compression Test Results

[FuddyMucker]

Hi Guys

After having done all of the basic service stuff, the VX is still running rough.
Although there is no oil in the water or water in the oil I have done a compression test and it goes something like this

1 = 190
2 = 170
3 = 180
4 = 0
5 = 170
6 = 165

I all happy with all the cylinders results (after 260000 km) except for cylinder #4.
I am trying to think of a reason why I would get this sort of result as it is not the standard results of a blown head gasket.
Thinking maybe stuck valve or broken con-rod or maybe even a hole in the piston.
Any other ideas??

[crotchrocket]

Of all of those, i'd say sticky valve although im not sure if that applies, Do we have hydraulic lifters????? Normal valves????? cant remember on the 3.2?

The con rod would have made a mess inside and the hole in the piston would surely blow crap out the spark plug hole when opened wouldn't it?


I take it knackered piston rings wouldn't give a reading of '0' would they??

Looks like head off for a better look inside

[FuddyMucker]

I think your right, for knackered piston rings not to register anything they would both need to be completely gone.

I'm hoping on the valve because so far that seems to be the easiest to fix, if (as you pointed out) there not hydraulic.

[FuddyMucker]

OK I am quite sure I have found the problem!

http://i47.photobucket.com/albums/f182/FuddyMucker/VX/IMAG0149.jpg

http://i47.photobucket.com/albums/f182/FuddyMucker/VX/IMAG0148.jpg

http://i47.photobucket.com/albums/f182/FuddyMucker/VX/IMAG0153.jpg

Because of this I have now ordered a new head gasket and am trying to get a new valve.

Anyone else had this issue?

[Ldub]

OK I am quite sure I have found the problem!

Yep, that looks like it might cause a reduction in compression...:smilewink

Anyone else had this issue?

That's a first in my memory, don't remember seeing that before.

Good luck with getting it back together soon...:luck:

[VX crazy]

Oh my, that sucks....makes me want to run out and get a compression test....that looks like *** with all that carbon buildup!

[Cobrajet]

How do the piston and cylinder bore look? I once ingested a carburetor bolt (anybody remember those?) down my intake and it ended up notching the top of piston, which eventually burned a hole through the piston. I was able to get away with just a new piston on that cylinder because it didn't scar the cylinder wall. I later bored the engine .030 over and fitted balanced piston/rod assemblies.

[VX KAT]

OK, translation please....what's happened there? I'm always curious....:?:

[Moncha]

Actually for 260k km that looks pretty clean! Not very much carbon build up at all, at least on the head.

Depending on what the valve seat shows, I'd say bad valve. If the seat has a chinger in it, then maybe foreign object. Maybe a chunk of carbon. What's the top of the pistons/cylinder look like? Was the ring intact?

After looking at it more; looks like incomplete burn or oil build up.

What did the spark plug look like? was the electrode intact?

What's that cylinder look like?

Did the gasket survive enough to take pics?

[FuddyMucker]

Spark plug was intact and looked ok
Piston rings look ok and have standard slack.
Head Gasket shows no sign of leaking (but I will replace it anyway).

Thank goodness the chip of valve got blown out of the engine and didn't fall back in to the cylinder (the cylinder wall also looks good for 260,000)

http://i47.photobucket.com/albums/f182/FuddyMucker/VX/IMAG0158.jpg

http://i47.photobucket.com/albums/f182/FuddyMucker/VX/IMAG0159.jpg

http://i47.photobucket.com/albums/f182/FuddyMucker/VX/IMAG0164.jpg

[VX crazy]

can you give us a tad more info, what made you get the compression test done, how was it running etc....

[FuddyMucker]

It was running Rough, it wouldn't idle but would hunt between 550 to 1200 rpm
noticable lack of power (more so at low revs).
This was one of the last checks I did after replacing the sparkplugs, checking the MAP sensor, checking the MAF sensor, checking each coil pack, checking the fuel pressure in the line, looking into the EGR system, checking for water in the oil, checking for oil in the water ect...
Put it this way, it didn't seem like a compression issue but I was running out of other things it could be.

