Pug 306 over-heating (or not)

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Tim Jenkins - 26 Jul 2006 15:07 GMT

Hi,

I have an 'S' Reg Pug 306 Meridian 1.4 - recently the engine temperature
gauge has started creeping up above 90 especially when the engine is under
load it creeps up into the red. The fans work OK and I can't see any leaks
etc.

Got home last night, left the engine running on the drive, temperature
dropped back down to normal 90 , noticed that whenever I put a piece of
electrical kit on, the temperature gauge climbed instantly - switch it off
then it dropped back again. With temperature at 90, I put the cold blower,
rear heater, hazard flashers and main beam on and sure enough - up jumps the
temperature needle into the red. Switch everything off....back to 90 again.

Any ideas ? Thinking its an Electrical problem, the Haynes manual wiring
diaggram shows an Engine Coolant sensor and an Enginer Coolant sender - any
ideas what the difference between the 2 is - I was going to replace one (or
both).

Cheers,
Tim

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Steve Birch - 26 Jul 2006 20:25 GMT

> Got home last night, left the engine running on the drive, temperature
> dropped back down to normal 90 , noticed that whenever I put a piece of
[quoted text clipped - 3 lines]
> the temperature needle into the red. Switch everything off....back to 90
> again.

<snip>

Tim,

I've heard of this before.
I'd suggest checking for an earthing problem in the first instance. Look for
corrosion of the wiring from the battery negative to the car chassis.
Replace it if necessary. This MUST be a really good solid connection or you
are asking for problems. Similarly, I seem to recall that there is another
wire that earths the engine itself to the car chassis.
If you have a poor earth connection like this, then when you turn on
something that consumes current from the battery, a small voltage appears at
the sensor wiring which can cause incorrect readings.

Hope this helps,

- Steve

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David Hearn - 26 Jul 2006 21:41 GMT

>> Got home last night, left the engine running on the drive, temperature
>> dropped back down to normal 90 , noticed that whenever I put a piece of
[quoted text clipped - 21 lines]
>
> - Steve

Negative earthing strap goes from battery to engine, and then from
engine to chassis. Standard wiring was to have both leads crimped into
a single connector on the engine. I had bonkers electrics problems one
time (generally not starting, sometimes starting and saying I was doing
140mph and then back to 0 in half a second whilst all number of relays
were clattering!). All traced to a broken earth strap. Lead from
battery to engine was fine (hence starter turned etc) - but strap from
engine to chassis was intermittent. When it made connection, ECU was
connected and it would start, any movement then made an intemittant
connection, causing dodgy readings etc. AA guy fixed it for < £5 (for a
new earth strap) and everything has been fine since.

D

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Tim Jenkins - 30 Jul 2006 21:21 GMT

> Tim,
>
[quoted text clipped - 11 lines]
>
> - Steve

Steve,

Bingo ! The earth strap had completely corroded from the engine to the
chassis - spot on with your diagnosis - much appreciated.

Will fit a new one tomorrow and fingers crossed it will fix the problem.

Cheers,Tim.

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