On this 1998 V-6 4.3L is it a bad idea to re-torque the timing chain cover bolts? I understand the timing chain cover once taken off is supposed to be replaced with a new one but I haven't taken it off. I'm doing a water pump replacement and noted the entire front from top to bottom of the timing chain cover is covered in oil. It's well known that this vehicle has been leaking oil from somewhere but I never could figure it out. But, now I'm wondering if it's likely to be leaking around the cover and also wondering if this is a common problem.

Since the covers are supposed to be one time use and it appears it is made of composite plastic I wonder if it's a bad idea to check the torque on the bolt and re-torque if loose? This engine probably has 240K miles on it and I know the timing chains and cover were replaced years ago when it only had about 90K miles on it.

There's so much freaking oil plus gunk on the underside of the engine, the sides etc. almost like it's covered in thick mud. I'm going to try and spray it down with heavy duty Gunk gel engine cleaner and hose it down as it seems like it's the only way to figure out where it's leaking. Don't blame me, it's the girlfriends vehicle and I'm just her mechanic, I guess.

Anyhow, before I put in the new oil pump was looking for guidance on if it's a real bad idea to check the torque on the timing chain cover bolts since it got 150k miles on it since the last time the cover was replaced.

 

Yes it is a bad idea. disturbing the timing cover in any way can require crank sensor relearn.

 

Hmm, even turning the bolt 1/4 turn?

How to you perform the crank sensor relearn?...Something only someone with specialized equipment can do?

 

our scanner at work does the CKP relearn but wants you to redline the motor til "fuel cutoff" occurs. so far ive never been successful in having that happen, usually i redline it for a few seconds then say screw it as its usually on high mileage vehicles. usually you can get away with just pulling the battery and let the computer relearn it itself

 

I agree...I'd be uncomfortable red lining a new engine much less this old 1998 Blazer with 240K miles on it.

 

That's not how it works. And yes, you have to have the software/equipment and do the procedure correctly or you just end up repeatedly revving your engine. 4000 rpm is the requirement to trigger the fuel cutoff, but there are a bunch more requirments to meet before you are ready to rev it up. Disconnecting the battery does nothing for crank sensor relearn.

So go ahead and crank away on the timing cover bolts if you like. Just be prepared to do a real crank sensor relearn if you start detecting false misfires. Maybe you will get lucky, maybe you won't. I can't say what will happen for you. All I know is that anytime the timing cover or crank sensor is disturbed, the crank sensor relearn procedure is supposed to be done. Use your own judgement.