[Moncha]

Hate to be a PITA, what's the valve seat look like.. I see a small nick out of the valve just to the right of the chunked out part but, it's not part of the seat. This one doesn't look like it's been seating for a bit as there is quite a bit of crap built up. That could just be from trying to run it while diagnosing but.... I'm tempted to say from the looks of the valve and the lack of other damage any where else, the valve just failed. Maybe to much valve slap from mal-adjustment but, that should show in the seat. What does the stem head look like?

[FuddyMucker]

Sorry for the quality of these snaps, Im at work at the moment and only have the camera on my phone.

Here are some snaps of the valve seat after I cleaned the carbon off (typing with dirty hands, eerrr)

http://i47.photobucket.com/albums/f182/FuddyMucker/IMAG0166.jpg


http://i47.photobucket.com/albums/f182/FuddyMucker/IMAG0167.jpg


Seat looks good to me
What do you think?

[VX crazy]

It was running Rough, it wouldn't idle but would hunt between 550 to 1200 rpm
noticable lack of power (more so at low revs).
This was one of the last checks I did after replacing the sparkplugs, checking the MAP sensor, checking the MAF sensor, checking each coil pack, checking the fuel pressure in the line, looking into the EGR system, checking for water in the oil, checking for oil in the water ect...
Put it this way, it didn't seem like a compression issue but I was running out of other things it could be.

Great.....mine rough idles sometimes...not all the time, today was just perfect running......I need to clean my EGR too.

[Moncha]

Make sure to have a good head shop look at it but it looks like the valve just failed.. Everything else looks to good to say that it was anything else. Keep cleaning and checking though, you never know what you'll find under the carbon.

Lisa, don't worry about this, you would have major problems rather than just idling rough sometimes. This is probably a one in a million and after 161,000 miles (260000km) may just be a failure on a 3.2l engine.

[FuddyMucker]

Lisa I Agree with Moncha, your problem sounds like it is nothing to serious, maybe just a new set of plugs are needed or a coil pack is starting to fail (which is easy to fix in the US because spares are easier to get than here in the UK).
If it was a valve, you wouldn't have days where it ran well ;)

I have had to order an exhaust valve from a Vaxhall Frontera because they don't list anything for a Vehicross because it is classed as a Gray Import.

[Ldub]

You've probably already thought of it but...:_wrench:

Remember to get new head bolts...:yesgray:

http://cgi.ebay.com/99-01-3-5-L-Isuzu-Vehicross-V6-6VE1-Cylinder-Head-Bolts_W0QQitemZ260530791467QQcmdZViewItemQQptZMoto rs_Car_Truck_Parts_Accessories?hash=item3ca8d8642b

http://cgi.ebay.com/99-01-ISUZU-VEHICROSS-3-5L-24V-CYLINDER-HEAD-BOLTS-6VE1_W0QQitemZ400017005940QQcmdZViewItemQQptZMotor s_Car_Truck_Parts_Accessories?hash=item5d22df1d74

[FuddyMucker]

Yes I had thought of doing the head bolts but am having issues finding a UK supplier, I have ordered a new head gasket set to rebuild it with but wasn't sure how important it was to change the head bolts. Its something I have never done before, do these ones stretch?

[FuddyMucker]

Here are some better photos of that failed valve (for all those members who are as curious as me ;) )


http://i47.photobucket.com/albums/f182/FuddyMucker/VX/IMG_3082.jpg

http://i47.photobucket.com/albums/f182/FuddyMucker/VX/IMG_3081.jpg

http://i47.photobucket.com/albums/f182/FuddyMucker/VX/IMG_3074.jpg

http://i47.photobucket.com/albums/f182/FuddyMucker/VX/IMG_3080.jpg

http://i47.photobucket.com/albums/f182/FuddyMucker/VX/IMG_3078.jpg

Looks to me like it had been fractured for a while before it came completely off, what do you guys think?

[FuddyMucker]

Has anyone else done a head gasket before and not replaced the head bolts?
Has anyone else in the UK managed to get hold of head bolts?

[Moncha]

Looks like that valve had been burnt for a while, then the failure. Probably from mal-adjustment.
My brother-in-law is coming over tonight and I'll show him these. He, as well as the rest of the side of his (Ms Moncha's) family owned and operated an automotive machine shop for decades. The bro-in-law specialized in valve trains. He may have a good idea of what happened.

