[xj] V12 coolant temp sensor

So, prompted by an earlier post, I am inquiring as to the
effects of a faulty coolant temp sensor.
So far, this is what I am seeing:

  1. When cold, engine will start readily but then after about
    5 seconds it will stall unless I gently touch the gas until
    the temp needle beings to move. Starting warm is no problem.

  2. Engine runs at about 80 C. Granted it is cold out, but
    even idling in my garage it doesn’t get higher than 80 or so.
    I had gotten used to this, as my fan clutch was frozen for a
    month so it ran cold. This is now fixed but the engine
    never gets up to 88 or higher.

  3. There is a shuddering at idle coming from the right bank

  • it more pronounced from the passenger’s seat. Could this
    be related?

I will be replacing the coolant temp sensor ASAP, what
should I use instead? Any brand? Temperature setting?
ANy tips?

Oh, remember back when I thought I had a blown valve train?
Well using a stethoscope I found out the clicking is coming
from the fuel injectors. They all click, and I think it is
louder than before. Am I imagining things?

Thanks,
Chris
1987 V12 VDP ‘‘Alice’’–
thetopdogg
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Chris,

I’ve found the coolant temp sender has a very dramatic effect on engine
running. I had disconnected mine when I was doing some work and forgot
to reconnect it. The engine started fine, and it drove well until about
60C on the gauge. At that point it would sputter and buck if I applied
any more than the gentlest touch to the throttle. It was enough to roll
along at 30 km/h but not much more. When I reconnected the wire to the
sensor the car ran normally.

Regarding your point 1: You shouldn’t have to keep your foot on the gas
to keep it running. That sounds like a stuck piston in the AAV. H&H
prestige in Australia has a rebuild kit for about $125 CDN landed here.
It was simple to do, and a new valve from you dealer is $600 CDN. It
only took a week for my kit to arrive by airmail. Do a web search and
they have a step by step procedure for rebuilding the valve.

Point 2: That sounds like a stuck thermostat. Mine did that, and I
changed them, and it ran at 88. The coolant temp sender has a major
effect on the fuelling, so if you are running cold it will enrich the
mixture. It won’t take long to change the thermostats, although the
right side is a pain. I paid just over $50 CDN for a pair of thermostats
and the upgraded gaskets from my dealer. The new gaskets are worth
getting, they are really nice to work with. Make sure you properly fill
the cooling system when you’re done, otherwise you’ll have the stumbling
that I talked about first. Raise the front of the car on axle stands,
fill the system at the filler neck in front of the AC compressor and
run until the thermostats open. Top it up as necessary. Full, the
coolant level should be about 3" below the neck. Also have a look at the
overflow bottle on the LH inner fender. There should be some coolant in
there, but not much. Don’t fill through this cap.

Point 3: Are all the injectors clicking on the RH side? It could be a
loose wire to an injector. Just hold a long screwdriver to the injector
and the other end to your ear and you should be able to hear each
injector click. Also check that the plug wires are firmly attached to
the cap and to the plug. I’ve had a plug wire pop off the cap, but still
be held by the rubber boot so it looks ok. The wires are so stuffed in
there that they can sometimes come off the cap.

It sounds like your coolant temp sensor is fine, check the other things
first.

Craig
92 VDP V12

thetopdogg wrote:>So, prompted by an earlier post, I am inquiring as to the

effects of a faulty coolant temp sensor.
So far, this is what I am seeing:

  1. When cold, engine will start readily but then after about
    5 seconds it will stall unless I gently touch the gas until
    the temp needle beings to move. Starting warm is no problem.

  2. Engine runs at about 80 C. Granted it is cold out, but
    even idling in my garage it doesn’t get higher than 80 or so.
    I had gotten used to this, as my fan clutch was frozen for a
    month so it ran cold. This is now fixed but the engine
    never gets up to 88 or higher.

  3. There is a shuddering at idle coming from the right bank

  • it more pronounced from the passenger’s seat. Could this
    be related?

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: http://www.jag-lovers.org/lists/search.html

To remove yourself from this list, go to http://www.jag-lovers.org/cgi-bin/majordomo.

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