Timing Problems, No Compression

[aparker]

Alright guys I can really use some advice. My 94 path's water pump went out, so i got a new one and set off to replace it. Unfortunatly I didnt find this website or do enough research until it was too late. I didnt mark the timing belt or pay much attention to the position of the pulleys and now it seems I've fouled out a couple of the heads. The truck will start but runs very rough and only starts with the throttle held wide open. A friend recommended I check the compression so i purchased a compression guage and I'm showing 0 pressure on 2 of the valves. I have no idea where to go from here. Can anyone recommend steps on how to remove the heads or advice on what to do and DEFINITLY on what not to do. I really dont want to tear anything else up, this little water pump leak has already cost me alot of time and aggrevation. Thank you for any and all advice

[Precise1]

Ok, please don't run it any more. Damage may have been done but lets not add insult to injury.

 

What needs to be done is the timing belt set correctly and then the heads addressed. I'm not sure if it should all be done at once, but that is where I am leaning. There is a How To pinned in the Garage section for the timing belt, and let me if I can find a thread about the heads...

 

B

[jj big shoe]

If you haven't read already, it's an interference engine which means the valves and piston use the same space in the cylinder at different times. Sounds like a couple valves smacked the pistons and are now bent and don't seal properly. Sorry to say, but if that's the case you'll have to remove the heads and replace the bent valves or swap the heads with a different set. Hopefully the pistons aren't scarred up too bad.

On the up side, used heads aren't hard to come by and are relatively cheap. Plus you don't have to pull the engine for this repair.

Grab a Chilton's manual. It'll have all the assembly/disassembly, torque specs, bolt loosening/tightening sequence, etc for a job like this.

[unccpathfinder]

Ok, please don't run it any more. Damage may have been done but lets not add insult to injury.

 

not necessarily true...if theres not valve tap it's already bent them and they will no longer hit...after breakikng a TB and bending 3 valves I drove my truck on 4 cylinders before rebuilding the heads...

 

I would assume that you have a pretty decent mechanical aptitude since you did the waterpump...rebuilding heads isnt a big deal...I'd go get a 10MM alan socket, torque wrecnh, top end engine rebuild kit and 12 new valves...

 

you gotta pull the intake, valve covers, rockerslifters, then pull the head bolts and bolt that holds the head on after of course removing the exhaust...once you have the heads off you can inspect the pistons for cracks...I had 2 dimples from 2 of the valves and the 3rd valve barley kissed the piston and didnt leave a mark.

 

you will need a valve spring compressor and a magnet to pull compress the springs and pull the retainer collars...once you have the old valves out you can serach for bent ones but i'd just replace them all...you'll need to get a valve lapper and lap the valves in and then you can remove and install new valve seals, the springs and valve retainers...while hte valves are out and the heads completely torn down i'd clean them up good before lapping in the new valves and assembling them...to clean off the old head gaskets don't use any metallic pads use a 3M abrasive pad...I've carefully used a razor blade to scrape some of the gasket off but you want to be extremely careful with the aluminum heads

 

theres an FSM on here available somewhere...it gives you torque procedrues as well as assembly and disassembly instructions...find it and read it and use it as a reference...to locate the crankshaft pulley at TDC put cylinder #1 flush with the block before installing the passenger side head (i know most of the VG30 blocks are missing the timing alignment mark on the block) i used a punch to mark my engines that i've had apart and werent marked for future references. cylinder #1 is the fwd most on the passenger side...I hope that helps out some

 

Top end "rebuild kit":

 

 

bent valves (2nd from the right is a straight valve):

Edited February 21, 2010 by unccpathfinder

[wris]

I hope aparker has resolved the cylinder head problem, and I don't have additional advice on the topic, but this is the latest post I could find on timing questions. my 95 xe appeared to have jumped a cog. 160,000 miles of history and I have no knowledge of any maintenence that has been performed, so decided to replace the belt. To make a long story short,you don't necessairly need to remove the drive sprocket from the crankshaft to replace the belt, and we almost didn't. something just didn't look quite right so we took it off. the woodruff key which locates the sprocket on the crank was almost completely sheared off. one more backfire would likely have spelled the end of the motor. I'm shure others have seen this, but in 45 years of wrenching,or is it wenching?, it's my first. Using a new key,We filled the damaged key slot with liquid steel, put all the parts back where they belonged, and I think it's saved. so,words to the wise,Look very carefully at your parts. Don't let anyone tell you "it's probably ok".

[Precise1]

Thanks for the heads up, I know of 2 or 3 other people who have had this problem. It is rare, but it happens...

 

B

[ahardb0dy]

this happened to me also on the 94 I just bought, first thing I would suggest to check is to pull all the spark plugs, when I pulled mine the first 5 looked ok but the 6th one was definitely hit, I couldn't understand how the plug would have gotten hit as I didn't think the piston could go up that high, it wasn't until I spoke to my mechanic who told me the piston hit the valve which hit the plug, makes sense. Anyway, I would look at all the plugs, if you find one hit you bent a valve than follow the previous advice.