[Entabeni]

From Entabeni 2014-01-04
Pajero 2006 3.2 DiD LWB GLS Auto, Gen3, 4m41 motor, 204,000 km.

ENGINE FAILURE:

Vehicle history:
Bought in Somerset West in August 2010 with 150,000 km on clock and going very well indeed. We have made two trips to Namibia including Etosha and the coast road down via Swakopmund, Sesriem, Sossusvlei, etc. Also northern and eastern Transvaal, the KNP and Natal and Lesotho via Sani pass, including a terrible minor road to Katse Dam on which the three under-car cover plates were damaged. Overall fuel consumption is close to 10 l/100km. On long uninterrupted trips with A/C on and cruise control at 120 km/h we get 9.6 l/100km. When, very occasionaly, we include town driving it rises to around 12 l/100km.

I gave it its 200,000 km service while in JHB in October, returning to the Cape via Matatiele, Qacha's Nek and southern Lesotho. In December I did a 20 km trip locally on a good tar road. On starting the motor for the return trip it seemed to hesitate briefly. I drove the 20km home at 100 km/h and thought that I saw smoke behind the vehicle, but there were scattered clouds and I thought that it might be alternating sun and shade on the road.

Evidence of engine failure:
(1) On parking in the carport at home there were billowing clouds of grey/white smoke from the exhaust! And a slight clonking sound from the motor when I lifted the bonnet! When revving slightly it was clearly misfiring on one cylinder.
(2) On unplugging the small pipe which discharges vapour from the crankcase and camshaft cover into the large corrugated rubber pipe which feeds clean air to the turbo unit, then starting the motor, a jet of smoke emerged from the small pipe but much less from the exhaust. This sugested that the smoke came from the crankcase. Questions : Hole in piston? Broken rings? Valve clearance? Valve and/or seat burnt?

Investigation:
(3) Removed the viscous fan and its surround for access to the crankshaft pulley bolt.
(4) Removed EGR tube and camshaft cover to enable valve clearance check. This is quick and easy.
(5) Rotate crankshaft in clockwise direction, (seen from the front of the vehicle), to the TDC preceding the power stroke for each cylinder.
(6) Place finger on the adjuster bolt on the outer end of each of the 4 rockers of that cylinder and feel if they can be rocked. All the valve clearances were OK, so the failure was not caused by lack of valve clearance.
(7) Removed the 4 glowplugs. They came out easily and there was still plenty of Copperslip on their 10x1.25mm threads, (from the 170,000km service). Their resistances all measured close to 1 ohm, so all OK.
(8) How to test for hole in piston or broken rings? I decided to make an adaptor to screw into the glowplug holes and to which my compressor and tyre pump with pressure guage could be attached.
(9) I found a 65mm steel bolt with 25mm of 10x1.25 thread and 14mm hex head and checked that it screwed easily into the glowplug sockets, Then drilled a 5mm hole right through it (on my lathe) and a shorter 6.1mm hole into the head end to accept the 6mm brass portion of a car tyre valve from which I had cut the rubber away. After degreasing and roughing up the surfaces I glued the valve into the bolt head with epoxy.

Pressure test:
(10) In the first test I positoned each piston just 2 or 3 degrees past TDC, then screwed the adaptor into the glowplug socket, attached the pump nozzle and, tightly holding the power-bar with 24mm socket on the crankshaft bolt to prevent rotation, applied 600kPa of pressure to the cylinder. On releasing the pump's lever the pressure indicated on the guage dropped back to zero so rapidly that it was difficult to detect any difference between cylinders. The volume being pressurised was too small.
(11) It would be better to do the test near BDC (bottom dead centre) so that the whole swept volume is pressurised --- the problem is that the exhaust valve begins to open before BDC. So I slowly rotated the crankshaft through the power stroke while keeping a finger on the cylinder's rear exhaust rocker (which opens slightly earlier) to find where the gap started to close. In this position pressurising the cylinder applies torque to the crankshaft, so to prevent further rotation I kept the power bar and socket on the crankshaft bolt and wedged the handle with timber. Applying 600 kPa to the cylinder and then releasing the pump lever, the pressure dropped quite slowly towards zero. This result applied to cylinders 1, 3 and 4 (that being the firing order). (By the way, that torque is considerable!)
(12) When it came to cylinder 2 in the near-BDC test, the pressure disappeared almost instantly and no crankshaft torque could be felt. One could also hear the sound of the compressed air going into the crankcase coming up through the timing chain housing! So the problem cylinder has been identified.

Next step?
(13) Drain oil, remove sump, remove No2 big-end cap and remove piston 2 from its cylinder. Examine all for damage, etc! A carport in Robertson is not the best place for this, but what the heck, this is life.

Comments and suggestions welcome.

[CATS]

Sjoe. You seem to be well setup and prepared to take on anything with a 'make a plan' attitude! Respect!

I think you have found your problem which probably is a small hole in piston 2. If you decide to repair I would also do all the other pistons as I believe the damage probably came from excessive piston temperatures due to incorrect spray pattern by injector and if one was worn enough to cause this then the others are probably not far off. So you would probably look at replacing all 4 cylinders(edit I meant pistons, sorry) as well as injectors.
Have you ever had the injectors checked or replaced? I am a firm believer in at least checking injectors every 100000km and preferably replacing them in any case.

Thanks for your detailed feedback. Please keep it up until resolved. Be aware that 4m41 engines seem to be notoriously difficult(from some failures reported on the net) to rebuild so be sure to take great care.

CATS
My 3.2 is also preparing for surgery at 298000km but mine seem to be diesel pump related.

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[CATS]

By the way you dont perhaps have an EGT monitor fitted to your vehicle? If you do did you see any funny readings before the failure? I have one fitted and am trying to determine if it will help in any way to detect stuffed injectors in advance.

CATS

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[Entabeni]

CATS -- Thank you very much for your reply to my post. I did not realise how important the injectors are. I will certainly have them serviced or simply renew them as you suggest. If piston 2 is damaged then I will replace all pistons plus the big end bearing shells etc etc. The question is where to go for these spares here in the Cape.

If the cylinder wall is damaged then a full rebore will be neccesary too which means removing the engine. I have a 2-ton shop-crane with which I removed my Audi 500SE motor some years ago, so that should be capable of doing the job.

On the question of an EGR (or EGT?) monitor, I'm afraid my Paj doesn't have that --- sorry, and thanks again.

[CATS]

I think you might find the cylinders to be still in good nick and possibly would not require rebore. So maybe just new pistons, rings and bearings. I would start at the agents for parts and then work from there. Bear in mind though that I have 10 thumbs and am only an internet mechanic so these comments are just based on some readings of my own over the years on these engines as I have put just over 200000kms on my 4m41 and have been trying to keep up to date on them as much as possible.

CATS

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