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...:rolleyes:

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.

http://up.picr.de/4471816.jpg

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...

Good read, well worth sticky for TD drivers of any Jeep.

Excellent post.

No problem with the machinery, it is always user error.

all the above reasons why the VM makes a great boat anchor/ i mean engine:rolleyes:

there must be a few things to spend money on to better the useability of these things. Unfortunately all the above displays is the motors italian heritage.
how come they couldn't have maybe included a wally factor like the patrol 4.2 diesels?

Kudos on the oil filter etc.
i am not slagging xj diesels, i sought one out, but compared to the 4.0 pet.......

i know which one will be more likely to get me home

Yeah, all of the details above are why anyone who wants to spend time driving and enjoying their jeep not mainaining and babying a temperamental piece of Italian engineering should NEVER consider a diesel XJ.
Stick with the 4.Oh!

I totaly agree with Deezelweazel.
If it comes to think of it a car is designed by hundreds of engineers and thay
pretty much know what is needed to make a car as reliable as possible to be
able to put it on the market.
Cheers,
Andrei

Hehehe, the complete story is to proof the reliability, if you bite the (expensive) forbidden fruit.
The Diesels are nice, if you do your homework. If not, they will turn into a neverending nightmare and construction site( ...or a boat anchor, hahaha).

I have invested so much money that I can't simply turn back.
Instead of seeking for solutions to extend engine life, you must seek for causes.

Eliminating causes are the best way.
What do you do when stuck in the mud? Changing back to street tires? No, you upgrade to Boggers!

But to play sucessfully- you have to return to the Diesel roots and know the special needs of a Diesel.

I'm going to pick on the vintage iron gasser engine layout, when done here.:mrgreen:
By the way, who is telling the old fairy tale about being used as a boat engine? Engine design is not made as a cold running engine. As can be seen on the alloy bearing carrier rings.
This engine was used with great reliability and success in austrian agricultural machines(Reform)under heavy load conditions.
Engine setup is different. Lower charger pressure and different cooling layout with a much lower red zone.

Did anyone recognized the manipulated engine coolant temperature display? It stays locked around 90° to 100°- in case of overheating the needle jumps suddenly to the red zone! This is not possible with a linear reading meter.

Read somewhere ages ago that car manufacturers won't fit linear gauges coz they create unrest -- ppl just don't like seeing that needle creep. So they actually forced some poor engineer to deliberately create gauges that act like a indicator light. You might as well have a light on the dash that glows red when there's trouble. (Come to think that's exactly what my old HQ holden did have :D)

Don't know if it's true or not....

Some modern cars I've driven have no temp gauge, they have a red light for overheating, and some of them have a blue light for not warmed up yet :roll:

I always struggle with how long to warm an engine up. My manual clearly states not to idle for more than 5 minutes as this contributes to glazing. It also says to idle for 1 minute to lube the turbo before driving. I wait the minute and then drive reasonably until the water guage reads normal and then I just drive normal. However driving reasonably seems to lag the engine more. Is there a good choice?

vk2icj I'd go on the long side of 1 minute, and then drive without labouring the engine. Normal driving within the warm up period is okay, particularly in a 4WD where torque is delivered down low. The key is not to thrash it during warm up.

Idle is very important- but the main reason is to supply the turbocharger with oil. Because the charger is a supplemental external device and the last unit which receives oil.
Don't idle longer than necessary- EGR opens during partial load(including idle) and soot builds up quickly in the intake. I had to scrape out 3-5mm of soot after 100k.
But anything longer than a minute during cold conditions is waste of Diesel.

The shut down prodedure is even more important. You would be amazed to see engine temperatures climbing after shut down!

Water temperature may be ok-but oil temperature will be at a safe operating temperature after the double distance- if you drive without load!

sorry about the boat engine thingy, this thread is titled "myths and fairytails...";) i am adamant that it would still make a good boat anchor if it breaks:mad:

perhaps the engineers should have spent more time modifying the block?
agricultural use in Austria is hardly stop start conditions in an Australian summer.

Deez, would copper head gaskets and a really good low viscosity synthetic oil (changed at same regular intervals) go some way to prevent the VM's dramas?

the toyota boys (in the earlier model 3.0l supras) claim an elimination of blown gaskets while still allowing the head to 'wander'.

and todays modern full synthetics have far greater lubricity at a greater range of temps. they have a lower viscosity for a given application, lubricating internals sooner and evenly spreading heat better.

There's no wally factor on the patrol 4.2 diesel.

The only reason it lasts so long and appears so bulletproof is because it doesn't generate enough power to hurt itself. low boost, low combustion temps and immense exhaust emissions which is why it NEVER saw use in europe.

