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No mpression on Right side cylendars

7K views 22 replies 7 participants last post by  lmalcom 
#1 ·
Hi, I just bought a 2002 Jeep Liberty with a 3.7 L V6 and the guy I bought it from said it had a broken Camshaft Sprocket Dowel Pin causing the 3 cylinders on the right to not have compression. I pulled the valve cover and cranked the engine with the spark plugs out and sure enough the three cylinders on the left have great compression and the three on the three on the right have 0 compression. Not sure how the dowel pin works as the crank did turn as well as the sprocket and chain. I though it the dowel was broke the cam would not turn. Anyone one have any ideas ? Not sure what causes the dowel to break either, any ideas on that. I have not pulled the cam yet but going to in the next few days. Just hoping to get some insight as to how the dowel and can work before I pull it.
 
#2 ·
Hi, I want to make sure I understand what you wrote. So the right side cam turned when you cranked the engine? This is the side that doesn't have compression?
Did any of the rockers fall off on the right side.

There is a small dowel that helps with the alignment of the cam shaft and then the cam bolt is torqued down to like 90lbs. I doubt the alignment pin broke.

More likely is the center cyl dropped a valve seat and the piston hit the valve and somehow took out the other two cyl. The very worse case scenario is it torqued the pistion bad enough to crack the block. This seems unlikely, I have not yet heard of one of these failing in that manner.
 
#3 ·
Hi, I want to make sure I understand what you wrote. So the right side cam turned when you cranked the engine? This is the side that doesn't have compression?
Did any of the rockers fall off on the right side.

There is a small dowel that helps with the alignment of the cam shaft and then the cam bolt is torqued down to like 90lbs. I doubt the alignment pin broke.

More likely is the center cyl dropped a valve seat and the piston hit the valve and somehow took out the other two cyl. The very worse case scenario is it torqued the pistion bad enough to crack the block. This seems unlikely, I have not yet heard of one of these failing in that manner.
Hi Thanks for the reply - I noticed my grammar in the first post was horrible - I wrote it very quickly before leaving work.

Yes The cam does turn but tonight I got to check it further and I placed the engine on TDC and lined up the timing marks. The V6 mark on the right timing sprocket was well advanced from being in the 12 o'clock position as it should have been. I would say it was more like at the 2 o'clock position. I rechecked the TDC on the timing mark and it was correct so I checked the #1 piston and it was fully extended. I pulled the cam gear and noticed the dowel pin chipped on the end. The dowel pin extended into the pin holding grove of the cam gear but only extended about half the thickness of the gear and it seems to have a chip off one side of the pin. Almost like it jumped the end of the pin one revolution and then caught in the grove again. Sounds totally weird I know.

I did not have time tonight to pull the cam, so I will try to pull it tomorrow. None of the rocker arms have jumped or fell off they are all in place and feel snug. Do you know if the dowel pi should extend to the front face of the gear or even out of the gear?
 
#4 ·
Sorry I realized I did not really answer your questions. The right side (passenger side) is the side that has no compression and the cam on that side turns as the engine turns. All three cylinders on the right side have no compression and all three cylinders and the left side have perfect compression.

When I placed the engine on TDC the right side cam did not line up as it should have. The cam sprocket should have been in a position where the V6 stamp on the sprocket was in the 12 o'clock position. However it was actually at about 2 o'clock. The dowel pin does look damaged but was still in the dowel grove of the cam sprocket.

I am not sure if the timing chain could have jumped - I do not know if that is a common problem with the 3.7 engine. The chain was very tight and the timing chain tensioners seemed to be adjusted correctly as they were holding the chain very snug. I put a wedge in between the tensioners before I pulled the sprocket and I marked the chain and sprocket also. But marking them may not matter if the cam is out of time.

I am not sure if I should just order a new head and cam - and install it or try to figure out what caused the pin to become damaged and figure out how the cam got out of time?
 
#5 ·
You should probably pull the head to make sure there is no damage to the pistons or block before just ordering new parts. If you are lucky, it's just in the head. You can buy a complete head that is reasonable, I believe they run about $500 from Rock Auto or $1100 for a genuine Mopar complete head.
 
