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Only a minor problem with my cruise control on my 2001 4.6.

Cruise control is working but if for instance I set it at 50 mph it slowly drops down three or four mph and usually stays there occasionally going up one or two mph.

When I got the car this was always stable.

Is there anything that can be done or is this just a little annoying?

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Sounds like a cracked vacuum rube which is leaking but has not yet given up entirely. Favourite places to go are the by the connections to the actuator/diaphragm or where the vacuum tube exits the firewall into the engine compartment and just behind the engine. The cracking will be evident on inspection. If so just renew the vacuum tube - I used reinforced tubing on mine so it lasts longer.

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Thanks for that. I will be onto that tomorrow.

Excellent if it is as easy as that.

Cheers.

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99% of cruise control problems are down to splits in the vacuum pipes. Easy check is to pull the pipe off the Tee and see if you can blow down it. If you can, that's why the cruise doesn't work.

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Split found, cruise working perfectly again.

Thanks guys!

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Where does the vacuum tube run? I need to replace mine as it has split so many times it's now too short and I think that has caused it to wear on the firewall.
I'd like to tape one end of the new one onto the end of the old one and pull it round but that's a bit of a non started if you can only find one end :D

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Across the bulkhead behind the engine, through a hole in the bulkhead and comes out next to the steering column and loops around to the brake pedal. Easiest way to do it is to take the instrument cluster out and go in through the hole. Two person job though as it is a nice tight fit through the grommet in the bulkhead so you need one person inside and one outside to help it through.

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It runs from the T by the actuator along the firewall behind the engine and then goes through the firewall in line with the brake pedal and terminates in a ‘switch cum valve’ operated by the brake pedal. Access is pretty tight under the dash above the air ducting from the right hand blower motor but it can be done but be careful as the plastic of the switch can be brittle and it’s locating lugs easily broken when trying to get the vacuum tube off and on it.

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Yes, I cannot stress enough to be extremely careful around that damn switch, I've broken two the two times I had to manouver with the damn vacuum pipe.
I suggest also to fit reinforced or silicon so you can write that off the list of troubles instead of being a regular occurrence ... especially if the brake switch goes along with it (and you lose ABS and ETC as well).

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I’ve only broken one switch! I used reinforced silicon tubing for the full belt and braces approach! It’s outer diameter is slightly bigger than OEM but it goes through the firewall grommet OK but is tighter to fit on the infamous switch due to the proximity of everything else. I ended up removing the ducting to get it fitted/located and then had to be very careful putting the ducting back.

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Yes, and - feel free to make fun of me - since I have not put the ducting back I am suffering the summer heat lol

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Well, that job sounds like a real bundle of laughs!
Thanks though :)

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The one part of the hose that doesn't perish and split is the bit under the dash, probably because it doesn't get exposed to the same amount of heat as the section under the bonnet. Rather than risk breaking the brake pedal switch or it's mounting, I've cut the pipe about 6 inches from the switch, used a joiner and fitted new pipe from there. All you are doing then is dealing with getting the pipe through the grommet.

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Gilbertd wrote:

Two person job though as it is a nice tight fit through the grommet in the bulkhead so you need one person inside and one outside to help it through.

I have to thread wires through tight bulkhead grommets often, usually by taping to something stiff like a long 5mm drill bit, bit of 6mm copper pipe or brake pipe. Just had a ball-ache doing it on a Porsche Cayenne turbo, mostly because I'd forgotten where the bulkhead grommets were.

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Richard, that is so darn clever, brilliant and simple. You make me feel like I haven't employed any brain cells at all on the matter ...
Using a splitter in the pipe means also you have less stuff to worry about besides the switch, like the ducting, which is a bother on the way.
I feel elated :-)

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Lpgc wrote:

Gilbertd wrote:

Two person job though as it is a nice tight fit through the grommet in the bulkhead so you need one person inside and one outside to help it through.

I have to thread wires through tight bulkhead grommets often, usually by taping to something stiff like a long 5mm drill bit, bit of 6mm copper pipe or brake pipe. Just had a ball-ache doing it on a Porsche Cayenne turbo, mostly because I'd forgotten where the bulkhead grommets were.

I have to do similar bits at work (not car related, IT in this case) and have found that plastic plumbing pipe works very well. The best stuff is either the tiny pipe used for postmix in Pubs (the soft drinks guns) or the pipe they use for the Beer gases, the later being stiff enough to pass through void spaces where you can't get access to both sides of the hole you need to use. Postmix pipe being much smaller would work well for going through bulkheads for LPG control panel wires.