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Old 31-05-2010
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Deezelweazel  Deezelweazel is offline
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Exclamation Myths and fairy tails about the VM TD

After reading some myths, and fairy tails about the reliability aboiut the VM 2.5 Diesel engine and seeing people spending hard earned money on gadgets that are virtually worthless I think it's time for some basic knowledge.

If you are the person thinking knowing all wisdom about this engine stop reading...

After doing a bit research (the last 2 years), talking to the biggest engine rebuilding manufacturers and discuss the abilities with internal combustion engineers I found several reason leading to engine fail.

It all started with chasing failed engine heads and searching for the causes.

after finding out that most people are not informed how to behave with a "modern" Diesel engine I think we should start here.

1) This engine is extreme cold start sensitive!

Construction of this engine is unique and advanced at its time. The crank bearings are embedded in a circular alloy case.

Due to the reason that alloy and iron have different heat expansion rates they move until they reached proper operating temperatures!

The same goes for the single heads. The heads move until proper clamping force is reached by operating temperatures. If you hit the pedal in this time frame you ask for trouble. Reaching water op temps is no indicator for operating temps. Oil temperature is the proper indicator for that! If you drive without obeying this- blown head gaskets...

The oil pump is located in the front of the engine the suction head is in the rear in the oil sump, of course. Most of you don't recognize the time which is needed to built up oil presure- which is long compared to other engines( have in mind we talk about seconds- but for bearings this is long!)
Add a cheap oil filter with a faulty or cheap or in the worst case without anti drain back valve and you spin the engine bearings dry.

Idle the engine until proper oil pressure is reached!

Bores wear at an alarming rate,as do the pistons /wedge compression rings, if the oil isn't changed regularly and the engine driven 'hard'.

Camshafts wear, due to the high loads,2:1 rocker ratio, the rocker arms are the same as well as the rocker shafts.

The bottom end however is nearly bomb proof, providing the front main bearing doesn't turn in its bore.

All heads need to be bolted down on a jig and done at the same time rather than each individual head as is commonly done. Lining them up to the gasket and the block is extremly important as partially covering holes leads to failure.

If you can't afford a good oil and filter and a frequent change within the interval, do not drive a Diesel.

2) The cooling system

Head cracks develop between the valves and at the side of the heads were are no water cooling gallerys.
The engine is tilted upwards towards the front that causes the air being caught in the front of the heads, causing hot spots.
Engine coolant must be refilled while the rear of the Jeep is on a ramp or you have access on a vaccum coolant refill. Otherwise you ask for trouble.

Stop playing around with electric fans- trucks and semis around the world go with visco fans for a reason- huge airflow and being effective. Now you think an electric fan is the solution?
I've seen electric fans being used without a proper build fan shroud.
Do you know what a laminar short is?
So you play in the mud, do you? Did you ever recognized that the front of the visco fan is actuated by a temperature sensitive spring?
Cover that spring with mud and dirt and wonder why it doesn't work right?
A Brass brush works wonder on your fan front- just give it a try.

Stop your cheap tries to improve cooling. Your Jeeps are at least ten years old. You have to bite the expensive apple and to replace that cooling system.
I would call myself extremly careful with the cooling system.
But I got a tablespoon of dirt out of the engine,while cleaning the heater core.
I found a layer of thin grease inside the engine which required aggressive cleaning. Voila engine temps respond quicker to fan activity.

If you can't afford this- don't buy a Diesel!

Do you know why the factory radiator is made of brass / copper and not of alloy? Because of the much better heat transfer of copper. That makes the radiator expensive, of course.

To be continued...,

but I'm keen to listen to response and thoughts so far.
Please don't tell me your electric fan is so good-it's boring to listen to that.
It has a reason why every serious military truck uses the visco fan.
You can have the biggest airflow which is useless if you have no heat transfer or restricted flow...