#6 ·
If are not going to check and just start the wack a mole approach this will get real expensive. You can test this with a leak down test to know if its valves or rings. But No compression in three on a bank would mean valves are open all the time..Better remove t hat head and be real sure this is not a FUBAR situation.


why buy parts until you know what? That never works most times and new parts on something unknown leads to more broken parts. If the real issue was never fixed.
 
#7 ·
I Agree, you both are correct.

I am,going to have to remove the head and check it out. I am very sure the dowel pin is a big part of the problem. Now I just have to figure out the extent of the damage. I found the below article on line (just click the link) and it describes my damaged dowel pin to a tee. Even the cam sprocket has damage on the back side of it indicating the pin did not hold and the sprocket spun on the cam. Just hope the pistons are ok as getting to the head, valves and cam are not so bad, I am thinking I will have to pull the engine to get to the crank and pistons.
http://www.enginebuildermag.com/2012/04/in-chryslers-3-7l-and-4-7l-engines-as-in-life-timing-is-everything/



 
#8 ·
Hi,
Hoping to get some more advise. I pulled the right side head and all three intake valves have struck the cylinders. I am not sure if the pistons can be buffed and they will be ok, if I can leave them as they are and they will be no real problem? Can they be smoothed out without pulling them out? It is clear the #4 cylinder intake valve lost its seat as you can see daylight under it when it is in the relaxed position. So the head needs a valve job at minimum. I have lots more pics of the head, cam, valves, cylinders etc... if needed.

Any advise would be great.

Thanks
 

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#9 ·
first valve pic looks like the seat dropped on it kinda hard to see well, started the chain reaction. breaking the dowel pin. Block may be ok? but thats a gamble. Messing with those pistons i would think you will do more harm than good. If you remove much that changes there weight. so any attempt to smooth it off would be a bad idea in my book. Hope that no rods bent or bearing issue.
 
#10 ·
I am thinking about replacing the dowel pin, doing a valves job and putting in a new timing kit as the chain tension guides are worn pretty bad and then putting it back together and checking the compression again. I don't really have any experience with valves hitting the pistons so I am not sure if the pistons can take a hit like that or not. At this point does it make since to pull the motor and drop the crank and pistons? The engine turn over by hand vary smoothly but that may not mean anything.
Also while I had the front of the engine open to replace the timing chains and tensioners I was thinking about replacing the oil pump. Do you know if it's possible to replace the pump from just the front or do I have to drop the pan to hold the oil pump pick-up tube?

Hoping to get thoughts on all of it.
 
#11 ·
Both times I had a valve seat drop something hit the piston. Marked it up a bit too. Since the bottom end was recently rebuilt I went ahead and ran it. I have about 25K on it after the first one dropped and it has not caused me an issue.

The 'right' thing to do is pull the motor. A lot depends on your budget and time. If you put it all back together and it runs fine then you save money but the bottom end will eventually wear out. If you put it together and it has an issue then you have to pull the motor which will take time and you will have 'wasted' the time to put the front back on the engine, the hoses, etc.

What are your long term plans for the Jeep?
 
#12 ·
Thanks, I appreciate your reply,

Plan is to keep it for a long time. But the budget is tight for a total rebuild or another block right now. The main driver would be my wife and just around town for the next year or so. I don't have any experience with valves hitting pistons so it is heartening to hear I "might" be able to get by with the pistons for awhile. It only has about 129K on it right now so if I could get it to say about 160K before a total rebuild or a long block that would be great. The body and interior are in really good shape and there is no rust or rot on the frame. I am guessing it was garage kept.

Does yours make a pinging or other noise because of the piston with the ding in it ? Just curious? and do you know if the oil pump can be changed just with access from the front, the Chilton Manual tell me I need to drop the oil pan to remove the oil intake tube. With it being 4 wheel drive I am not up to removing everything required to drop the oil pan right now.
 
