Overheating

1falconer1 · 03-01-2009, 03:38 PM

I have a 1999 AU with 177k on the clock. Noticed recently that she was starting to overheat when towing a 1400kg caravan. After a few attempts with the local garage fixits came to naught, I found that the fans weren't coming on. OK, I thought maybe a fuse or relay. Local auto elec couldn't trace it but thought that the temp. sensor on the head might be on the blink - but he didn't know where it was! A good buddy rigged up a temporary fix where the fan is turned on when the ignition is turned on - a cool engine! However, I then realised that while the temp. gauge on the dash doesn't show any drop, the engine seems a lot cooler under the bonnet now than it ever has! Maybe the engine has been running hot for a long while and hasn't showed on the dash temp. gauge?
Q - where under the bonnet is the sensor for the switch to turn the fan on?
Q - is it possible that the temp. gauge on the dash isn't part of the setup to the switch that operates the fan and is therefore not a good indicator of temperature?
Q - the boiling is only a recent ocurrence, but the under-bonnet high temperature has been evident for a long time. Could there be a radiator blockage that effectively blocks off say 1/2 the radiator which leaves the temperature OK for general use with the fan operating, but towing a caravan becomes too much? (with or without the fan)

I'm 2 hours from a Ford dealer who charges $100 an hour. I'd like to be able to point a local guy at $45 an hour in the right direction if I can.

Any ideas anyone?

bodes-sh · 03-01-2009, 04:59 PM

the cylinder head temp sensor is in the rear of the head. you can see if above where the exhaust manifold runs and around to the back of the head. as for that and the temperature gauge, that sends the signal to the ecu which controls the gauge on the dash and the thermofans aswell. there is a diagnostic mode you can put the car into to see what temperature the ecu is seeing, it shows in the digital display on the dash. i will have a look for it, but someone else may be able to post up the details of it.

try this and see what temperature it tells you the coolant is http://www.fordmods.com/forums/Instr...stics-d34.html

**Mechan1k** · 04-01-2009, 01:32 AM

I had so many issues with overheating over time in my AU ute ... I replaced everything that related to the cooling system ... and underload in Summer ... it'd still do it.

Even after installed a twin core ADRAD radiator.

In the end I traded the ute in for a newer one.

I dod a mod to my relays for the thermo fans ... as there are 3 relays that run the high and low speed for these fans ... what I had rigged up was when i turned the A/C on Fan speed 1 ... the thermos would switch immediately to high speed and stay like that as long as the A/C compressor was on.

I ran the diagnostics on mine as well ... and when it overheated ... it only did it at the back of the head (tested on a dyno with the laser pointer thermometer) ... we couldn't figure out why it was doing it ... the rest of the cooling system was running around 94 deg C ... the back of the head at the sensor would spike to 118deg C (that's when the gauge would be at hot and the red warning light comes on ... WAY TOO LATE really.)

The Cydlinder head temp sensor only tells you the temp of the head ... not the coolant ... as it is screwed into the alloy head ... and not into any of the galleries.

Apart from thermo fans I do have on suggestion ... replace the water pump (even if it is not leaking) .... I found the internal vanes in mine had corroded away ... but wasn't leaking ... and it's efficiency was poor at best.

Also get your radiator flushed and pressure tested just to be on the safe side .... is it the original radiator?????

1falconer1 · 06-01-2009, 09:28 AM

Finally found a local guy with a scanner who knew how to use it.
Problem solved! The fault was in the relays under the bonnet. Apparently the part of the relay set-up you can see is separate from all the underlying wiring and connections and the whole thing was only held together by the relays themselves when they were plugged in and some had become detached from the base. Unplugged all relays, CRC'd the relays & their female parts and replaced the relays gently. Magic! This also fixed the problem I had on here ages ago where the ABS warning light was on. Double Magic!
All fans now operating at correct temperatures, Air con fan on, no overheating and ABS warning light off too!

skidmark75 · 13-11-2009, 08:16 AM

Hi I'm a newbie here. Have an AUII ute, has been displaying symptoms similar to what you described. I have found localised overheating at the rear of my cylinder head too. Any clues as to what causes this in particular? I'm thinking either blockage in a passage in that location, or water pump old and ineffecient.

GK · 13-11-2009, 05:04 PM

Quote:

Originally Posted by 1falconer1

Finally found a local guy with a scanner who knew how to use it.
Problem solved! The fault was in the relays under the bonnet. Apparently the part of the relay set-up you can see is separate from all the underlying wiring and connections and the whole thing was only held together by the relays themselves when they were plugged in and some had become detached from the base. Unplugged all relays, CRC'd the relays & their female parts and replaced the relays gently. Magic! This also fixed the problem I had on here ages ago where the ABS warning light was on. Double Magic!
All fans now operating at correct temperatures, Air con fan on, no overheating and ABS warning light off too!

How the heck did the auto electrician miss that? You'd reckon an auto-elec would have had that sussed really quickly.

Glad you got it sorted, nice and cheaply too. Good job!

GK