Td5 holding revs on gear change

109inches · Jun 20, 2020

Evening all,
Quick question, my manual td5 discovery has always held onto revs on changing gear and is always more noticeable the more you use the Rev range when in a gear.
I’ve done some searching on this topic and it has always pointed to the clutch pressure switch on the master cylinder. Now mine is missing as it had a new master cylinder put in before I purchased however all the threads I’ve read on this say the cruise control should not work if this switch is missing or faulty. Yet my cruise works perfectly.
Just looking for clarity on the truth behind the link between that switch and cruise control or if there’s another switch on the pedal that controls it and would buying a fitting a switch for the master cylinder solve my revving issue?

Thanks

NPG · Jun 21, 2020

The clutch switch is the only mechanism there is that prevents engine surge during gear change. If yours is a facelift model, it should be integrated with the master cylinder. Otherwise it would be a separate unit on the RHS of the engine bay. Something tells me you have a facelift model but with a new pre-facelift master cylinder and a bridge between the pins on the clutch switch connector. This would force the ECM to think the clutch pedal is in the rest position so it could operate the cruise control. You can test this by checking if cruise control cuts off once you press the clutch pedal.

109inches · Jun 21, 2020

Yes it is a facelift model. I can feel underneath the master cylinder there is an Allen key or torx bung plug where it should screw in.
From other threads I was reading I was under the impression the cruise would not work at all if unplugged?
I’ve checked the connector and it has not been bridged at all.

NPG · Jun 21, 2020

109inches said:
Yes it is a facelift model. I can feel underneath the master cylinder there is an Allen key or torx bung plug where it should screw in.
From other threads I was reading I was under the impression the cruise would not work at all if unplugged?
I’ve checked the connector and it has not been bridged at all.

Mine is a pre-facelift model so any comparison would be slightly off. But if cruise control cuts out once you press the clutch pedal, this would either be the master cylinder switch or a clutch pedal switch. You will need to confirm if this is the case as I cannot think of any other ECM input that keeps track of the clutch pedal.

Landmark2 · Jun 21, 2020

stc000280-clutch-master-cylinder-for-discovery-2-td5-doesn-t-fit-v8-ap-driveline-oem-equipment.jpg

This is what it should look like for the facelift model

109inches · Jun 21, 2020

Ok so mine has been fitted with a pre facelift master cylinder if that’s the case. So in what location is the switch located?

sierrafery · Jun 21, 2020

here it is, it should be a hole for it under that plastic plug on your's, the cruise control works if it's unplugged but no surge damping

109inches · Jun 21, 2020

Ok great I’ll get one ordered
Thanks

sierrafery · Jun 21, 2020

Order MSK500020 cos some suppliers are listing the 500010 as for D2 but that's not good, it's a difference between the D2 and Defender switches even though they list them as good for both

NPG · Jun 21, 2020

[QUOTE="sierrafery, post: 4905161, member: 9153"... the cruise control works if it's unplugged but no surge damping[/QUOTE]

Are you sure about that ? Personally never tested it but since it's a NC switch, wouldn't an open circuit disable cruise control ?

sierrafery · Jun 21, 2020

It's a whole mess around the Td5 clutch switch and when it comes to D2 the description in RAVE is wrong while the diagram is correct which shows it N/O(as it is) and closes to earth when the pedal is depressed that's why the cruise control can work with it unplugged cos it's like when the clutch is not touched while if the switch fails to close to earth there is no surge damping, bridging the pins in the plug will cure the surge on gear change but the engine will run with less power...the section in red is not valid for manuals:

here's a more accurate(though not 100% correct) description from LR Technical Academy(whole doc attached)

NPG · Jun 22, 2020

sierrafery said:
It's a whole mess around the Td5 clutch switch and when it comes to D2 the description in RAVE is wrong while the diagram is correct which shows it N/O(as it is)

Many thanks SF. Yes, that diagram does attest to what you're saying and that it's a NO and not a NC switch. One would have thought that a fail safe design would require a normally closed circuit so the ECM could at least detect a circuit failure and disable the cruise control function for safety reasons.

Cheers

Td5 holding revs on gear change

109inches

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109inches

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