P38 Cold Idle Issue

Datatek · Jun 18, 2020

Worth checking the UJ's, need to have a wheel off the ground when checking to unload the transmission.
If the DMF is breaking up, there will be a lot of black dust in the bell housing.

Nialox · Jun 18, 2020

Datatek said:
Worth checking the UJ's, need to have a wheel off the ground when checking to unload the transmission.
If the DMF is breaking up, there will be a lot of black dust in the bell housing.

Can I check for black dust?

Grrrrrr · Jun 19, 2020

Nialox said:
Can I check for black dust?

No panel on the bell-housing on the diesel. There are some little slots bit you'd need a small endoscope to get through. I don't think you're at that stage though.

If it was UJ I would expect it to be when propshaft spinning fast but anything is possible. It is certainly the cheapest and easiest fix so worth ruling out.

I am trying to think how to test the DMF without dropping the box. The DMF is, as the name suggests, in 2 halves with two long big springs inside to take up vibration. Over time these springs get tired and fail to absorb the vibration and leave the 2 halves slack. Usually there is about a tooth of movement and then you twist the flywheel with your hand and by the time you've moved maybe 3 teeth it won't go any further without moving as a single mass. When the springs are tired you can easily move over 3 teeth before it even gives some resistance but it still isn't a lot of movement when you consider all the resistance / slop in the gearbox, transfer box, VCU, UJs and diffs. One end is on the crank and we can get a spanner on the end of that easily enough. There's so much resistance though so I don't think you would notice when the springs start to exert pressure - or fail to. I'll see if I can find an old one in my shed and see if it inspires anything.

RangeRoller dt · Jun 19, 2020

Front UJ with me got worse until it starts to vibrate through the seat. Was apparent at tickover stationary, got real bad before I could identify it.

^^ he is right when you see it is slight play in new, worn is sloppy. There’s a vid somewhere by that nutty RRC guy - Britannica Restorations buy I cant find it

Grrrrrr · Jun 19, 2020

If you go down a steep hill only using the gears to hold her back does it sort of surge in fits and starts? Thinking Morse chain might be due replacement.

wammers · Jun 19, 2020

Grrrrrr said:
If you go down a steep hill only using the gears to hold her back does it sort of surge in fits and starts? Thinking Morse chain might be due replacement.

Can you replace that with a more modern Lewis chain?

Henry_b · Jun 19, 2020

wammers said:
Can you replace that with a more modern Lewis chain?

I don't think so..

I did one, the old one had gotten to a point of slapping the casing, evident by the damage inside and the horrible noise, the biggest pain in the ass is the chain doesn't have a master link so it isn't a case of dropping one off and putting a new 'un on..

You have to lift the Viscous coupling gear and the input shaft gear out, all of which are held in with C clips..

Hardest part is lifting them both out with one hand, ideally you need 2 sets of hands

Henry_b · Jun 19, 2020

Nialox said:
It’s almost like a shake. It shakes the whole car

It seems to be whenever you are one gear up
28-30mph in 4th for example.
With not much throttle action

whenever it’s under load from the engine it seems okay although I physically cannot go under 30 in 4th.

I don’t usually drive this way. But it’s a red flag and makes me think it shouldn’t happen.

I prefer to drive slightly higher in the rev range with less throttle.
I’m not a high gear chugger smashing down on the pedal at low rpm

Wear in the Morse chain is usually evident as a "chirrup" noise "especially on overrun" emanating from the passenger side footwell..

Drop it into 2nd and mash the throttle, if it is ****ed either it'll skip you'll feel and hear it..

Or it breaks..

50/50..

Datatek · Jun 19, 2020

Grrrrrr said:
No panel on the bell-housing on the diesel. There are some little slots bit you'd need a small endoscope to get through. I don't think you're at that stage though.

If it was UJ I would expect it to be when propshaft spinning fast but anything is possible. It is certainly the cheapest and easiest fix so worth ruling out.

I am trying to think how to test the DMF without dropping the box. The DMF is, as the name suggests, in 2 halves with two long big springs inside to take up vibration. Over time these springs get tired and fail to absorb the vibration and leave the 2 halves slack. Usually there is about a tooth of movement and then you twist the flywheel with your hand and by the time you've moved maybe 3 teeth it won't go any further without moving as a single mass. When the springs are tired you can easily move over 3 teeth before it even gives some resistance but it still isn't a lot of movement when you consider all the resistance / slop in the gearbox, transfer box, VCU, UJs and diffs. One end is on the crank and we can get a spanner on the end of that easily enough. There's so much resistance though so I don't think you would notice when the springs start to exert pressure - or fail to. I'll see if I can find an old one in my shed and see if it inspires anything.

Big springs in the DMF? Not seen many but they have been made with a composite material between the two parts much like the crank damper.

Henry_b · Jun 19, 2020

Datatek said:
Big springs in the DMF? Not seen many but they have been made with a composite material between the two parts much like the crank damper.

they have a large number of coils fitted in a semicircular orientation..

Datatek · Jun 19, 2020

Henry_b said:
they have a large number of coils fitted in a semicircular orientation..

Learn something every day. Sounds more reliable than the composite version.

Henry_b · Jun 19, 2020

Datatek said:
Learn something every day. Sounds more reliable than the composite version.

They last around 100 - 150k from the ones i've changed..

Datatek · Jun 19, 2020

Henry_b said:
They last around 100 - 150k from the ones i've changed..

I changed the composite one on my Transit at about 150K, the dust from the composite material knackered the starter motor. Fitted a solid replacement with a ,special clutch, £120 compared to €850 for a DMF.
The old flywheel has made a good nose weight for my little tractor

Henry_b · Jun 19, 2020

Datatek said:
I changed the composite one on my Transit at about 150K, the dust from the composite material knackered the starter motor. Fitted a solid replacement with a ,special clutch, £120 compared to €850 for a DMF.
The old flywheel has made a good nose weight for my little tractor

I too tend to fit SMF's where i can..

Many a mondeo MK3 Duratorque are running around with new SMF flywheels

They do indeed make good nose weights for my tractors too

Mark Piercy · Jun 19, 2020

wammers said:
Can you replace that with a more modern Lewis chain?

RangeRoller dt · Jun 19, 2020

So what is the significant difference between Morse / Lewis chains?

Datatek · Jun 19, 2020

RangeRoller dt said:
So what is the significant difference between Morse / Lewis chains?

I think the joke went over your head

RangeRoller dt · Jun 19, 2020

Ah

Only one is in a jag

wammers · Jun 19, 2020

Mark Piercy said:
View attachment 212652

Took a while.

Mark Piercy · Jun 20, 2020

RangeRoller dt said:
So what is the significant difference between Morse / Lewis chains?

One is a grumpy fecker and the other à stupid ass!!

P38 Cold Idle Issue

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