Thread: OEM cruise into a 300TDI disco

G'day Johnd

You know what, I've just added another want to do to my list. Thanks for this , I'm sure my wife will be very pleased .

I have a 98 300tdi auto discovery and no cruise control and have thought occasionally about how hard would it be to retrofit cruise control to it.

What exactly is needed to get the oem cruise working?

I assume there is some sort of vacuum pump, throttle control and switches for the steering wheel or dash? What else is required and where do all the bits and pieces go??

Many thanks

Goldey

all comments for TDI auto disco 1995-1998 (I'm not sure about others)

1. vacuum pump - lives under the tray that houses your jack etc on lhs front just behind headlight. Bolt holes provided in the tray but you'll need three 6mm bolts and nuts. The wiring plug comes off the loom that also goes to your power steering sensor (low down below the radiator near where the lower hose goes in). This shares the part number with the V8s so should be easy for you to source. Vacuum hose goes from the pump (via a t-piece to the brake switch) to the actuator.
2. actuator (or bellows) lives up on the rhs inner guard apron near your fuse box. Unit bolts up to pre-existing nuts on the apron. I understand that this is also identical to the V8s (but they have it in a different place). A short cable leaves here to go to your accelerator pedal (or injector pump if you prefer - this is the fiddle). I think the short cable is TDI only and was on UK cars only (??) and so you might have to fit up a TDI accelerator cable to the injector pump to do the job.
3. steering wheel switch air bag model - you'll need to provide a slot in the soft rubber steering wheel boss to pass the switch through. make sure you buy a switch with the plug attached as it then plugs directly into the housing under your horn/airbag. Non air bag models you'll need a new steering wheel with the buttons on it (off a V8 is ok)
4. dash switch is the same for all models and the wiring plug is there but (on mine) extremely hard to find as its taped way back up behind your heater controls and your neighbours children will learn some new words as you try to reach it. Once you have it its a straight plug in.
5. brake vent switch - same as on V8s and clips directly into the pedal box frame and the connecting electrical plug is sitting there just waiting for you (tiny plug with two pink wires). Picks up the vacuum line from the Tpiece from the vacuum pump.
6. cruise relay- lives behind the kick panel on the drivers side below the dash and was already there on mine - maybe they all come with it fitted? but should be just a simple relay if you have to buy it.
7. cruise computer - apparently is the same as V8s and lives behind your glove box. Take the glove box lid off (easy) and you'll find the plug waiting there for you and the space on the electrical scaffold to bolt it (easy)

speed pick up is electronic via your gearbox speed sensor and you don't need to do anything here (at least I didn't) - its already wired in.

sorry to be so long winded but i hope all this helps

johnd

Different part number between V8 and TDi cruise control computers.

Where did you sorce all your bits and pieces?

Were they all Oz delivered as I was led to believe that 300Tdi wasnt available in Oz with OME cruise but that was from someone whom has been wrong before so I wouldnt be surprised if thats not the entire truth.

Hi McRover,
All 300Tdi's delivered into Australia did NOT come with cruise control.
Johnd is fitting cruise control to his with parts possibly from both the V8 & 300Tdi models.
In England all the 300Tdis used a drive by wire system, nearly the same as whats used in the TD5. There was no connection between the injector pump & throttle pedal, it was all done via an ECU.
I tried to price up a system for mine many years ago & wasnt worth the expense at nearly $2000k for all the components from UK.

If Johnd has ended up using both derivatives then all the best & what a great find, pity i didnt think of this years ago

Cheers

Originally Posted by sniegy

Hi McRover,
All 300Tdi's delivered into Australia did NOT come with cruise control.
Johnd is fitting cruise control to his with parts possibly from both the V8 & 300Tdi models.
In England all the 300Tdis used a drive by wire system, nearly the same as whats used in the TD5. There was no connection between the injector pump & throttle pedal, it was all done via an ECU.
I tried to price up a system for mine many years ago & wasnt worth the expense at nearly $2000k for all the components from UK.

If Johnd has ended up using both derivatives then all the best & what a great find, pity i didnt think of this years ago

Cheers

Ive looked a several systems from the elcheapo's from autobarn which then need several other componants to make them work due to the vacuum issue with diesels (way too much) so they need to be electronically controled which then is slow to react.

All the way to the VDO system at $600 so I would love to know how much all this cost as I would love to have it for the long hauls.

I generally dont like it but when we went to Alice Springs I found that is would have been worth it.

Have a look at NZ for cruise control parts as a few of the Jap imports are starting to be wrecked. I believe all Japanese spec Discoverys had cc. TradeMe ? New Zealand online auctions and classifieds. Browse, buy and sell online on trademe.co.nz would be a good start

What a great write up. I am just assembling all the bits to do the same on my 97. A photo of the actuator and the way it connects to the pump would be really useful.