Always, replace the head bolts as under torque, they do stretch and you want to do it right after going through all of this.

[FuddyMucker]

:) Thanks Moncha, I would be intressted in your brother-in-laws opinion :)

[Moncha]

Me too! I wanna see if I remember what I learned :)

[Moncha]

Ok, the pro spoke.

Burnt valve is the cause the of the valve failure. The valve burnt most likely from an overheating situation. Any over heating that you remember?

That valve burnt due to the center cylinder being hottest due to design. When it got hot, It at sometime has caused it to hang open thus allowing hot gasses to blow by the valve making the valve head get hot and "Crystalize" then snap!

You can see that the head gasket was allowing gasses blow from cylinder to cylinder (Red Circles) but, not necessarily coolant because it wasn't at the water jackets.

The yellow circle shows a or the location that may have been the hot spot for over heating. That would be on the intake side and it would have been the part that got the hottest.

Advice, Take both heads off have both redone professionally, new valves, new guides, new seats, re-surface, and new gaskets along with new head bolts. If you do that then you won't be doing this again in another 1000 or so miles if you don't.

[newthings]

As an ex-failure analysis and electron microfractographer (SEM and TEM), I can definitely say it is broken. Nice last photo.
Valves are made by hot upsetting the head shape on the end of a steel bar. Axial forging might be a good description. Several additional operations result in the finished valve. The grain of the metal spreads out from the center to the edge of the disk. The machined valve seat exposes the end grain to the hot gasses. End grain is the most susceptible to corrosion and erosion.
The applied stresses on a valve head rim are complex and not intuitive for me to understand. The erosion pits around the entire seat indicate that the valve may not have been seating in the head for a long time. The hot gasses were carving out seat material with every stroke. Some spot decides to be worse than the others. Nature finds the weak link.
The fracture can open but not fully fail for some time. During this period, the fracture face is exposed to the hot environment and becomes dark. The dark area at the seat on the right side is the most likely origin of the fracture. Microscopic fracture analysis is not possible since the fine detail is smoothed over by the hot gasses. I can make out two dark arcs as the fracture spread through the uniformly thick portion of the valve head. The thickness began to increase as the crack moved toward the center of the valve, the crack then turned back toward the rim. The angle of the fracture plane also changed to 45 degrees relative to the original plane of fracture. This often called the shear lip. This is the rapid part of the fracture.
None of this may be true, but it has been well imagined. (Arthur Clarke)
Roy

[FuddyMucker]

Wow Moncha your brother-in-law really knows his stuff, impressive!
I don't remember it running hot but can see where he means (now you have pointed it out).
So a full rebuild is in order then, sounds expensive but fun, I do like tinkering although it would be nice to get to drive it more than 50 yards before I get yet another problem.

So what you are saying I need to do is

1. remove the other head
2. remove all 4 cams
3. remove all 24 valves
4. remove all guides
5. remove all seats
6. get both heads skimmed
7. buy new valves, guides, seats and headbolts
8. rebuild both heads
9. buy complete gasket kit
10. rebuild engine


Surly if I am going to go that far it would make sense to drop the bottom off the engine and replace the piston rings and main engine bearings.
******Then I would have a new engine******

[FuddyMucker]

Roy, I actually had to read that 5 times to fully understand what your were saying (dosen’t help I’m working nights at the moment), very interesting stuff.
I guess you also think, if one valve hadn’t been seating well for a while then it is probably not the only one getting to your well described condition..
I am also guessing that its a 50/50 chance of the chip being blown out as it is falling back into the engine and destroying the cylinder lining?

[Ldub]

Has anyone else done a head gasket before and not replaced the head bolts?
Has anyone else in the UK managed to get hold of head bolts?

Here are a couple of examples of why i recommended head bolt replacement...:_wrench:

http://www.vehicross.info/forums/showpost.php?p=77513&postcount=19

http://www.vehicross.info/forums/showpost.php?p=77389&postcount=10

The links I posted for head bolts ship world wide, though a vendor in the UK would probably be less expensive.

