300TDI cruise control.....or not!

Still getting used to my disco and trying to suss out what all the buttons do ( didn't come with a manual (not that I would read it anyway as I'm a proper bloke))

Heard about this cruise thingy mi bob so thought I'd give it a whirl....
On motor way.... Press button with bridge symbol on.... Light came on.
Got up to speed 70ish..... Press button on left of steering wheel (set).
Take foot off accelerator..... Car gradually slows down!!!

So I take it my cruise control isn't working!

Any tips on where to start looking... Really would like to try fix this myself as opposed to drop it of with man in overalls and oily rag

There's one or two threads on this topic that have come up in the past.
The favourite seems to be checking the vac hoses haven't split at the unions in the engine bay. You can either renew them or the cheap 'n cheerful way is to snip them off at the unions where they split and re-attach.

That's the first thing to check in any case.

Cheers,

JC.

Leaking vacuum-hose is common and the simplest problem to fix, so check the hose and where it joins the vac pump, throttle actuator and brake and clutch peddle switches. I have finally had to replace the hose after making repairs to it over the last 15 years.

Was the vac hose on mine, I cut it down shorter as it was at the ends that was perished

MGBGTV8 said:

There's one or two threads on this topic that have come up in the past.
The favourite seems to be checking the vac hoses hasn't split at the unions in the engine bay. You can either renew them or the cheap 'n cheerful way is to snip them off at the unions where they split and re-attach.

That's the first thing to check in any case.

Cheers,

JC.

Click to expand...

Ok..... Where's the engine bay (joke...it's that big bit at the front)
Where in the bay do I need to be looking for this vacuumed pipe.... don't have a Haynes either

If u can't suss out the bits & bobs in your engine bay then u really do need a "man in overalls and oily rag".

Well I recognise some of the bits... But it's bigger .... Last lump I played with was a flat 4!!

Bomber785 said:

Well I recognise some of the bits... But it's bigger .... Last lump I played with was a flat 4!!

Click to expand...

Start at the beginning, that's at the CC vacuum-pump which can be seen in one of the large holes under the jack position in the engine bay and then follow the black hose.

discool said:

Start at the beginning, that's at the CC vacuum-pump which can be seen in one of the large holes under the jack position in the engine bay and then follow the black hose.

Click to expand...

Thanks..... That will be a task for the morrow

Mine did the same, totally replaced vacuum hose.
Cost less than a tenner, and now works with no issues.... :-

I had to replaced a 2M length a few weeks ago using 5mm silicone vac hose, only £4.54 from e-bay, now that will be fit and forget

Found the hose has split at the vacuum thing under where the jack lives, was a bit concerned to find the unit was just wobbling around and not fixed to anything!

Cut the hose and re attached, not had chance to try the cruse control yet.

next job is to look at the hoses that run across the top of the engine bay... think its the screen wash and there is a T piece in it near the fuel filter

Bomber785 said:

Found the hose has split at the vacuum thing under where the jack lives, was a bit concerned to find the unit was just wobbling around and not fixed to anything!

Cut the hose and re attached, not had chance to try the cruse control yet.

next job is to look at the hoses that run across the top of the engine bay... think its the screen wash and there is a T piece in it near the fuel filter

Click to expand...

Unit should be bolted to the inner wing ...

Bomber785 said:

Found the hose has split at the vacuum thing under where the jack lives, was a bit concerned to find the unit was just wobbling around and not fixed to anything!

Cut the hose and re attached, not had chance to try the cruse control yet.

next job is to look at the hoses that run across the top of the engine bay... think its the screen wash and there is a T piece in it near the fuel filter

Click to expand...

That "thing" is the vacuum pump and it's mounted on rubber grommets and accessed via that hole in the panel below the jack, looks like some one else has been there.

discool said:

That "thing" is the vacuum pump and it's mounted on rubber grommets and accessed via that hole in the panel below the jack, looks like some one else has been there.

Click to expand...

Ok next job re mount the vacuum pump!!

I have the same problem. My confusion is. I can only see reference to one vacuum hose from the pump to the actuator so why the T pieces?
Where else do the pipes run or could I replace it with just one continuous pipe from pump to actuator?

dilligat said:

I have the same problem. My confusion is. I can only see reference to one vacuum hose from the pump to the actuator so why the T pieces?
Where else do the pipes run or could I replace it with just one continuous pipe from pump to actuator?

Click to expand...

Yes you could but I wouldn't. The T piece is to extend the hose to the clutch and brake peddle which will dump the vacuum when operated .

Oh I see so the clutch and brake pedal switches mentioned are dump valves and not electrical switches?

EDIT

I've found my copy of Rave and see they act as both. Aha eureka moment!! Right time to find pipe and replace.
What length/diameter will I need?

Thanks

dilligat said:

Oh I see so the clutch and brake pedal switches mentioned are dump valves and not electrical switches?

EDIT

I've found my copy of Rave and see they act as both. Aha eureka moment!! Right time to find pipe and replace.
What length/diameter will I need?

Thanks

Click to expand...

Yup electrical as in telling the ecu to cut 12v power to the pump, and the hose is 5mm I/D and around 2.5 to 3M.

I have some pictures of where the hoses are here

My Land Rover Discovery 1 300TDI, overland preparation and blog: Discovery 1 300TDI Cruise Control not working