If you overheat a TD42 you will hurt it same as any other motor. And yes, the TD42 has a very nasty habit of running too warm, there'd have to be hundreds of threads on the internet about it and hundreds of mechanics who reckon they can fix it.

It might be less temperamental than the VM 2.5 in the XJ but there's a big difference in basic design and intended use.

It's all good, bud
-over here they think in fact it is a boat engine,hehehe.

no, copper is simply to soft. You can o-ring the head gasket, but that is race tech and not really cheap, because it's not an ordinary o-ring. It's a nitrogen filled ring and the heads have to be prepared for that.


the "wander" is what kills your head gaskets- because you have 4 of them and pressure of a Diesel is way higher than a gasser- it will "lift" your heads
To prevent that, I switched to ARP studs- the original bolts have to much stretch.
As I already said: the fun gets expensive...

The Synthetic oil has better heat carrier abilities.
I use Mobil1 TurboDiesel 0 W40 during the summer and Mobil 1 Delvac 5W40 in the winter, I can afford to buy it, because I got cheaper 60l drums.
More is less expensive. It is still overkill and I had to reseal the complete engine- it started to drip everywhere.

Be warned!
Before you can use that thin viscosity you have to check bearing tolerances. If the crank is worn out already you get a real dangerous pressure drop!
Rebuilding is questionable.

But you still have to get rid of the oil heat.
The water/oil cooler is not enough to provide sufficient cooling. It also brings heat back into the water circuit- not good at all.

I use an additional oil cooler with 500cm². That seems to be huge, but it is only 10cm by 50cm- BMW uses the same size in their 2.5 Diesels.

Interesting read, it will be interesting to hear what will be said of the humble 4.0 litre petrol....

Wow, 60 litres of mobil 1? That must cost a fortune!!

heh heh ....

I'm thinking the "humble 4.0l petrol" might survive the blitzkrieg but its cooling system might not. ;)


Good stuff deezelweazel .... keep it coming ..... :mrgreen:

i use cat deo in mine

@davesta:
That's what I thought too, but it's less than 50% (320€ incl. tax)compared with a single liter.
Maybe mil. discount does play a role, too.;)
Trust me, I couldn't afford it otherwise.
My first thought was it might be to thin- and I expected rattle of the hydraulic valve lifters but after checking clearances it is ok- not more noise than usual.
It does help while starting.

Maybe you are going to ask why is he using a thicker oil during the winter? Simple explanation: I try to avoid use during winter. Salt on the road is to aggressive. So it's parked the most time in a garage.
Just trying to cut the corners with "cheaper" oil during storage.

@murray: Isn't cat deo an ACEA E5 oil? Good stuff, must be horrible expensive as all CAT stuff.


But after all oil is not the problem in this engine. The oil circuit can and must be used as an additional cooling aid take take off the heat load of the coolant cuirciut!
Do not remove the built in water/ oil cooler. It isn't a real help to get heat out of the engine bcause the heat of the oil is transferred back to the poor coolant layout.
It does help to warm up the oil during cold start.

Remember first heat law: Heat is always transferred from the hot medium to the cold, never vice versa.

You must grab for every advantage you get:
most people don't know:
A silver radiator surface has only 90% of the heat transfer capability of a black one.
So which one are you going to choose the next time? An alloy radiator?
You are just wasting 10% heat transfer...

You can't afford waste of heat transfer, if you want to drive that Diesel!

Do not replace the stock water pump with trick or high flow units. Just make sure it is in good working condition.
High flow also means a short heat transfer time in the radiator. That results in higher heat preload as the coolant comes back into the engine.
This rule is also transferrable for the gasser. ( By the way: It also consumes a lot of hp!)
The second dangerous thing about it is cavitation. The coolant pump starts to add air bubbles at high speeds. Here we go again- bubbles are big trouble.

You don't believe that?
Get a water pump for the electric drill and attach some clear plastic hoses and start to pump water- 1.try: low speed, 2.try: high speed
ups, were do those bubbles come from during high speed?
Caviation!

Do not decrease the amount of coolant- it is also lubricant for the waterpump!
The coolant circuit does contain a lot of different materials.Copper, brass, iron and alloy- not really an ideal combination.
So make sure to keep the coolant fresh- it does also contain corrosion inhibitors.
You need them!

Flush your coolant system! You need an aggressive acid to get rid of the dirt! I already mentioned it, I got a tablespoon of dirt out of the heater only!! It does work afterwards! It is also a welcomed aid during high load conditions. If the needle climbs into the red zone, turn on your heater- you need every assistance you can get.
Windows can be pulled down, by the way...

Do not obsruct airflow to the radiator. I know about the cool bars and aux lights in front of the radiator. They are an absolute nono!
Just have a look at the FSM. It is also mentioned in them.
They do not write it for fun!