[Moncha]

So what you are saying I need to do is

1. remove the other head YES
2. remove all 4 cams YES
3. remove all 24 valves YES
4. remove all guides YES
5. remove all seats YES
6. get both heads skimmed YES
7. buy new valves, guides, seats and headbolts
8. rebuild both heads YES
9. buy complete gasket kit YES
10. rebuild engine Maybe

Surly if I am going to go that far it would make sense to drop the bottom off the engine and replace the piston rings and main engine bearings.
******Then I would have a new engine******

The heads, go without question, do them all and do them right or you are headed for another failure. The weak point in the head, and block is where the center cylinder meets up with the two outer cylinders, as there is a lack of water jacket between them. The engineers are relying on convection to keep it reasonably cool but when there is an overheat, those valves will be the victims for sure. The valves, especially the exhaust, rely on contact with the seat to cool by convection, in this case, that valve, whether it was a weak spring, guide galling, or gross mal-adjustment, stuck open, causing hot gases to constantly blow by, thus overheating the valve, thus burning it (Like Roy said) then causing the tell-tale 45deg notch break.

Depending on what your low end looks like. From the pics, it is quite impressive that you still have crosshatching on the piston cylinders after that many miles/kms. If there was an overheating situation, then there would be quite a bit of crap floating in the oil (however microscopically) so the bearings, rods and mains, could have some wear or galling. You won't know unless you look. If it looks good and clearances are in range than you could get by without. But........

[lasturbo]

Did the burnt valve chunk that is missing disintigrated cuz I did not see any damage to the piston and wall in the pics?

[FuddyMucker]

No it didn't disintegrate, it luckily got blown out the exhaust manifold into the cat.
If it had fallen back in to the piston it could have destroyed the engine beyond economical repair :(

[FuddyMucker]

OK, just spoken to a Isuzu mechanic at the Isuzu main dealer for Exeter and he has checked on his system and can confirm that they are not stretch bolts on the 3.2.
In his dealer manual (which he won't let me have a copy of :( ) it says to inspect the bolts for signs of wear and replace if necessary. He also said that they have only ever done a hand full of 3.2 head gaskets but can't remember ever needing to replace the head bolts on any of them.

I'm guessing they only needed to move over to stretch bolts when they increased the engine size from 3.2 to 3.5 :confused:

If I do need any he can order some in and post them out to me at £7.59 + vat each!

[FuddyMucker]

Picked up my new valve earlier (from a Frontera 3.2 V6) and :happyfaceYes:grino: it is the same.

http://i47.photobucket.com/albums/f182/FuddyMucker/VX/IMG_3085.jpg

While I was in there I also asked them if they have a listing for headbolts?
They said they had nothing listed because they are not stretch bolts, I asked him how he could be so sure? and he showed me this..

http://i47.photobucket.com/albums/f182/FuddyMucker/VX/IMAG0168.jpg

:) Now I will be 100% happy to reuse the headbolts :)

[VX KAT]

Yer killin' me here...cuz I don't understand this stuff & I'm curious....what's a stretch bolt and why shouldn't you re-use the bolts? Already stressed? Is all that black carbon/soot "normal" or should those 1st pics posted be much cleaner?
OK, I could look this up on the intent but you all are more fun...:bgwb:

Newthings....My background is kinda similar to yours in failure analysis, except my expertise was in healthcare...investigating when medical things fail or go wrong....surgery, medications, instruments, human error....etc... so I'm like the National Enquirer.."Inquiring minds want to know". :p

And Fuddy can you trust that book? My mechanic has a reference book that says our 3.5 engine IS an interference engine...when the pros here says it is NOT.

[Moncha]

Ok, Kat, for the stretch bolt part, I'm gonna make you read something that was already written. http://www.gomog.com/allmorgan/stretchbolts.html This pretty much says it all.

The carbon on those/that head and piston actually looks pretty good. Thanks to fuel injections and computers. You will almost always have something left over after burning a fossil fuel, hence air pollution :)

We never said that it/they was a "stretch bolt"... On my side of the conversation, it's just common practice. Weak link of the chain kind of deal. Our machine shop figures that if the bolts have been through untold number of vibrations, wear, tear, heat cycles, over heat cycles, cool cycles, etc. Best practice is to replace.. The end decision will be yours.

