AU II Wagon Overheating

badoc · 13-12-2012, 07:05 PM

Hi guys,

I'm hoping someone may be able to give some advice on my AUII Wagon that is starting to overheat when stopped (traffic lights, etc).

I'll outline the problem and what I've done to to try to fix it so far after reading the forums.

Problem: After warming up to a normal temp (driving), the car will start to overheat at any time it is stopped at lights or in traffic. It has reached the red (with the corresponding engine light) a couple times. The guage will go from between the 'N/O' to red if stopped within a few minutes.

What I've done so far:
When it happens, I turn the heater on high and it will either prevent the temperature from rising further or help it to come down slightly.

I've ensured there are no leaks from the system, replaced the thermostat and given the system a treat and flush. A bit of brown crap came out, but after the flush it is all clear water. I put in new coolant.
I checked the fans with the air-con on at startup and they work. It will run for 15-20 minutes (I haven't left it any longer, because it happens much faster on the road) like this and the fans are still on. I checked the drive belt and it's running the water pump. The radiator was only replaced about 2 years ago by a previous owner.

However, when I checked the car today (pulled over while driving) twice the fans were not running when the guage was in the red.

Is it possible the fans are turning off on the road?

What else could be causing this problem?

Thanks guys, much appreciated.

Spirit · 13-12-2012, 08:07 PM

I'd say the thermos need replacing. Check the fan relays as well but fans most likely in my opinion. Had similar problem, replaced both thermos and all good.

Maka · 13-12-2012, 08:21 PM

G'day badoc, welcome to AFF! Check fuses 9 & 10, relays 6, 7 & 13 in the power distribution box under the bonnet. Fans come on when you hit the a/c button when cold? I'de still check the fans are operating correctly once the fuses & relays are ruled out. The sensor on the back of the cylinder head shouldnt be overlooked also.

cheers, Maka

SportsmanV8 · 13-12-2012, 08:24 PM

Hi mate,

Are you certain it's not low on water? I ony ask because my AU used to lose water (from a leaking radiator), but never left a puddle.

Otherwise it may well be the thermos or some electrical thingamabob that tell them when to work..

Sorry, maybe not a lot of help but maybe useful to you

4ford · 13-12-2012, 09:27 PM

Replace the radiator cap, with the correct one, be very sure of that!

Just because the fans run with aircon selected, doesn't mean they will run when an o'heat is sensed! (I think you've already proved that!)

The fans need two things to run, (1) power - check both the relevant fuse and power relay, and (2) something to trigger their startup at the right time - find out what that is (probably the sensor in the rear of the c/head) and replace that!
If the fans run with aircon, and don't run with an o'heat sensed, I'm thinking that the o'heat sensor is not triggering the startup! (#2 above)

I've heard lots of stories about the incorrect radiator cap being fitted and causing lots of cooling system problems.

Get the cooling system pressure tested!

GK · 13-12-2012, 09:29 PM

Quote:

Originally Posted by Maka

G'day badoc, welcome to AFF! Check fuses 9 & 10, relays 6, 7 & 13 in the power distribution box under the bonnet. Fans come on when you hit the a/c button when cold? I'de still check the fans are operating correctly once the fuses & relays are ruled out. The sensor on the back of the cylinder head shouldnt be overlooked also.

cheers, Maka

This is a good idea from Maka and too easy to test.

Turn on the car, turn on the A/C and if the thermos don't come on, then you know to check the fuses, relays and then if they're good, it could be time for new thermos.

All the best with it.

GK

badoc · 14-12-2012, 12:19 AM

Thanks for the assistance, gents, much appreciated. I'll update you all once I've had a chance to follow up on some of this advice.

badoc · 15-12-2012, 06:50 PM

Hi all, I checked the fuses and relays and they are all good. So now it's either the sensor or the thermos. Any tips on how to get to the sensor? I dot have the biggest hands in the world but tried today and there wasn't much room between the c/ head and firewall to be able I access it. (Am I going for the right one?)

Cheers all

Maka · 15-12-2012, 07:54 PM

G'day badoc,

yep thats the one, but wait! Here's some reading material BEFORE ripping out the cts (cylinder head temp sensor) -

http://www.fordforums.com.au/showthread.php?p=3060044

http://www.fordmods.com/ford-4l-and-...e-t109679.html

I would check the operation of the fans first (direct 12v to them individually like in the links above), then the sensor, hopefully the problem lies in one of those two. Keep us posted!

cheers, Maka

AUFanboy · 15-12-2012, 08:02 PM

Hey,

The sensor is connected to the ECU, which then sends the temperature info (along with other stuff) to the dash cluster via a serial data connection. So if your temp gauge is working then the sensor must be working. The fans should come on low speed when the gauge reaches the last mark before the N (of Normal). They should then switch into high speed mode (jet taking off) at about 105 degrees, which on an AUII will be just between N and O (the gauge is faked somewhat and sits in the same spot from 92 to 110ish). I would replace all three relays and start the car and check for low and high speed fan operation.

Here's the schematic from the manual:
http://www.fordwrm.co.za/manuals/For...on_auII664.pdf
and
http://www.fordwrm.co.za/manuals/For...on_auII665.pdf

badoc · 16-12-2012, 02:12 PM

Hi guys,

Thanks for the extra bits of advice Maka and AUFanboy. For sure the temp gauge on the cluster is working - so I guess that rules out the CTS.

I've now tested the fans with direct 12V. Both primary and secondary run normally.

So, before I change the respective relays and assume it's done an dusted with the help of you lads - just one more question to draw on any other experiences you all may have had.

Is it still possible its the thermos, even though they run fine on direct 12v and run on startup with the aircon?

Cheers,

Maka · 16-12-2012, 04:11 PM

Hey badoc,

i believe the fans should be good - you could throw new relays in & it still wont work- a crook ecu, wiring loom damage & bad earth points are other items that can be the culprit.

How did you check the existing relays? Did you swap the horn or headlight relays around with the thermo fan relays? Can you confirm theres no coolant level sensor in the coolant header tank? Series 2 AU Falcons apparently do not have them.

I reckon (i may be wrong) the ect can be still faulty & read temp correct but wont send temp info to ecu, so either the ecu is not getting the temp info (ect or wiring loom etc) or the relays/ecu or wiring loom ect is damaged and not sending the activate signal to the thermo's. Bush mechanic rule no 1- go cheaper fix first!

An ecu scan could come in handy down the track if having no luck (best to do right at the start of troublesooting though )

cheers, Maka

badoc · 17-01-2013, 02:30 AM

Hey guys,

Sorry for the big delay in replying - Xmas and all has kept me away.

After a couple hours of deeper investigation, I found a bit of a weird petina had formed on one of the clip/connectors from the looms to one of the fan relays. Bit of a scrape with a flat head screwdriver and it solved the problem.

Thanks so much for all the tips and advice. Saved me from buying a new fan for no reason!

GK · 17-01-2013, 05:06 PM

Quote:

Originally Posted by badoc

Hey guys,

Sorry for the big delay in replying - Xmas and all has kept me away.

After a couple hours of deeper investigation, I found a bit of a weird petina had formed on one of the clip/connectors from the looms to one of the fan relays. Bit of a scrape with a flat head screwdriver and it solved the problem.

Thanks so much for all the tips and advice. Saved me from buying a new fan for no reason!

So glad that it was something simple AND inexpensive. Sadly, often that is not the case.

Another win for the AUvians! Well done guys!

GK