What do you think about using white vinegar as a cooling system flush? I've seen it mentioned a couple of times on naxja... (i don't actually own a diesel, just curious in general...)

i also use cat elc top stuff

@davesta:
every sort of vinegar works- you need to leave it the coolant circuit over night. alloy may get a bit dull but that doesn't matter at all.
I used household cleaners with great success like antikal- they contain sulfur acid wich kills a lot of grime.
The heater is copper clean inside now. I let it in the coolant circuit over night-it does not work on the grease slime inside the engine. But drano works good there, hehehe

@murray:
You just convinced me to use that CAT stuff.
If it works in their engines it will work in our diesels too!
The data sheet has remarkable abilities and it does contain already deionized water.

I tought about Evans waterless coolant, but what to do if you need to refill while travelling?
I just have to find out were to get CAT elc...
CAT engines are designed to give fullpower all day long-so it must be good stuff.

Just found out, it is designed for wet sleeve cylinder liners.
That the absolute right stuff for our engines! Good find, Murray!
Do you work with CAT equipment?

i have worke for the west australian cat dealer since 1986
cat elc is the best coolant i have ever seen
seen thermqstat housing on desiel forlifts had it in ther system 5 years still lok brand new
you in germany? zepplin is the cat dealer

Cool Murray, thank you very much for the info. I bet you know about your job and I won't go cheap here.
It is essential to have the best affordable coolant! No doubt about that. and I'm sure Australia can get a bit sunny!!!

I just replaced my thermostat, it had the worn scratch marks in the wax chamber again. I don't waste my heads for a 9 € thermostat.

It took a lot of scrubbing to getrid of at least the visible dirt inside the engine.
A rifle bore cleaner and several bottle cleaners are good to use for that. Chemicals alone are always difficult. they simply can't replace a good brush.
So a good coolant is very important. And access to a better one is extremly valuable.

I can't wait for the words of wisdom on the 4.0!!!!
When is it going to start????

stop bringing up anything to do with the bloody petrol and leave personal opinions out of the thread FFS. The OP has created a thread designed for diesel owners to discuss the issues they have and prevention/cures - let them be.

I took Murrays advice. The elc is fantastic! How much is the CAT oil Murray?

it well priced

what r the worn scratch marks in the thermo wax chamber? what do they mean?

They don't mean a lot...
They simply mean it's worn out and the valve can be sticky open or do not open as demanded.
The slight angle, caused by the worn marks, can stop to open it- which leads to engine overheat.

Just keep an eye on those things- hey, after ten years of use things do wear out.
Grabbed the thermostat out of the trash to show you:
The wax expansion chamber is located in the middle.
It is a brass tubing. Can you see the shiny brass part? Thats the worn mark- the rest of the chamber is dark due to oxidation which also means coolant was depleated in the past.
This little mark can prevent proper opening of the thermostat.

http://up.picr.de/4485584.jpg

Credit to everyone, especially deezelweazel. Interesting read. The tips are excellent for modern diesels and put a good perspective on things. Thanks!

Thanks for everyone keeping this thread interesting!

We also have to look at the hoses.

Try to develop some routine inspection- there is nothing wrong with it.
If your friends laugh, let them laugh.
Every pilot inspects his plane for take off- I inspect Radar sets every morning before I activate them from standby to radiate. Failure can cost lives and health.
A hose is easy to replace, heads are costly...

Check them everytime you look into your engine bay!
How do they feel? Don't laugh- it is a real good indicator:
- to soft- not good
- hard and stiff- not good
Check them for being brittle and cracks while squeezing them
replace them as soon as possible if they get bulgy- failure is right to be expected!
I use Armor All with great sucess to keep them flexible.

Do youself a favour and change faulty hoses before you hit the road!
It is asking for trouble!
Do also check the underside of your hoses.
Keep them clean of mud! You want to see difficulties, won't you?
Do not experiment with hose bandages- replace the hoses in advance.

There is no need for Chrysler parts. Ask your hydraulic specialists- they do carry also coolant hoses for the fraction of the Chrysler costs.

One thing I really hate to see on engines coolant hoses are those worm gear clamps.
a)They cut into the rubber( the cheap factory clamps do that too !)
b) They are not able to hold clamping force safely!

