Thread: retro fitting factory cruise to a 1998 300 TDI disco

I suppose the best place to start this is to go through the process item by item. I am not a mechanic and although I did this myself I did have plenty of guidance from the more knowledgable disco owners.

the easy stuff:

the dash cruise control enable/disable switch is the same in all variants so scavenge one from a V8 - there's plenty around. you will need the fine hands of a six year old to find the wiring to plug it in though. I found mine taped to the loom right up high and, even with the dash fascia panel removed it took aulro member Taffy to physically show me the plug before I could find it (he had a loom removed from a car). once found - easy plug it in!

the vacuum pump lives below the jack under the panel which would support a second batrtery if you have one. As far as I can tell there is only one pump for v8s or diesels although I'm sure there must be a different pump as the spring pressure on the injection pump makes the speed take up very slow and on mine it only works well when you set up your speed and THEN turn the cruise on. One of you disco experts may help us all here!
The loom and plug for the pump connection lives near by and is below your power steering hoses. A short branch comes out of the loom with a square section 3 pin plug for the connection and of course you'll need some vacuum line. (once again thanks Taffy for showing me this plug)

My car has driver's air bag (you'll find this is important later) and so the little set/resume switch for the steering wheel is the same for all variants with SRS and just plugs in (you'll have to make a little slot in the soft rubber wheel surround to feed the switch through but it bolts and plugs up to existing brackets and plugs.

The ECU is diesel only (the v8 is AMR 1173 and the diesel AMR 5441) this plugs into the existing loom behind your glovebox - easy access and plugs and bolts up no drama - I actually found this plug myself !! Check out UK ebay as these come up fairly routinely at about 10-20 pounds (once again I have two)

the brake pedal vacuum switch is the same for all variants and there is a precut hole for it to plug into and the plug from the loom is likewise just sitting there waiting for you.

the bellows sits on the inner apron just to the rear of your fuse box and this is a diesel only part. There are predrilled holes in your apron to take the bellows so it just bolts up. They are easily sourced from UK Ebay and expect to pay about 5-10 pounds I ended up with two because I just kept buying stuff I saw "just in case".

Now just when you thought it was easy:

connecting the bellows to the accelerator pedal!!!

In the UK they were using drive by wire (DBW) from 1996 on and so there are only a few years where they made 300tdi's with cruise operated by cable.
these cars had some significant differences from ours and here's where you'll need to find that inner mechanic (or engineer)

the plate that sits on the firewall and through which your steering and brakes travel is different on the cruise model 300 TDIs. It has an oval hole (I have photos here) through which the cruise cable from the bellows to the accelerator passes and a ledge on the outside that accepts and locates the cable outer. This would be an horrendous job to remove and replace and so I simply drilled out an appropriate hole (this is accessible, but just, with a standard electric drill and I drilled numerous small holes to make the oval then filed out the centre). For the ledge I simply made one from a right angle bend in a piece of 1/8th plate sheet steel and hit it with an electric welder, also in situ. Its not as bad as it sounds and it worked a treat.
So now you have a hole to connect through but you need a short version of your accelerator cable to take from the bellows to the pedal. This is a diesel only item that you'll find easily enough by asking UK ebayers who are wrecking discos if they have one. (once again I now have two!)

the pedal! ah yes the pedal. OPTION 1
well the pedal IS different (although I could find no appropriate part number) but it comes as a unit with the earlier mentioned plate. I actually purchased the entire plate from the UK ($$ postage due to size and weight) but there are other, better, choices. The accelerator pedal is held in place by a blind rivett that acts as the axle for the pedal. this is bushed and sleeved to give a friction free action. If you don't want to import the whole lot you will need some friendly pom (like the guys at green oval) to grind off one end of the blind rivett, release the pedal, and send the pedal plus its axle to you. Once it gets here you can re-assemble - in my case I drilled and tapped the rivett and replaced the blind rivett end with a washer and bolt. All this exchange is do-able in the car but you need the bits first.
OPTION 2
The new accelerator pedal has a small lever (about 2 inches long) welded to it with a fork for accepting the cruise cable. For any of you welders out there I'm sure it'd be a simple task to make your own pick up. Once again I have photos and if I can figure out how to load them I'll attach to this sorry tale.

Ok why the air bag note back there?

I understand that the rotary coupler for models with airbags is suitable for cruise but the one for the non airbag models is not. As mine has airbags thius was not a problem but someone with intimate disco knowledge should be able to tell us this.

Pros and cons

Pros

- It was fun to do it and not hard for a non mechanic to achieve
- I live in Perth and we have lots of flat roads here so cruise is actually useful
- It can be fitted without major dismantling if you're not a purist and willing to "fudge" the factory set up
- its actually cheap to do all up cost around $100-150 which is less than aftermarkets

cons

- the cruise is unhappy about changing speed which I put down to the resistance from the injection pump spring (try it its strong!) Maybe the cruise models had a different spring tension or maybe a differerent vacuum pump but I can't find this out.
- you'll have to scour ebay to source the non V8 bits you'll need
- if you do a real "factory retro fit" there's a lot of disassembly and reassembly to do.

sorry can't figure out how to add photos - if anyone can help let me know and I'll email the photos to them and they can load them.

If I've forgotten something just ask and if someone is interested in my "spare bits" once again just ask (I'll sell them for what I paid)

good luck, johnd

Johnd photos of Cruise control.
A big thank You to Green Oval and Dave for there help and attached is link to site of more photos and select index at bottom of page to go to main Green Oval Site.
Link To Site
http://www.project-green-oval.fotopic.net/c1562805.html

-Pedel changes


Inside view pedel fitted

Photo of imported parts Thanks Green Oval




Green Oval Bellows