make more noise the higher the rpm. and thicker oil wont exactly help. the thickest the oil it should have is a multi viscosity 10w30. when winter hits drop down to a 5w30 and ive even known guys to use a 0w30 just so it isnt too thick on those really cold days. if you start going thicker, then you can starve the engine of oil and cause worse damage.