Use t-clamps like this:

http://up.picr.de/4487040.jpg

http://s1.up.picr.de/4487041.jpg

The reason is (again) simple:
- they do not loosen themselves
- they are easy to loosen with tools even in tight spaces
- they have a consistent pressure on the hose without weakening it
(did you ever get one of those snapping spring clamps to the tip of your fingernails?)
- they are cheaper than original from Chrysler
- stainless steel( but lube the threads with anti-seize to keep them in working condition!)
- do look good ;-)
I use them on the intercooler hoses too- no more oil leaks and drips in the driveway!

deezelweazel, thanks for the info on th thermo, thanks for the start of this thread.I weekly look over the xj, looking for anything that looks out of place. I actually like doing that, tht way I get total mission reliability.
Im thinking of fitting the tj 6 speed in to the xj. what do u think?
Also why do the engines get oil in the intercoolers?

a 6 spped tranny:
You won't gain any benefits from that
- no better mpg
- no higher top speed

engine max efficiency is calculated at 93Km/h-95km/h, any higher speed will consume to much fuel with the 3.73 gearing.( stock tires, max 235/75R15)

Oil in the inintercooler
This happens (and is normal!) when boost pressure isn't high enough to seal the compressor wheel against the turbo housing. A small amount of oil will find its way into the intercooler.
Another possible way is the crankcase ventilation. You shouln't be worry about this if it is less than some drops and as long as you will not recognize an oil level loss.
To much oil in the PCV is an alarm signal!! Either your turbo oil drain is plugged or restricted or blow-by is too high. Time to check the air filter too!
A lot of blow-by indicates worn pistons rings and neglected oilchanges in the past as already mentioned in the begining.

This crankcase ventilation oil is used as an example in early VW Turbo Diesel engines to lube the intake valve( a diesel has no intake valve lubrication otherwise)
not a bad idea at all. It becomes worse in combination with the EGR! Oil and soot builds up a sticky goey glue in the intake.
Just have a look at this intake ellbow:

http://up.picr.de/4492916.jpg

Soot and oil as a combination are terrible there is a layer 3-5mm thick.
You can imagine what that does to your engine performance. The engine starves for air. Air starving does mean high EGT's. High EGT's aren't good for your head at all.
What can you do to avoid oil in the intake?
Avoid extended idle or city stop-n-go.
Or install an oil trap can into the PCV tubing. You won't be able to supress oil leaking from the turbo- it won't matter at all, if it gets into the chamber it will be burned safely.
I do worry about EGR soot. An EGR delete is the thing to do.
Don't worry about higher combustion temperatures. EGR is only active during partial load.
It dillutes the intake air with 7% exhaust gasses. This will take out( yes, you read correct!!) combustion heat of the combustion process and reducing emissons.

Closing EGR is not allowed due to environment protection...think of that what you want to think about it.
We have a strict emisson control called safety inspection and the emissons reader does not get the delete.
Don't worry about a engine failure light. It has no connection to the delete it if you do it without interfere electronics.

What are the benefits of EGR delete?
Some claim less fuel consumption, I didn't...
Some claim a better part throttle response. I didn't...
Some claim more power. I didn't...

No soot in the intake. YES! That's enough for me...
@dgrn1708erin:
I hope that answers your question, if you have further questions feel free to ask.
You can't get 100% reliabilty by a visual check. You need more like extra gauges, and checks like yearly compression and injector ( spray pattern, pressure build up, release pressure)
If you want more to know about that, take the time and begin to start to read the FSM manual for your model year. There are a lot of service procedures and tests in it to keep you busy.

What are your thoughts on water injection?

Where it is introduced as a mist into the air intake. Some claim an increase in economy and performance - plus cleaning effects (used quite extensively with vegetable oil on other engines - normaly direct injection where they can suffer from ring gumming with veg oi, but the water clears it)

With the soot/oil build up it is shocking how quick it builds up. I changed some exhaust gaskets and cleaned the intake, 2 weeks later (when head gasket was being changed as that had gone - as well as exhaust manifold gaskets) - it needed cleaning out again

and I would recommend cleaning the intercooler out - shocking what a difference it makes

I can tell you a bit:

It does work, but those tiny pumps are way overpriced. you need really good pressure- such as a pressure washer with about 1200psi or higher. I've seen such a build up, looks strange but works.
I will seek for some pictures( I still have them somwhere)
The more methanol you add, the more power you gain.

The difficulty is to reduce head temperature constantly. That can only be obtained with a different setup.

An increase in economy ? I doubt that, the unit istelf is way to expensive to get any savings back.

The use of Bio Diesel is strictly forbidden with an XJ.
I wouldn't risk the mixture of veggie.
An overhaul of a leaking pump is expensive. The VP 37 does not like it at all.
In the intercooler can't be any soot- only oil. A sharp ride cleans that out.
you are right- the difference can be noticed.

I am surprised by this - as in the UK it is considered one of the best set ups to run veg oil on a single tank system - an IDI engine and the Bosch mechanical pump. It is rated the same as the old Merc engines and runs 90/100% veg in summer (about 80% winter).

I've done about 30K miles on veg - some freinds have done about 70K (in the UK you are allowed to use 2500L of veg without paying fuel duty - and there is no VAT as it is food)

The savings can be huge. Diesel has just been around £1.20/L, I've just stocked up on 480L of oil at £0.42/L (offer at a supermarket - buy one get one free).