Constant miss running really rough

[paulv1818]

Hi Murphysegg, yes plugs were good but I haven't checked for headgasket failure. This could well be a legitimate issue but I wasn't seeing any telltale signs, coolant in exhaust, bubbling in rad, white oil, getting hot etc. i was getting more the smell of unburnt fuel in exhaust.
I've started looking for another vehicle - this ones in the marketplace, but i'm going to still try to get it going in the meantime

[erad]

Looking at the photos, obviously one cylinder is not firing correctly. Is it the HT lead at fault? Check it in a very dark area and see if you can find arcing to earth.

[Murphysegg]

Hi 'paulv1818', i've had no indication of a head gasket failing in respect that i don't see any bubbling in the radiator, have never seen the temp gauge climb above 3/4, no milky oil & it doesn't appear to consume water other than a top up of the Expansion tank every few weeks.

I'm starting to lean towards replacing the Head gaskets myself but want to confirm this to be the issue before i commit the time & effort. The Paj isn't a daily driver but is used seasonally on solo Beach runs to get to fishing spots, so i need reliability as RAA recovery is not an option.

Can anybody recommend a sure way to tell of Gasket failure before strip down ?

[erad]

Hi 'paulv1818', i've had no indication of a head gasket failing in respect that i don't see any bubbling in the radiator, have never seen the temp gauge climb above 3/4, no milky oil & it doesn't appear to consume water other than a top up of the Expansion tank every few weeks.

I'm starting to lean towards replacing the Head gaskets myself but want to confirm this to be the issue before i commit the time & effort. The Paj isn't a daily driver but is used seasonally on solo Beach runs to get to fishing spots, so i need reliability as RAA recovery is not an option.

Can anybody recommend a sure way to tell of Gasket failure before strip down ?

First thing - check cylinder compressions. If 4 of them are good and 2 adjacent ones are lower, - head gasket. If one cylinder is low, it could be a valve or head gasket. If the leak is bad it ill show up this way.

I had a Range Rover V8 which developed a small leak in one head gasket. Compression checks showed no significant difference between cylinders, but the beast used to occasionally make water - the overflow bottle would be full one morning. When I checked the radiator, it would be very low. It took a while, but I eventually narrowed the problem down to when the best had been climbing a long hill. One day, I was climbing a long hill on a hot day and I felt a sudden drop in power. I noted the temp gauge position (it used to climb above the normal running position, but not into the red). I guessed it was a head gasket. Which one? I guessed it would be the most inaccessible so I did that one first. When I pulled the head off, I could see very minor tracking between No 6 and No 8 cylinders. I checked the head with a straight edge, and there was a slight bow in the machined face. I had it lightly machined and refitted it - all good. In retrospect, because the leak was so minor, I could have probably tightened the head bolts a little tighter, particularly in the middle, but with all the bother to remove and replace, it was not worth the effort - do it right the first time.

As said above, compression checks at cold temperatures showed no real difference - it was only when it really warmed up that it leaked.

[Murphysegg]

Thanks Erad. I'll look into conducting a Compression test on Cylinders 1,3 & 5.

[erad]

There is a simple way of testing for head gasket leaks. I have not used this, but it involves a gas analyser in the coolant, checking for signs of exhaust gases. Obviously not a backyard instrument, but if you can find someone with one, it may save you a lot of time and effort getting to the spark plugs to check the compression (it is not an easy job and to check things when hot is almost impossible). With my Rangie, the compression tests showed nothing and I ultimately discovered that when the temp gauge got to a certain level it suddenly dropped power and the temp gauge went even higher then.

For what it is worth, I never saw the temp gauge on my NL go over halfway, even towing my caravan up a long steep hill. I had an Engine Watchdog fitted to one of the intake manifold studs to monitor engine temperatures, and it used to show a minor increase in coolant temperature, but typically the coolant used to get hotter when travelling slowly in heavy traffic.

[Murphysegg]

Yeah. I seen a few Utube vids on the Gas analyser kits. They seem to be a reliable test. Repco have them priced @ $150 which seems a bit excessive for something i'll probably only use once. I may phone round some w/shops to see if they offer a diagnostic service.

[Murphysegg]

Ive decided to replace the Drivers side cylinder head as #3 cylinder is clearly suffering from coolant contamination, & i have managed to locate a pair of Resurfaced heads complete with an unused VRS gasket set for a good price.
My thoughts are with replacement heads prepped in readiness, this will allow me to complete the task with minimal downtime. Head off, head on.

The timing kit & water pump are only 2 yrs old with approx 22k's use so i don't intend on replacing these.
My only additional purchase would be to get a set of replacement Head bolts, so my question is do i just replace the Drivers side head or replace both ?

I don't believe the Pax side is showing any signs of issues, however if it's just a couple more Hrs work to replace both as a pair ? What does concern me is removing the exhaust manifolds as i've never had these off since owning the car & am all to aware how a stubborn stud can consume the best part of a day.
Thoughts anyone ?

[brw0513]

I've just had the heads off my 6G74 NL. It was a fiddly job, but I enjoyed the process and would recommend doing it, especially if you have a pair of heads and gasket kit ready to go.

The right side head (driver's side) appeared the worst due to oil weeping past the front cam seal, oil filler hose and rocker cover gasket. It required a 0.006" skim to get flat. The passenger side head looked better, but required a 0.008" skim. That is actually a hair beyond the MM limit of 0.2mm. Appearances can be deceiving.

Are you going to lap valves and replace valve stem seals?

If you are interested I will gladly post lessons learned here. There were a few but probably none not already published.

But if I was to do it again, I'd buy a cheap dining room table off Gumtree and modify it so I could use it as a platform to lie on while working over the back of the engine. There is lots to do back there.

Don't underestimate the time the job will take though. The exhaust manifold studs are relatively easy to get off. The nuts joining the upper exhaust pipes to the manifold are very awkward to get do and will have you cursing MM. I removed the starter motor to get access from below.

You might find your cast exhaust manifolds are cracked. Mine were and I'm led to believe this is a MM design feature

The coolant pipes over the back of the engine (the cast aluminium crossover pipe and the the pipe out the back of the water pump housing) are also a pain to get to. This is where the dining room table would be very handy. The genuine MM gaskets for the crossover pipe have VERY handy tags to hold them in place during assembly.

[erad]

When my friend stripped the engine on my NL, I had removed the bullbar before the work started. This made access to the engine much easier ,except for the bonnet release lever which stuck into our bellies every time we needed to reach over the engine. Getting access to the rear of the engine is not easy.

[brw0513]

Yep. I had bonnet release bruises fairly constantly.

[Murphysegg]

I'm hearing ya Guys. I have a couple of old pillows for such occasions.
The seller of the Heads sent me a pic of the VRS kit which is unopened however it appears to be for a DOHC not a SOHC. I've confirmed the heads are definitely SOHC.
Is the difference between a DOHC & SOHC mainly relate to the Rocker cover gaskets ? ie. the Head Gaskets, Valve stem seals, Cam seals are essentially the same ?

[brw0513]

I don't know too much about the DOHC version, but the Supercheap Auto website is a good place to do research.

You could create a "virtual" garage of different Pajero model/engine variants and see what gasket sets are available for each version. You might get lucky and see the same listing for different engines.

Bursons would also be helpful. I often purchase from my local-ish Bursons store because they employ very helpful staff.