#13 ·
That looks so minor Im not sure that I would even worry about it. If the walls look good and youre tight on money personally I wouldnt mind to try it. Maybe keep an eye out for a good low mile engine to swap in if need be. If its only going to be a Jeep to run around town in and not something you plan on taking on big trips, towing, etc, it may be fine like olliehopnoodle has been.

'Typically' a dropped valve seat could mean the engine was overheated. May want to have the heads checked for warping.

Edit: Is that green coolant? These engines came with orange HOAT or G05 coolant.... Could mean that its had overheating issues and they changed out the coolant.
 
#14 ·
Thanks, yes that's green coolant. I will have the head checked for warpage. The cylinder walls look really good, I was happily surprised.
Can I replace the valve seats myself or is that something I need to have a machine shop do? Also not sure if I need to replace the valve guides as I have never done that before either. I have no worries with replacing the valves, valve seals, springs, Lash Adjuster etc... and hand lapping the valves myself. But I have never replaced seats or stem guides so I am not sure if I can do that myself or not. If I can do it myself I would like to try.
 
#15 ·
A head is fairly inexpensive and the right ones come with the cam, valves and lifters installed and usually the new improved valve seats. To me, it's not worth it to rebuild the head myself.

Rock Auto will sell you a complete head for under $400 after return of the core. There are several decent vendors on FleaBay that are also in the $300-$400 range for a complete head.
 
#16 ·
My other advice is to go ahead and swap the other head while you are at it. Make sure the replacement heads have had the valve seats replaced.

I fixed the one head and a few months later the other one dropped a valve seat. I was lucky on both since it barely kissed the piston. If you look through some of the other posts here you will see others are not as lucky.
 
#17 ·
Hi All,
I ordered a new head, It's a "Surefire" head completely rebuilt with cam, valves lifters... etc... complete and ready to install. With the rebates and coupons it came to $325.00 after the $100.00 core charge. I received it the other day and I will install it this weekend. I also picked up a complete new timing kit, as the chain guides were so worn I decided while I have everything apart I should replace that as well.

I appreciate everyone's advise on this and will let you know who it goes after the install.
 
#18 ·
Getting close

Hello All,

I really do appreciate all the help and advise I have received during this project. I bought the Jeep not running so it was a gamble but it is working out nice so far. I got the re-manufactured head installed it and replaced the timing chains and guides. It has good compression now. I will be replacing the intake housing in the next week as the rebuilt head will not have a warranty if I don't. They say there is too much danger of trash entering the head if I do not. I am going to take Ollie's advice and replace the other head, I just need a couple of months for the budget to recover a little from this project.

I have another question I hope you can help with. When I was working on it I noticed the part in the picture below and seems like part of it is missing. Does anybody know what it is?
It appears to have something missing from the bottom of it like a tube or hose attaches to it and also I have to figure out what plugs into it. If anyone know what it is that would be great. It sits on the left side of the engine near the fire wall just behind the fuel rail and behind the intake.
 

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#20 ·
I thought that was what it might be when I looked at your pictures . I went to rock autos website & couldn't find an egr valve listed for an 02 or any part for an 02 that looked like that . Are you sure your engine is original ? I have read about swapping engines & blocking off the egr on engines installed in vehicles that didn't originally have one .

Advance auto lists an egr for an 02 so I'd say that's what it is . Don't know if I overlooked it on rock auto or if they just don't list one .
 
#21 ·
I checked rock auto as well and they do not list one. I went down to NAPA and showed them the picture and they also think it is an EGR valve but they say it is a dealer item only. I will check tonight on e-bay after I have a chance to write down all the part numbers off of it. Also I will need to find the tube that goes to the intake from the EGR valve. I am sure it is an original engine as I matched it up when I did the head and timing kit.
 
#23 ·
Yes - I am in the states (Virginia) bought it from a guy in PA and towed it home. I cannot be sure it is the original engine. I do know the cylinder head and timing kit I bought form it all fit like a glove. Vin # 1J4GL58K92W330125. I would have to find the number stamped on the block to match it up.
 
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