Range Rover 1988 Temperature Sender

I had the dreaded red-line temperature gauge problem that my 1988 RR
apparently suffers from, and duly panicked. Once I was calm, I
figured that it must be the thermostat, since the temp gauge was
red-line while the top-hose was cold. So I dropped the coolant, and
replaced the thermostat, and filled it all back up again. I took the
old thermostat into the kitchen, warmed it up like the proverbial frog
in a pan of water, and watched it open at precisely 192F. Drat.

Back out at the car I did the warm-up test, and sure enough it
red-lined before the engine was really warm. So I stuck the
thermometer in the top of the radiator where it comes back from the
engine before the thermostat opens, and measured 160 F. Clearly a bad
temperature sender, which I've ordered a replacement for.

Now, I'm lazy. I don't like dropping coolant, and the Haynes (book of
lies) says I don't have to to replace this sender. It does say I may
lose some coolant. The $64 question is of course, how much is 'some'.
Provided I depressurize and do it cold, can I get away with just
pulling the old sender out with a socket wrench and screwing the new
one in?

On a related topic, my RR is burning a lot of fuel, even though it's
running great. I'm getting about 8 miles/gallon, while just a couple
of months ago it was nearer 15. Rumor has it there's another
temperature sensor for the ECU which could be causing a problem like
this (ECU things engine cold, pumps in fuel), but I can't find any
ref. to it in Haynes, and don't know where to look on my engine.
Doesn't smell rich, but with a catalytic it wouldn't would it?

Any help would be greatly appreciated. Please post replies here, the
email address above is dead (too much spam).

Simon.

Well a partial reply to myself, in the hope others might find it
useful. This time laziness was good, and Haynes was right. My
procedure:

Depressurize the cooling system by removing the expansion tank cap
(then put it back on to create a vacuum useful in a moment). Have the
new sender handy with its aluminum O-ring already on it, take an 18mm
long-style socket and unscrew the existing sender until finger-tight,
then pull it all the way out. Lost about 2 tablespoons of coolant in
glug-glug mode before I was able to finger-tighten the new one in.
Finish up with the socket, tight but not not too tight. Stuff paper
towel down on top of the engine before you start if you care about
cleanliness 10 minutes from start to end. I think having the
expansion cap back on helped slow the loss of coolant, but it wasn't
spewing anyway.

The new sender works lovely, the gauge is exactly at 50% when the
thermostat opens. Now all I've got to do is figure out how to stop
her running obscenely rich until she gets warm: too many short trips
about town might be causing the excessive fuel usage, but that's what
we use her for: carting kids, dogs, groceries etc. I don't feel too
guilty though, she's went down the Grand Canyon and through rivers in
her younger days.

Simon.

[email protected] (TimeDilation) wrote in message news:<[email protected]>...
> I had the dreaded red-line temperature gauge problem that my 1988 RR
> apparently suffers from, and duly panicked. Once I was calm, I
> figured that it must be the thermostat, since the temp gauge was
> red-line while the top-hose was cold. So I dropped the coolant, and
> replaced the thermostat, and filled it all back up again. I took the
> old thermostat into the kitchen, warmed it up like the proverbial frog
> in a pan of water, and watched it open at precisely 192F. Drat.
>
> Back out at the car I did the warm-up test, and sure enough it
> red-lined before the engine was really warm. So I stuck the
> thermometer in the top of the radiator where it comes back from the
> engine before the thermostat opens, and measured 160 F. Clearly a bad
> temperature sender, which I've ordered a replacement for.
>
> Now, I'm lazy. I don't like dropping coolant, and the Haynes (book of
> lies) says I don't have to to replace this sender. It does say I may
> lose some coolant. The $64 question is of course, how much is 'some'.
> Provided I depressurize and do it cold, can I get away with just
> pulling the old sender out with a socket wrench and screwing the new
> one in?
>
> On a related topic, my RR is burning a lot of fuel, even though it's
> running great. I'm getting about 8 miles/gallon, while just a couple
> of months ago it was nearer 15. Rumor has it there's another
> temperature sensor for the ECU which could be causing a problem like
> this (ECU things engine cold, pumps in fuel), but I can't find any
> ref. to it in Haynes, and don't know where to look on my engine.
> Doesn't smell rich, but with a catalytic it wouldn't would it?
>
> Any help would be greatly appreciated. Please post replies here, the
> email address above is dead (too much spam).
>
> Simon.

Well a partial reply to myself, in the hope others might find it
useful. This time laziness was good, and Haynes was right. My
procedure:

Depressurize the cooling system by removing the expansion tank cap
(then put it back on to create a vacuum useful in a moment). Have the
new sender handy with its aluminum O-ring already on it, take an 18mm
long-style socket and unscrew the existing sender until finger-tight,
then pull it all the way out. Lost about 2 tablespoons of coolant in
glug-glug mode before I was able to finger-tighten the new one in.
Finish up with the socket, tight but not not too tight. Stuff paper
towel down on top of the engine before you start if you care about
cleanliness 10 minutes from start to end. I think having the
expansion cap back on helped slow the loss of coolant, but it wasn't
spewing anyway.

The new sender works lovely, the gauge is exactly at 50% when the
thermostat opens. Now all I've got to do is figure out how to stop
her running obscenely rich until she gets warm: too many short trips
about town might be causing the excessive fuel usage, but that's what
we use her for: carting kids, dogs, groceries etc. I don't feel too
guilty though, she's went down the Grand Canyon and through rivers in
her younger days.

Simon.

[email protected] (TimeDilation) wrote in message news:<[email protected]>...
> I had the dreaded red-line temperature gauge problem that my 1988 RR
> apparently suffers from, and duly panicked. Once I was calm, I
> figured that it must be the thermostat, since the temp gauge was
> red-line while the top-hose was cold. So I dropped the coolant, and
> replaced the thermostat, and filled it all back up again. I took the
> old thermostat into the kitchen, warmed it up like the proverbial frog
> in a pan of water, and watched it open at precisely 192F. Drat.
>
> Back out at the car I did the warm-up test, and sure enough it
> red-lined before the engine was really warm. So I stuck the
> thermometer in the top of the radiator where it comes back from the
> engine before the thermostat opens, and measured 160 F. Clearly a bad
> temperature sender, which I've ordered a replacement for.
>
> Now, I'm lazy. I don't like dropping coolant, and the Haynes (book of
> lies) says I don't have to to replace this sender. It does say I may
> lose some coolant. The $64 question is of course, how much is 'some'.
> Provided I depressurize and do it cold, can I get away with just
> pulling the old sender out with a socket wrench and screwing the new
> one in?
>
> On a related topic, my RR is burning a lot of fuel, even though it's
> running great. I'm getting about 8 miles/gallon, while just a couple
> of months ago it was nearer 15. Rumor has it there's another
> temperature sensor for the ECU which could be causing a problem like
> this (ECU things engine cold, pumps in fuel), but I can't find any
> ref. to it in Haynes, and don't know where to look on my engine.
> Doesn't smell rich, but with a catalytic it wouldn't would it?
>
> Any help would be greatly appreciated. Please post replies here, the
> email address above is dead (too much spam).
>
> Simon.