1999 4.8 Broken rod - piston hitting valve - HELP...

[kahjdh]

Since you have the intake off did you remove the valley pan and look at the lifters? Off on a limb here but what if a lifter collapsed and the runner filled up then pumped back up and hydro-locked the cyclinder? Explains the noise from the loose pushrod when it blew up.

[easygoin43]

I did not remove the valley pan, From what I can see the cam looks ok and nothing caused me to be concerned in there- I did pull 2 lifters on this side (1 in this cyl. and 1 in the next) they appeared ok.
I never had a pushrod noise it was a broke Connecting rod that was banging on the oil splash pan.
I received new piston last nite and now rings not in till Monday so this weekend I do some more investigative work. I need to get it back together before I go crazy thinking about it.. LOL

Question: would you guys use the head bolts over? remember 171K on it, but be honest I will replace if you think I should. It is only $27.00 for bolts - but this little project is nikle/dime to death- I have not done engine work in prob. 15-20yrs and man have the gasket $$ gone thru the roof.

If you think it would help I can take a few close up pics of head gaskets both sides?
I'll try to clean gunk out of intake this weekend too.

Thanks
Chris

[2000CAYukon]

I would not reuse the head bolts. Think about how many heat cycles they have gone thru. Plus they might be torque to yield bolts so don't take a chance for $27.

//2000CAYukon

[CJ0717]

Use new bolts.

Do not use the old head bolts. Since about 1993 or 94 GM as well as the rest have gotten away from a torque only strategy and went to a torque then an angle. i.e. torque to 85 ft lbs then turn the bolt an additional 90 degrees. This ensures that the bolt stretch is attained to get the proper clamp load. Clamp load is what holds the parts together. Torque only can be tricky due to all the other factors like thread integrity, debris on the threads and any other cause of friction which will show up as torque and yield inconsistant resultant clamp loads.

The bolts are designed to stretch.

Whenever I do a head gasket job I always use new bolts irregardless of how old they are. It doesn't cost that much more to make sure it holds correctly. Last thing I want to do is to do the job over a second time.

[easygoin43]

ok new head bolts it is..
I'll let you know if I find anymore interesting fact today on the old parts.
Thanks
Chris

[j cAT]

Originally Posted by easygoin43

ok new head bolts it is..
I'll let you know if I find anymore interesting fact today on the old parts.
Thanks
Chris

the GM repair manual states on head removal must use new bolts..
make sure you follow the thread cleaning of the block threads and use the proper thread material / torque proceedures...

[easygoin43]

Saturday I got her back together - Checked the old coil and it was firing, all new plugs and new injector in that cylinder. Primed the fuel system few times and she fired right up. No miss, no Lights, no noises.. Runs Great..
I will get a few miles on it and change the oil and filter a few times.
Coolant is staying right up there and temp. is perfect.
Crossing my fingers that she keeps running this good.
I did pull the #4 cyl. plug and couple others to check it and seemed to be burning the same as others. I will pull it again every 10-20 miles or so to keep an eye on it.
Thanks a lot for everyones help on this one- Guess I got lucky SO FAR..
Never did really figure out the cause of the broken rod.
Chris