Strange problem - any ideas?

**Frenchie** · 14th March 2006, 12:04 PM

Hi All,

have just returned from a lovely two weeks in Coral Bay, al good apart from an irritating and somewhat worrying problem with the Defender.

On the way up the temperatier guage started doing trange things. It would suddenly shoot from 'normal' (just below half way), right to the top of the guage, then back to normal again, within a second or so. This was accompanied by a momentary loss of power, which I interpreted as the ECU responding to the sudden aparent rise in temp.

It continued to do this on a random basis for the rest of the trip, sometimes not flicking all the way to the top, sometimes only every 10-20 km but occasionally several times in a row.

I did stop and check for signs of overheating but it everything seemed to be fine.

I initially thought that it must be an electrical problem, perhaps a faulty sender. Rovertech (thanks Kevin) sent me a new one but that didn't help. Other strange thing was that it only did it with the camper trailer attached. Had a day trip to Exmouth, 150km each way at 120kmh, didn't happen once. Did some 4wding, no problems. Driving around Perth when we got back, no problems.

I tried disconnecting the trailer wiring, tried turning off other stuff like the aircon, Engel etc, no change.

The only other thing is that the back end was sitting lower with the trailer attached, and the vehicle was working harder. On the way back it also seemed more frequent on steep (for WA) hills, so this brings me back to the cooling system.

I had the vehicle serviced before we left and asked for the cooling system to be checked thoroughly. It was pressure tested and given the thumbs up, but I was wondering if perhaps there was some air in there? I tried bleeding it as best I could and did manage to get a fair amount of air out.

Any ideas?? :?

jessie_xa · 14th March 2006, 12:38 PM

Hi Frenchie,
Just over in Perth the other week, boy had it changed since the last time I was there (come to think its not the same since I left).
Any way, the temp gauge sender and ecu sender are not on the same loom (circuit), so the high temp plus the cut in power could just the problem, not the ecu been the problem from the high temp reading.

As its sounds like a electrical problem have a look at the wiring throughout the engine bay for any shorting, if there is none work back to the ecu and the dash. Dont look just for bare wires but shorting between wires and or connectors as well. Plus from the batter.
The temp gauge works on resistance with a bio strip, the hoter it is the more volts flows (correct me if Im wrong guys) laymans terms full 12volts gauge should read im so hot im outa here (if you short it the block you
get full hot reading).

tombraider · 14th March 2006, 12:50 PM

This is the *exact* manner that the engine responds to overheating.

Your radiator is either blocked externally with mud etc or your viscouos fan is not operating correctly. (Or both) Theres a lot of fin area to block between the intercooler / AirCon & Radiator and this will have all sorts of crap in there reducing cooling.

The guage rises rapidly and then the engine goes into preservation mode, cutting fuel and feeding air only through the cylinders (hence the power drop) this rapidly cools the cylinders and the engine resumes.

Continual driving after the first instance will induce this cycle over and over.

Another give away is continual operation of the viscous (locked up and whirring away) even at lower speeds.

I had my radiator cleaned 5 times using high pressure cleaners yet it took being physically removed and cleaned to remove all the blockage.

It was amazing how much junk still came out even then.

Since then the defender has ran like a dream.

Cheers
Mike[/b]

**Frenchie** · 14th March 2006, 03:51 PM

Originally posted by tombraider
This is the *exact* manner that the engine responds to overheating.

Your radiator is either blocked externally with mud etc or your viscouos fan is not operating correctly.
Cheers
Mike[/b]

This could be so, as I have been in the mud a few times over winter, however would that account for such rapid (under a second) fluctuations from normal to off the guage then back again?

tombraider · 14th March 2006, 04:59 PM

The guage is not linear nor progressive in its nature (unfortunately) to allow for normal cycling (up/down hill etc) the guages have a (for lack of better word) "Sweet spot" where everything inside this range displays normal.

Exceed this range and up she goes!

Sorry!

Cheers
Mike

**disco_ute** · 14th March 2006, 05:25 PM

I had almost the same problem with my td5 disco last week.... I also thought it was a faulty sensor however after having the problem checked out by a professional it was the wiring loom from the air box just near the turbo (near the hook that is used to remove the engine) LR had feed the original wiring loom thru the hook and the wires and shielding had just rubbed thru over time and earthed against the engine this caused the erratic faults in my case... HTH

Mick

**George130** · 14th March 2006, 06:15 PM

That was exactly what mine was doing. I did have the signs of heat though. Mine was caused by a combination of
1 Worn water pump. Would leak under load
2 Leak in pipe
3 Jammed Thermostat traping air bubbles
4 Leaking exhaust manifold causing ECU to dump extra fuel in to stop the lean-out readings.

**Frenchie** · 14th March 2006, 06:31 PM

Hmm, sounds like a visit to the doctor is in order! :?

**camel_landy** · 14th March 2006, 07:23 PM

Ah ha!

Sounds like an earth problem... Easily solved by running an earth strap from the -ve on the battery to the engine block.

The problem with the Defender is that LandRover assume that if they attach an earth strap to the transfer case, they'll get electrical continuity to the front of the engine. For some reason, if the engine loses this, one of the symptoms is the temp gauge shooting up... I've seen it on several vehicles, including my own!

To solve it on mine, I just ran an earth strap direct from the battery and attached it to one of the bolts on the starter motor.

HTH

Mark.

tombraider · 14th March 2006, 07:45 PM

Nope not this time.. This is overheating (minor) but enough to trip the ECU.

Easiest test is that the Viscous Fan is running more often than usual. It is heat activated

so if its running more often theres more heat to discipate being generated.

The key point in the initial post was "only happened when the camper was on" leading to extra load generating heat....

I'm betting good money its the radiator blocked externally.

Cheers
Mike

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