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04DII
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20 Posts
Discussion Starter · #1 ·
2004 Disco II; 165k. Losing coolant slowly (no leaks), engine misfires for brief time after starting. 0306 code (Cyl 6 misfire) is consistent, no other codes. Replaced head gaskets last winter. What is the procedure for determining if the liner in #6 cylinder has slipped?
 

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'03 Disco SE
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573 Posts
Typically you'd do a block pressure test, however without stripping the engine down to the short block it's difficult to tell if you have a slipped liner, cracked block, or blown head gasket as they'd all show similar symptoms. Pull the #6 plug and inspect it for steam cleaning. If there is enough coolant in the combustion chamber to trigger a misfire it would almost certainly show up as steam from the exhaust. Is there steam present?

A slipped liner would be pretty noticeable. You'd hear a distinct knocking sound after the engine was warmed up. Get a stethoscope on the block around #6 and see if you can't hear the knock. Also, a liner wouldn't slip out of the blue, it's typically a product of a serious overheat. Did you overheat the engine before your last head gasket job?

I'm leaning towards a failed valley pan gasket or head gasket. It's not uncommon for them to fail shortly after a replacement, particularly if they heads weren't machined or the (hopefully new) bolts weren't torqued properly.
 

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16,594 Posts
Does the engine tick, if so when, hot or cold? Did you have the heads pressure tested when doing the head gaskets and did you use new head bolts?
Was the #6 cylinder the issue before you did the gaskets?
 

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04DII
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20 Posts
Discussion Starter · #4 ·
Thanks for the quick responses. Great questions and suggestions.
Yes, the #6 cylinder misfire and missing coolant was the issue that prompted the head gasket work last Dec. I did have the heads pressure tested, rebuilt and machined while they were off. New head gaskets and bolts were used, and careful adherence to the torquing procedure was followed. If I have to pull the heads again I'll be curious as to the current torque status, which I'll check before loosening the bolts. I've never seen this procedure of pulling to a starting torque then adding 1/2 rev to final. Since you really don't know the final torque it takes away the option of rechecking the torque a couple of weeks after the work, which has always been my routine.
There is no knocking or tapping sound from the engine that I can hear, and it runs great, including when pulling my trailer, except during the first few minutes when the misfire is occurring. I have noticed no steam during the misfire, but it doesn't last long and I haven't been specifically checking the exhaust. I will do that.
There is no history of overheating with the engine except for a blown hose a couple of years back, which I caught well before damage could have occurred.
When replacing the head gaskets last year I couldn't see evidence of a failure. However the symptom stopped after the work and didn't start up again for a couple of months. It has been very infrequent until recently, when it started happening pretty much every time I start up.
I thought it unlikely that a botched job on my part would result in the problem coming back to the same cylinder. Possible, but unlikely. More likely that I botched the valley pan or some other gasket installation.
I'll pull/inspect the plug tomorrow and put a stethoscope on the block to double check for a knock. My gut tells me the truck wouldn't have lasted this long with a slipped/slipping sleeve.
Would a borescope inspection of that cylinder with the cooling system pressurized (using a coolant system pressure test kit) reveal the source of the problem?
Couple of questions:
Why does the misfire stop? Surely if a leak is occurring it doesn't stop after the engine is started...
It seems the truck has to sit overnight for the symptom to occur, and the amount of coolant being lost is minimal - around one cup a week; sometimes a little more, sometimes less. The misfire doesn't ALWAYS occur. Last week I drove from Baltimore to Atlanta without any misfire. But it sat for a few days during the visit and when I headed home it misfired for several minutes before smoothing out - then made the rest of the trip, and a couple of days driving afterward before the symptom reoccurred.
Thanks for the help and your thoughts.
 

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04DII
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20 Posts
Discussion Starter · #5 ·
I'm going ahead with obtaining parts for a top end rebuild.
Any particular head gasket kit to look for?
Do you guys recommend switching to ARP studs from bolts?
What else should be replaced on a top end job?
Thx
 

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I have headsets for your truck for $205 shipped with new bolts.

I have yet to replace the SAI adapters and have had no problems.

No sealant on the head gaskets please!
 

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'03 Disco SE
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573 Posts
Do some additional checks before tearing into it.

- Pull the #6 plug and see if it is steam cleaned.
- Swap the #6 injector with another cylinder's to see if the codes and misfires follow.
- Swap the #6 wire with the opposite bank to see if the codes and misfires follow.
- Reverse the two coil packs to see if the codes and misfires follow.
- Do a compression test on the engine and see if #6 is drastically different from the rest.

I really don't think it's a slipped liner - it's an issue that typically exhibits some pretty serious symptoms and is typically caused by a pretty serious overheat - you have neither. You seem quite mechanical so I'll take you're word on this.

Also - our cars have a nasty habit for hiding coolant leaks and having them seem like HG's. Very often with no leak evidence on the ground. Double and triple check every coolant connection to ensure there are no leaks. Get a hold of a UV leak test if you want to be absolutely certain. No steam out of the exhaust is a pretty decent sign that you don't have an internal leak.

I have had minor leaks from the TB heater itself.
Leaks at connection of TB heater hose and intake manifold.
Leaks at connection of TB heater hose and expansion cap.
Pinhole leaks at plastic "T" fitting in lower coolant hose. (Where it connects to water pump)
Pinhole leaks from top of radiator.
Leaks from heater attachment o-ring.

Most of these leaks didn't manifest themselves as drips or puddles. I only managed to trace they by waiting for the engine to dry and looking for coolant residue.

At this point I think you have a hidden coolant leak and perhaps a sticky injector. Injectors cycle pretty rapidly - if they have carbon buildup or if their components are damaged they'll likely stick when cold - at startup. Swap it with the adjacent cylinder to see if anything changes. Oftentimes you'll be able to see gun or carbon buildup at the outlet.

Good luck man - I really don't want you to have to tear into that motor again.
 

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04DII
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20 Posts
Discussion Starter · #10 ·
Bosnian Discovery - thanks for the considered response. All great thoughts. I also can't really sell myself on a slipped liner, and the fact that it has not gotten any worse over the past year says something, although I'm not sure what. I am still kicking myself for not swapping the injector to a new cylinder when I had it apart the last time - I intended to and just got in a hurry to get it back together. I put in new plug wires in the last go-around but it wouldn't be a bad idea to move that as well. Changing something and seeing if the problem follows the change is a basic troubleshooting technique I should have already covered. I'll get to work and post the results.
thanks again
 

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04DII
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20 Posts
Discussion Starter · #11 ·
Update

Turned out to be a bad injector and a coolant leak. Haven't found the leak yet (pressure test kit on order), but the new injector eliminated the misfire.
Thanks for the suggestion to keep digging before tearing into the engine again.
 
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