[martinbo]

What can be the cause of a cracked exhaust manifold on a 2005 3.2DiD, LWB, 224500km on the clock, see picture?
Can this be the reason why the Pajero overheated, pulling the Kavango up Magoebas kloof?
I ordered a new manifold from Mitsubishi East Rand on the 25th of June, no stock, to be ordered from Japan. Phoned again this morning, still not arrived.
Can I drive the Pajero as is? What can happen?

[martinbo]

I think I discovered the reason for the cracked manifold. It looks like the crowd who fitted the turbo 21000km's ago did not tighten the bottom nuts on the manifold, as they are missing.
All the fundi's out there, can this be the reason for overheating under load?

[CATS]

Martin

I have researched a bit on cracked manifolds on the www.

Seem like some crack and some don't. Consensus is that it is better to replace than to repair. A cracked manifold can lead to incorrect measurements of the airflow meter? (IIRC) and will often result in overfueling and higher fuel usage. I suspect the overfueling on a diesel can possibly also then lead to higher heat in the combustion process and possibly lead to your overheating problem. Not sure though as this is all from my limited understanding. Do you have any EGT monitor device fitted? If so did you notice any difference in the readings lately?

CATS

[4ePikanini]

it could be caused by the missing bolts making the manifold vibrate and twist too much causing the fatigue crack.

The crack can cause over heating as the exhaust manifold releases exhaust pressure that is used to spool the turbo. Less pressure = less turbo spool = less boost = overfuelling = high EGT = overheat.

I wouldn't drive it like that unless at utmost need and then only baby footing it.

I would also recommend an exhaust gas test on the radiator to check if the headgasket is gone as well as a pressure test on the cooling system (A good radiator shop should be able to do both)

While you are working on the car get an exhaust shop to delete the catalytic converter with a straight pipe and if funds allow the big center silencer box with a freeflow box. This helps the turbo spool up better, reduces EGT and back pressure and frees up a fee ponies. It helps a marginal amount with economy as well.

[martinbo]

Thanks Cats and 4ePikanini for your replies.
No, I do not have a EGT meter, so I cannot tell what the temperatures were. The catalytic converter was removed on 100000km's
When I tow I watch the temp meter constantly and by overheating, I meant, it went to 3/4, never in the red. I stopped as this is not normal and in a short time span it cooled down to normal. I then took it slow, switched off the aircon and the temp stayed constant.
Before I did Magoebas kloof, I was getting a higher than normal engine temperature when towing uphill.
I forgot to mention, I think it was cracked already last year (15000km's ago) going down to Natures Valley, Garden route, Touring the Karoo and now in June the Krugerpark. The Pajero did warn me by making strange noises going uphill under load. I ignored it, thought it was the turbo's wastegate.
I removed the radiator and Silverton cleaned it by rodding it and removing all seeds and mud stuck in the fins. Apparently the top part of the radiator, inside, was blocked (Gelling they said). I refitted the sponges around the radiator, hoping I solved the problem, until Magoebas.
When my garden boy, painter, tiler, mechanic etc. cleaned the Pajero after Magoebas, he called me and showed me the soot on the manifold, I stripped the cover and found the problem.

[4ePajero]

A few points to ponder:

• Engine (coolant) temperature is seldom an indication of high EGTs.
• I would replace the manifold.
• Make sure it is the cause of a problem, rather than a victim (eg high EGTs)
• usually your valves and/or pistons will fail due to high EGTs before the manifold does, but not necessarily.
• Have an EGT gauge fitted ASAP. It is more important on a TD engine than a coolant temperature gauge.

[Gerrit Loubser]

The crack can cause over heating as the exhaust manifold releases exhaust pressure that is used to spool the turbo. Less pressure = less turbo spool = less boost = overfuelling = high EGT = overheat.

Marius, I doubt whether the exhaust manifold leak could lead to overfueling. Here is why I say this:

The injection pump ECU knows the engine speed, so the intake air volume flow can be determined from the engine displacement. The boost air pressure and temperature are measured directly, which means that the air mass flow and hence the appropriate fuel dosage can be determined (obviously taking the throttle pedal postion into account as well). Now if there is a manifold leak, which prevents the turbo from developing the boost pressure it normally does, then the boost pressure sensor will pick this up and the ECU will adjust the fueling appropriately.

[4ePikanini]

The crack can cause over heating as the exhaust manifold releases exhaust pressure that is used to spool the turbo. Less pressure = less turbo spool = less boost = overfuelling = high EGT = overheat.

Marius, I doubt whether the exhaust manifold leak could lead to overfueling. Here is why I say this:

The injection pump ECU knows the engine speed, so the intake air volume flow can be determined from the engine displacement. The boost air pressure and temperature are measured directly, which means that the air mass flow and hence the appropriate fuel dosage can be determined (obviously taking the throttle pedal postion into account as well). Now if there is a manifold leak, which prevents the turbo from developing the boost pressure it normally does, then the boost pressure sensor will pick this up and the ECU will adjust the fueling appropriately.

yes. 100%. Wasn't thinking there . I stand corrected.

[martinbo]

It is done!!
I have done the job myself and I am proud of it. Service levels in the motor industrie is not what it used to be. The people who fitted the turbo must have stripped the 3 studs on piston number 4 and that caused piston number 1's nut to vibrate loose. Normal use of the Pajero won't cause this.
I have replaced the manifold with a second hand one sourced from Gert in Pretoria, as the one from Japan is still not here.
After removing the manifold it was clear that the problem was caused by the missing nut at the bottom of the manifold on piston 1 and the 3 stripped studs on piston number 4. These two gaskets weren't sealing and a lot of pressure was lost here. The engine was covered in black soot at these 2 gaskets. The turbo was hanging on the studs from the number 2 and 3 pistons only and I recon that this is what caused the cracks in the
manifold, due to the vibration.
I discovered the stripped studs on reassembly when trying to torque the nuts. Stripped the manifold again, replaced the studs and this time I was able to torque all 12 nuts. I also fitted an EGT probe and will fit the gauge this weekend.
Unbelievable how much power the Pajero has now. I think I will use a lot less diesel and in two weeks time I will tow the Kavango again and will report back on the high temperatures experienced in the past going uphill.

[martinbo]

I am glad to report back, when towing the Kavango uphill, no more overheating. I tested the Pajero on the same hill that gave me a big fright last time. I applied full throttle until the EGT said 700 degrees and doing 118km/h, checked the heat gauge and it did not move from it's normal position.
Now I need your input, what is normal temperatures for the EGT?
Idling I get approx 200, cruising without the Kavango it varies between 350 and 450. Going uphill it goes to about 550 degrees.