Pedro the Pajeros’ 4M41 engine rebuild.

[Nick Gibson]

Following on this thread https://www.pajeroclub.co.za/forum/view ... =24&t=6576
I have decided to rebuild my engine, this is the story.

History:
At the time of the failure I suspected the cylinder head had gone, so I pulled the head for it to be replaced with a new one, and once the engine was open I saw some damage to the cylinder wall and what I thought were cracks.

Damage to sleeve

Head No. 2

We did a 5 bar pressure test on the head which initially passed, I then pulled and stripped the engine down completely and had the block itself pressure tested, which also passed, no leaks at all from the suspected ‘cracks’ in the sleeve. They pumped the block up to 6 bar. We then removed the valves in head to pressure test the head again and found a slight leak in the no2 cylinder injector tube, and a lot of white residue in the one inlet valve port of no.2 piston – the leak was found; that also answered the question why I did not get bubbles in my coolant when I did various load tests on the engine at silverrons as the head leak was outside the combustion chamber. So essentially every time the inlet valve opened on the downward inlet stroke, some coolant was passed into the cylinder with the boost air and being burnt out the exhaust as steam, and no exhaust could get into the coolant as the intake valve is closed during combustion.

Inlet valve no.2 -white residue inside

Block Repair:
We then bored no.2 out to 20thou of an inch (0.5mm) to see what the ‘cracks’ looked like deeper in, and they disappeared. Good news, block is fine. We then proceeded to bore the whole block one oversize (99mm from 98.5mm) and cross-hatch hone. What the machinists recon happened is that due to the slight head leak, some coolant was lying on the piston ring slightly rusting the liner along its horizontal line, this process over time slowly ‘etched’ a horizontal defect in the liner which was removed by the re-boring and honing process. They also were baffled at the line in the sleeve, having never seen something like it before, and were adamant the 4m41 blocks are ‘bulletproof’ and do not give issues.

Tools Required:
I bought a 450kg engine stand from adendorf (very important) to work on all sides of engine

Engine on stand

, 0-100mm 4 piece micrometer set (check tolerances of crank & cam-shaft, etc.), dial gauge with magnetic stand (Piston protrusion/heights), 500ml groz oil squirt can (to lube all parts up during assembly with DELO400), borrowed a calibrated 20-200Nm Gedore torque wrench for a bottle of whisky. 5kg bag of rags at 5lt of prepsol engine cleaner finished it off to clean up the engine thoroughly before assembly.

Parts Bought:
I bought a full engine bearing set, (small ends, big ends, mains and thrust washers), riken rings and new pistons from alert engine part. I also found a Victor Reinz 4m41 engine overhaul seal & gasket kit, which has every possible O-ring, gasket, copper washer, injector nozzle gasket, main & rear crank seal, intake/exhaust manifold gasket included in it – very convenient indeed. I will buy the correct notch cylinder head gasket once I have done the piston protrusion when the engine is together. I also used the Rienz-o-sil liquid gasket to keep it from leaking (hopefully).

I will post pics and info as I progress.

[Nick Gibson]

I am also definitely blanking my EGR off when I saw what the stems of my intake valves looked like from the gunk deposited on them. You can clean the intake manifold, but you cannot get to the deposits on the valve stems without stripping the head.

ERG gunk on intake valve stem

Ps:
Look how clean my exhaust valve is from using 2so.

[Nick Gibson]

Block on stand again being cleaned up.

For what its worth the bolt size and pitch for the rear bell-housing bolts holes in the block (to which the engine stand is bolted) is a M10x1.25mm fine pitch thread. I need 2 x 80mm and 2 x 100mm bolts to make it work. You can also just buy full shank threaded bolts and cut to desired length.

I then fitted the oil squirters, these spray oil into the hole and cavity in the bottom of the piston which keeps it cool.

Oil squirters & anti-drip bolt

I also made sure the spring valve inside the bolt works and no debris was in the small spray pipes with low pressure compressed air. I also blew out the oil gallery leading to the squirters and main bearings, don't want any debris from the machinists to block anything up.

I then cleaned the block up and lubed everything up with copious amounts of DELO400 and fitted the bearing shells to the upper block assembly.

Main bearing shells & oil squirters

Bearing fitted with oil underneath

[4ePikanini]

nice work. Time for an update.

[Roelf_le_Roux]

Amazing post. Thanks for taking the time and walking the extra mile to keep us informed.
Please keep it up.

[Nick Gibson]

Ok Update:

I cleaned the crank up of all the protective oil I applied prior to it's storage and made sure to blow all the oil channels out- I dont want debris!

Crank cleaned up & Oil channels blown out, look pretty good for 274k km!

Up close & personal -no damage

Interesting fact: The engine oil is fed to the small end bearings via an oil channel drilled down the middle of the conrod, which get fed from the big end bearing which in turn get fed via a diagonally drilled hole thorugh the crank-shaft from the main bearing journals.

Main bearing with a coating of DELO400 prior to fitting the crank

I fitted the two new orange 'O' rings sandwiched between the sub-block and block that carry oil between the two.

New "O" rings fitted to oil gallery between block & sub block cradle

Factory Manual states how wide the bead of sealant need to be for the various parts, this is the thinnest at 2mm.

2mm Wide Victor Reinz gasket maker applied

[Nick Gibson]

Cradle is dropped onto the block.

Cradle Dropped onto Block

Sorting bolts out to re-torque the cradle

All my bolts from the strip of the engine, pre-numbered.

Torque Steps are:
Main cradle Bolts (TTY bolts: Can be Re-used 3 times - per Factory Manual)
20Nm
90 Degrees
90 Degrees (This is very tight - the bolts were creaking so much when doing the last 90 degrees, it felt like they were going to snap!)
Secondary Bolts:
20Nm only

Bolts in their original places again.

Started to torque the bolts:

Bolts in and being torqued up.(Torque To Yield Bolts)

I removed the old rear crank seal and fitted a new one. Must say it is MUCH easier doing it off the car on and engine stand... The housing needs a wider bead of sealant, 3.5mm or so.

New rear seal & holder fitted (3.5mm Bead required).

[Nick Gibson]

I must say, the most tedious part of this re-build is the removal of the old silicone gasket maker off the stripped parts... Man, you need to sit there for ages with a small carpet knife blade and cut/scrape that stuff off!

Gasket maker removed from seal housing

One done underneath I flipped the engine around to get ready to start fitting the pistons & checking the ring gaps (0.3mm for 1st and 0.4mm for second ring).

Block turned around to start fitting pistons.

[nielsch]

Fantastic job Nick.

Like everyone else I'm following this post with great interest.

I see no reason why this rebuild wouldn't be 100% successful.
You seem very meticulous in your approach and in my mind that is exactly what is required to get these machines back to their former reliable selves.

It would however mean that future engine rebuilders would be lining up in front of your house!

Best of luck!
Niel

[Nick Gibson]

I then did a mock up fitting of the timing plate. This is bolted to the assembled block(s)-(Upper & Lower) with a bead of liquid gasket behind it, also 3mm thick.

Mock-up fitting of front timing plate

I then fitted the lower balance shaft - I got the new 'O' rings with the Victor Reinz service kit.

Lower balance shaft -new "o" rings fitted

Balance shaft fitted

Side note: The service manual give most, but not all bolt & nut torque values. I had to look up the specific items in the beginning of the service manual in a list. If they were not listed there you had to go on the torque table as below:

Manual Torque Tables

Upper balance shaft. This is driven off the oil pump gear, it was the one I found to be about 90 degrees out of alignment when stripping at 0 deg TDC.

Upper balance shaft port with sealant applied adjacent