Interference engines? Last thing I knew, the 3.5 was an Interference Engine.

http://www.gates.com/common/images/Gates/ezlit/interfer1.jpg
Non-Interference

http://www.gates.com/common/images/Gates/ezlit/interfer2.jpg
Valve/Piston Interference

For the most part, even if it wasn't an Interference, I wouldn't take any chances. I had a '88 Acura Integra 1.8 Non-Interference with 300k on it. Lost the timing belt, the was just enough carbon built up on the piston and valve that it cracked the head from the collision anyway. They may be non-interference from the factory but will it stay that way?

[Ldub]

http://vehicross.info/forums/showpost.php?p=181837&postcount=21

[VX KAT]

Excellent! Thanks Scott! I totally understood the stretch bolt info.

Interference v. Non-interference? I'm still not sure...:_confused
Here's where I got some info:

http://www.vehicross.info/forums/showthread.php?t=16545&highlight=interference+engine (especially posts 20-24)
http://www.vehicross.info/forums/showthread.php?t=11466&highlight=interference+engine
http://www.vehicross.info/forums/showpost.php?p=96930&postcount=2
http://www.vehicross.info/forums/showpost.php?p=154574&postcount=50

[VX KAT]

http://vehicross.info/forums/showpost.php?p=181837&postcount=21
Once again, great minds think alike...;) Or at least VX minds....:rollo:

[Moncha]

Thank you dub, you and Sue have mastered the Search Engine

[FuddyMucker]

I have now run out of daylight :(
But have had a good day.
I have removed another exhaust valve for inspection

http://i47.photobucket.com/albums/f182/FuddyMucker/VX/IMAG0171.jpg

And going on the seat condition of the second valve I have ordered up a complete set, looks like it will be off the road a bit longer..........

[Ldub]

Thank you dub, you and Sue have mastered the Search Engine

Ain't none of it possible without you Boss...:yes:...:thumbup:

[Moncha]

...And going on the seat condition of the second valve I have ordered up a complete set, looks like it will be off the road a bit longer..........


Wise choice

[SlowPro48]

Sooo.... is the pitting on the face an indication that this valve was in need of adjustment - or is there a leaking valve guide seal and what we're seeing are problems caused by oil coking? The one in the pic was wire brushed right? How about a pic of one before it's cleaned up...

[Moncha]

Indeed, the pitting is an indication of mal-adjustment. Once its this far though it is too late. Most importantly with exhaust valves is the need for them to close completely and correctly. The valves, especially the exhaust, rely on contact with the valve seat to cool by convection, in this case, that valve, whether it was a weak spring, guide galling, or gross mal-adjustment, the valve stuck open, causing hot gases to constantly blow by, thus overheating the valve, thus burning it, first causing the pitting then worse case scenario the valve head breaks.

The black on the dome of the cylinder in question in my guess is actually coolant coming from the leaking head gaskets. Not enough to show in the oil but enough to cause carbonization. I don't think there is enough oil to really cause a "coking" as the cylinder walls look to be in too good enough shape.

[Ldub]

I can't find it now, but wasn't there a reference to LPG conversion having a tendancy of burning exhaust valves?...:confused:.:_thinking

[PK]

I can't find it now, but wasn't there a reference to LPG conversion having a tendancy of burning exhaust valves?...:confused:.:_thinking

That there be my post in another thread.

http://vehicross.info/forums/showpost.php?p=187493&postcount=7

When LPG conversions first came out, they recommended that you changed the exhaust valves to those that had been made of?? or treated with?? Stellite.

IIRC it is a change in materials that makes the valve harder and allows it to withstand hotter temps.
But gee - that memory is about 20 years old - might have all changed since then.
Might also only work down under where the exhaust gasses fall out of the cylinders.
You guys up on top have to push the gas out.

Although, looks appropriate in this instance.
It would be nice to measure the adjustment of a few valves before dismantling, and then dismantle to check condition. If condition worsens with valves out of adjustment, that would just about pin it down.

