No compression in two middle cylinders

[l7inthegst]

So i did a compression test and cylinder 1 and 4 are good, but 2 and 3 wouldnt even move the needle( Gauge starts at 25 pounds), but when i was doing the test on 2 and 3 there was a weird noise like something was hitting the part i thread into where the spark plugs go. I recently had a new headgasket put on around 3500 miles. I dont have my head off yet but could this hopefully be a stuck valve or somthing in the head maybe?

 

[95blackGsTurbo]

Were all the plugs out and the throttle open during the test? If so then you have a few possibilites. Headgasket blown between cylinder 2 and 3, bent valves, or timing off.

 

[l7inthegst]

ya all the plugs were out, i do think it could be timing actually because i just checked out the 2 notches on the cam gears and one was like 1 1/4 of an inch away from where they both are supposed to meet, and the other notch was like 5-6 inches away from where they meet, so i think that could probably be it, if that is it what kind of damage can i expect, and what that have caused that noise i heard when testing cylinders 2 and 3?

 

[rlacasse1]

Well if the timing is that bad then you can expect bent valves. And valves hitting pistons could have caused that noise.

 

[l7inthegst]

So when i take the head off i will be able to see if there is bent valves? I have never taken a head off before so thats why i ask. Also does this maybe sound like a symptom of something wrong in my block?

 

[rlacasse1]

No Your block will prbably be ok if the valves touched the pistons.

When you get the head out pull the cams out that way all the valves will be closed. Then spray carb cleaner into all of the intake and exhuast ports. Do them one at a time. And as you do them look at the corresponding valve and see if the cleaner comes dumping out. If it does then that valve is either not seating correctly or bent to hell.

 

[haswesley]

To determine if your valves are bent, simply take your valve cover off and see if any of the valve springs are still compressed when the cam lobe is up.

 

[95blackGsTurbo]

In extreme cases that will work but if they just touched and aren't completely sealing then the spring will look normal to the naked eye. Either way the head has to be removed. Reset the timing and recheck compression.

 

[BogusSVO]

if you have a bad slipped time belt.. once you have the head off you will see bent valves...

look in here and you will see what I mean...
http://www.dsmtuners.com/forums/newbie-forum/341218-how-change-valve-guides-4g63t-head.html

with some luck, what you may have heard was the air passing from one cylinder to the other over the HG

if you have the head surfaced, make sure the shop dose NOT belt surface the head!!
http://www.dsmtuners.com/forums/cyl...0613-why-not-let-your-head-belt-surfaced.html

what gasket did you use when it was replaced? also whas the head surfaced at that time?

if you pull the head you may want to do this oil mod....
http://www.dsmtuners.com/forums/newbie-forum/341028-4g63t-head-oil-port-mod.html

 

[donniekak]

Most of the time the bottom end will be ok. But sometime the piston will smash, and the ring will be pinched in the groove. I just did a skipped timing/ bent valve engine for someone. Not only was one piston totally wasted, because the valve head broke off, but the head was scrap metal, and on another cylinder the upper bearing shell was cracked in half in the rod, that was a first for me. I've heard of bearing fracture, but never saw it first hand.

 

[l7inthegst]

Well the head is almost off just got to get the two pulleys off and then moment of truth, I appreciate all of the advice and suggestions from all of you guys thanks. But I will keep you guys informed on how everything. Also anyone got any tips and tricks on how to easily get the water pump pulley and crank pulley off easier?

 

[rlacasse1]

With the crank pulley just unbolt the four little bolts that surround the center one and the pulley will come off. You will just have to try and hold the water pump pulley still and use a wrench. I can usualy wedge a screw driver between the bolts to hold it still with. Usually works for me.

 

[95blackGsTurbo]

Well the head is almost off just got to get the two pulleys off and then moment of truth, I appreciate all of the advice and suggestions from all of you guys thanks. But I will keep you guys informed on how everything. Also anyone got any tips and tricks on how to easily get the water pump pulley and crank pulley off easier?

Leave the belts on before loosening the bolts.

 

[rlacasse1]

+2 on leaving the belts on. Although that seems to work for people it has never worked for me, but try it.

 

[l7inthegst]

Well i got the head off and the head gasket was bad, like it looked the a fire cracker went off between the two middle cylinders, no damage to head or block though PHEW!!!!

 

[BogusSVO]

good now check the head for warp....

http://www.dsmtuners.com/forums/articles-engine-fuel/341627-how-check-head-warp.html
of you can fit .003 feeler gauge anyehre under the bar.. have the head surfaced properly.

if the head needs surfaced.. do not let the machine shop use a Belt surfacer...
http://www.dsmtuners.com/forums/cyl...0613-why-not-let-your-head-belt-surfaced.html

the surface should like this...
http://www.dsmtuners.com/forums/new...face-4g63t-cylinder-head-mls-head-gasket.html


and measure the head thickness at 4 points around the head to determin thickness
new thickness of a 4g head is 5.200 according to AERA, and has a min thickness of 5.185 if your head is thinner than 5.185 get a thicker head gasket to bing it back up to a min of 4.185

 

[dsm_92_fwd]

Too bad this thread ended i was anxious to hear the outcome

He told the outcome... Blown headgasket between 2-3, reading helps

 

[mattasi]

, got to read the whole thing man!