Help - 300Tdi Disco Overheating Mystery

[Xtreme]

I was wondering if anyone out there in AULRO land could offer any suggestions for a couple of UK friends travelling around Australia. I just received the following email from them. I'm not sure exactly where they are at present (I've asked via email) but I think they are still heading up the Qld coast.

[quote] "I wonder if you could help us with some advice or info if you can. We set off in our Discovery 1997 2.5 Turbo diesel at the end of February.... We had an overheating problem, it wasnt seriously affecting our travels but I am cautious and didnt want to leave it until we were in the middle of nowhere for the problem to really blow up so I had it looked at.

Conditions:
When we had been driving under heavy load up a very steep hill with the revs high but speed low.

Symptoms:
The electronic (not cable) speedo would start to fluctate and then some 20 minutes later,
The round red transmission warning light would come on.
If we stopped and left the enginge running the light would go off and you could continue
If we stopped and switched off we couldnt re-start the engine for some 20 minutes to half an hour.

We took it to a garage and they rebuilt the tranmission and torque convertor. On the face of it this has got rid of the problem, however a couple of weeks ago when we drove up a very steep mountain the speedo started to flicker again, then on the way back down this steep hill one of the brakes started smoking.

We took it to a garage and they discovered that a couple of the brakes had been stuck on and all the pads were fried. A pity as we had had them done at Graeme Coopers only 9 months before. At the same time as the brakes (about June 07) they also did a radiator flush and replaced the hoses.

Yesterday after an extended period of driving under heavy load again the speedo started flickering. I am convinced that this is an early indicator of overheating (i dont think it was designed to be but I think that the heat interferes with its operation).

I stopped and checked the engine and the turbo air intake pipe from the top of the intercooler was very hot, during the earlier overheating this pipe had actually burned the sound deadening material on the underside of the bonnet.

I am concerned about taking the vehicle across the centre of Australia and want to get the root cause fixed (I think it might be the inter cooler or the radiator). Do you or anyone else in the club have any ideas or guidance please?

Kind regards Paul & Carol" [end quote]

I'm sure that any advice, ideas or guidance would be really appreciated.

[Scouse]

There's no mention of what the engine temperature gauge is doing.

With the first mention of the electrical gremlins & a hard to start engine, I thought of a poor engine/transmission earth.

I think getting an accurate temperature reading would be my first priority.

[Xtreme]

Thanks for the suggestions Scouse - I'll pass them on.

It appears from the answers to some of the following questions (raised via direct email) that the engine temperature gauge is behaving normally.

Other comments and questions raised and answers given (in blue):-
Sounds like the engine is overheating. All you can do is to start from the front and work your way backwards until the problem has found.

YES - 1 Is the A/C radiator electric fan operating when the engine is under load?

NOT SURE WILL INVESTIGATE - 2 Is the A/C condenser, Intercooler or radiator blocked?

YES - 3 Is the main engine fan viscus coupling operating when the radiator water temperature is above normal?

NOT THAT I CAN SEE OR HEAR - 4 Is the main fan belt slipping under load?

YES, BUT 100%? - 5 Is the main thermostat operating?

WILL INVESTIGATE - 6 Is the water pump impeller fully operational? This can only be checked by removing the pump and inspecting. I also purchased a new water pump for my Defender $120.00.

NO - 7 Is the radiator header cap leaking under load? Any sign of fluid leaking down the on the header tank?

HMMM, I HOPE SO! - 8 Last thing to consider. Is the engine head gasket in good condition.


Based on your comments it sounds as though the cooling fluid is overheating. I think the auto transmission is also water cooled. This would explain why the engine cannot be started until the transmission has cooled down.
Most of the above can be easily checked but may require the removal of the radiator / intercooler. The hot turbo pipe would indicate a blocked radiator / intercooler.

Paul and CArol have very limited internet access while travelling otherwise they would have posted this problem and questions directly.
They asked me to pass on their appreciation and thanks for all suggestions/help offered.

[81stubee]

Probably not very likely by the sounds of those symptoms, but friends of ours when going through the centre in their 3.9 Auto Disco had the transmission overheat light come on. Turned out to be a faulty sensor in the gearbox. Had to wait a week for it to turn up.

Sorry can't be more help.

Stu

[discomuzz]

My advice?

STOP NOW!

1. Solve the problem and move on.

or

2. Buy a camper-trailer, take 200 litres of water, three weeks supply of food, a GPS and a RFDS radio.

Mmmm, I wonder what I would do

Best of luck to them, and, if they're around my way, PM their details and they can drop in for a feed, etc.!

[mcrover]

Well it sounds more like a Trans temp issue which I would put down to :

a. Trans cooler not working effectively, remove the original and fit an after market cooler that would be more suited to the load it is copping.

b. Using the wrong ATF, as temps increase due to an increase in load you have to increase the quality of the fluid in the box.

c. Was the trans built for the specs of what they are using the Disco for as they dont say weather they are carrying 3 tonne of gear and towing a van up the snowy mountians for instance, no standard LR trans and converter will stand up to that punishment.

d. The extra load that the brakes were putting on would also add to trans fluid temp.


The speedo flickering is probably caused by something in the speed sensor that doesnt like heat as there still is a sensor on the transmission it is just fly by wire rather than a cable.

Edit : Smell the trans fluid to roughly work out if it is working beyond it's highest working temp, if it is a darker colour and smells like it is burnt it will be a trans temp problem.

[Blknight.aus]

Im backing MCrover especially if its been fighting dragging brakes as well as working hard under a load.

The engine overheating might just be cuased by the trans oil putting too much heat into its exchanger and effecting the heat dissipation from the engine which will also be working harder than normal.

with all the extra heat hanging around it doesnt take much of a stretch of the imagination to see the relay or solenoid on the starter sticking or the gearbox/engine earth back to the battery breaking down.

I cant remember if the trans temp warning light is tied to the nuetral/park start switch but if it was then that also accounts for the non starting after shutdown while hot (If I had to design an auto Id do it)

[Taz]

My 300Tdi speedo plays up (flickers) every week or so. It's done that for 4 years and I've never had any overheating problems. I dont know what the cause is so I'm not saying there is no link - it's just my experience.

[Xtreme]

Thanks everyone for all the suggestions to date.
I've just emailed them direct to Paul & Carol who I'm sure will appreciate your help.

I'll keep you posted regarding the outcome.