While I am on my soap box - I agree with Scott - replace the head bolts if you can get them.
Cylinder head gasket crush is one of the hardest things to get right when assembling an engine, and new bolts just add that little bit of extra insurance.
I have done it with old bolts, but only on older cars (pre 1980) when the torque values are lower, and the cylinder pressures less.
On those engines, I had to re-torque the head after about 1000 miles.
Some of these newer engines even have a "waisted" neck on the bolt (reduced diameter) to control the plastic deformation.
That type of bolt cannot hold the same tension when used again.

PK

[Ldub]

No wunner I cunna find it...:_thinking...:laughing:

Thanks PK...:thumbup:

[Ldub]

Here's a discussion on the subject that i found when i goog'd "LPG conversion valve burning"

http://forum.australia4wd.com/index.php?showtopic=5330

I found this post informative...http://forum.australia4wd.com/index.php?showtopic=5330&view=findpost&p=42009

There is more...LOTS more

[psychos2]

We reuse head bolts all the time . Some of the motors are 1300 hp. Some stock big blocks. If it says they are reusable then reuse them. Put it this way do they replace the main bolts when rebuilding? No and they are more stressed than the head bolts. You can tell when there is a problem with the bolt as it will not torque properly as the bolt is actually stretching and if you keep trying to torque it ,it will break. Just make sure to clean the threads in the block and the bolt threads so you get the proper torque. shawn

[SlowPro48]

Thanks for the info Scott. I guess coking isn't the proper term since coke comes from coal but that's what I've heard it called when oil gets turned to pure carbon on a hot engine part. Maybe we should call it "cooking" instead! Anyway the reason I asked is because I had an old four stroke dirt bike once that had that type of valve face pitting and I always suspected leaking valve seals was the cause. It was a "second string" bike that I kept after getting a new one because I wanted something to plod around on that I wouldn't feel guilty not washing after every ride. It smoked for a minute or two after cold starts but then cleared up and ran just fine so I didn't want to take time to install new valve seals. Then it lost compression. Not completely but enough that it was down on power and hard to start. The valves had always been adjusted - if anything a little on the loose side. As they say a ticking valve is a happy valve. It had rockers. I don't think they say that anymore now that shims are so prevalent. But anyway when I pulled the head, inverted it and poured some gas in it, it came out the exhaust port in a matter of seconds. Aha! Leaking exhaust valves. When I removed the valves I discovered that they were being held slightly open by baked-on carbon. It wasn't the nice, even, fluffy coating you'd get with running rich though - it was in one area and hard and crusty - took a knife and a Dremel with wire brush to get it off. My hypothesis at the time was that oil from the leaky valve guide seal was running down and pooling up in the same place every time I parked the bike and then cooking on the valve when I fired it up. Most of the leaked oil went out the pipe as a blue hydrocarbon haze but some stayed on the valve and cooked. The cooked carbon layer just got thicker until it finally interfered with the face/seat seal causing a slight leak - and a hot valve - because as you said the valve depends on conduction for cooling and there's not much conduction going on if the valve and seat aren't touching. So then I had overheated, leaking valves - and that's probably when the pitting started. My valve faces looked exactly like FuddyMucker's. Didn't replace 'em though - there was plenty of margin left so I just lapped 'em and slapped 'em back in there. Definitely replaced the seals though...

Figured it was probably a lash issue but now you know why I was wondering about valve guide seals and coked oil.

Those pictures sure make me want to check valve clearance! Guess I can add that to the list of things to do at 100K miles - which is looming - less than 500 miles away now..

OK that's my long-winded, thread jacking post for tonight.

[FuddyMucker]

Hello again Guys, sorry it has been a while since my last update but life has been a bit sh*t recently and I have had other things on my mind..

I managed to rebuild the head and fitted new valves and seats where needed. I also removed the other head and inspected it and it looked like it had already been done, it had an aftermarket head gasket fitted and the valves looked like they had only done a few thousand miles.
I rebuilt the engine with a complete head gasket kit and also fitted a new cambelt and tentioner for peace of mind.
I have done 1500 miles in it since the rebuild and am happy enjoying the extra few horses it has found. :yeso:
I even had the LPG system re-tuned to make the most of that new power, I love running this VX on LPG because it drives the same as on petrol but at half the price, makes a real diffrence here in the UK with petrol at £1.25ppl and I'm only paying £0.58ppl for LPG (guess it is still expensive compared to the US though).