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keltik's 1986 Jag XJ40


keltik

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Being a jag owner, i'd say a lot of that candy will be in his pockets. And that he may be located out side a primary school somewhere.

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Got through a bit. Then added a can of Lynx Africa and a 6pack of Monteiths to it and turned up at the gfs house. Results were good.

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Alright so one problem thats been bothering me is the "LAMP FAILURE" warning on the dash whenever the lights are on. The XJ40 employs a rather overcomplicated approach to lighting.

The light switch and indicator stalks are all connected to the lighting ECU. When you command a light to turn on, the lighting ECU sends a signal to all 4 of the lamp modules (one for each corner) which contains the relays for each light set. Every lamp gets its own relay.

A 2nd circuit inside these lamp modules provides feedback to the instrument cluster module as to whether or not the lighting command has worked. If a bulb has blown or a relay is nakkered - it drops the fault signal line to ground and the dashboard display shows a big picture of a blown bulb with a red flashing outline and "LAMP FAILURE" appears in the trip computer display. Reeeeeally rather annoying at night.

First I tried cleaning the grounds up, no luck. 2nd stop was to crack into the 2 'new' lamp modules which i installed to suit the new headlights. Quite simply made - it was easy to rip them apart and scan through each one looking for problems. It didnt take long to find a few dry solder joints in the monitoring circuit board.

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Corrected that and bingo - everything is working as it should.

Next mission is to sort out the coolant level sensor which throws up "LOW COOLANT LEVEL" messages on the same bright screen. It fucks me off far less frequently tho so its not as big a priority. The float switch doesnt float as well as it used to, so when the coolant gets hot - it sinks and trips the warning. I think i'll just stick some low density foam to it instead of paying 30 quid for a new one.

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Piece of cake to bypass but i like to keep as much original gear working as possible. I mainly do it because its more fun to try and fix things than remove them.

For some reason i do appreciate authenticity more with this car.

lush.

that's what i'm talking about. fixing the wizardy rather than just simplifying everything :D. mucho respect

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Nah the coolant disco lights really was a dodgy sensor. All from Taupo to Rotorua the "LOW COOLANT OMG" light was on in my face and i did a pretty good job of tuning it out.

Then after leaving the pub i noticed the temp gauge 2 notches above where it normally sits, so about 100*. Pulled over to check and managed to dump about 5 liters of water into it....only to see it pissing out of the pump weep hole.

Right now im off to Repco. Dont fancy my chances tbh but they did have a thermostat in stock for it. Worst case scenario I'll buy one out of the UK for 100GBP.

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  • 2 weeks later...

Progress! Got the water pump off tonight. Jag forums reckoned it was a 2 hour job to replace, after 20 minutes i was ready to put the new one on. Although i dont have a smog pump in the way or a rustfucked engine bay.

So the water pump spins freely but is nice and smooth and has good resistance in it. With a flick of the wrist it will spin about 3-4 turns and stop. The weep holes both look clean and theres not much crud inside the pump housing at all. So i reckon its a relatively new pump.

The gasket on the other hand was some flimsy cornflakes packet stuff. I cant be 100% sure since it may have gotten damaged when i removed the pump - but the gasket had a damaged section on it near the bottom in the same vicinity as one of the bolts that was nowhere near as tight as the others.

At this point im reluctant to order a new pump from the UK for ~$210. I dont really want to get a rebuilt one either when for thirty more i can have a genuine new one.

Viscous fan clutch feels shagged tho. Spinning it upright by hand, it turns 3/4 of a turn smoothly then makes a scraping noise/feel for the last 1/4. Never played with one before so that could be normal?

Thinking about sourcing a new clutch, seems to be a generic size. Making a new gasket and slamming it all back together and trying my luck. It wasnt exactly hard to take apart so might be a good idea?

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Any viscous fan problem would not cause this -

to see it pissing out of the pump weep hole.
However a damaged gasket would show that symptom - chuck a new gasket on, tighten all hose clamps within a hands breadth of the pump and pressure test..

I wouldn't worry about the viscous till you fix any leaks...

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