Disco 1 overheating - help needed

[The Bullfrog]

have just bought a 94 discovery 3.9 v8 auto with eaton supercharger.:twisted:

Is overheating :( when under load and can't work out problem, please help. Have looked through countless posts on this forum and others and i don't seem to have the same problem... all others i have read had some other tell tale sign, whereas this is just overheating, with no other symptoms!!

Heater works great though :D

Have replaced radiator, viscous unit and fan, all new coolant and pressure flushed engine, checked water pump which looks brand new (think last owner having problems also as all plastic under bonnet is very brittle from heat), checked hoses, replaced thermostat and checked new one to ensure working and tried it without thermo stat, pressure flushed entire system.

no oil in water or vice versa, no water loss, no leakage, no steam from exhaust, just nothing!!!!! air con condensor clear and electric fans also working.

will cruise in cooler weather not a problem but as soon as too much load is placed on engine, it will boil it in no time flat!! once it is hot, even idling will not send it back down and engine has to be shut down. recent weather north of Geraldton, W.A. reacherd about 30 degrees (hottest days since ownership) and that was enough to overheat it with just normal driving!!

IF ANYONE CAN PLEASE GIVE SOME OTHER SUGGESTIONS???? even if it is confirming i need a new engine as i will look for a larger capacity (4.6 or bigger) to replace this one and do away with the blower!!

Also, if someone could advise if any of teh discoveries had a heater hose switch under bonnet on the driver side rocker cover??? this has one and it doesn't look factory... not sure if thsi could be a cause?? doesn't seem to be a switch for heater without it as coolant flows freely through lines without turning heater on..

[Ace]

Is it using any coolant? during general driving? Any water in the engine oil?

If its not using any water and just gets hot when under load i would say the radiator needs rodding. In the disco radiators the veins in radiator run horizontal so you dont flush the all the crap out with a general coolant change. The radiator needs to come out, take the tanks off the end of it and use rods to push the crap out of each channel in the radiator. Sounds like this might be your problem, especially if it runs fine when not under load but heats up quick when you give it some. It sounds like the radiator cant get rid of the heat quick enough when lots is produced. Has it got the original fan or has someone added thermo fans or anything like that?

[It'sNotWorthComplaining!]

Maybe you have an airblock somewhere in the engine that is causing a hotspot?

[PhilipA]

have just bought a 94 discovery 3.9 v8 auto with eaton supercharger.
Have replaced radiator, viscous unit and fan, all new coolant and pressure flushed engine, checked water pump which looks brand new (think last owner having problems also as all plastic under bonnet is very brittle from heat), checked hoses, replaced thermostat and checked new one to ensure working and tried it without thermo stat, pressure flushed entire system.



Did you replace the radiator with a NEW one? This certainly sounds like a blocked radiator so I would revisit .

Although seeing it has an Eaton Supercharger-
I wonder if the ECU is pulling out so much advance when the supercharger goes on boost that the amount of retard is causing overheating.

What sort of ECU is the car running?
Is it a MAP sensor type?
Does it now have an electronic advance control?

It is almost impossible to diagnose something like this from a distance without knowing how mods were done to the car.

I suggest you contact the fitters of the supercharger.
Regards Philip A

[Vern]

This sounds EXACLTY what my old 6.5 chev deisel was doing, would cruise ok but under any load would get hot, i ran a new patrol 4 core radiater which is alot bigger and it was still doing it.
Fixed it with a 80mm thick 2 core aluminium radiater, didn't get above 90c:)
then i stripped and sold it:(
Radiater just wasn't big enough, or wouldn't flow enough

[whyatts]

Check exhaust temperature as the supercharger could be causing the combustion temperature to be too excessive for a standard cooling system
Air fuel ratio should be checked, possibly running too lean under load.

[mike 90 RR]

IF ANYONE CAN PLEASE GIVE SOME OTHER SUGGESTIONS????

^^^^ Go visit the "Poster" above me ^^^^^^^


And seeing someone with a Dyno wouldn't go astray


In the meantime .... stop driving it till you get it sorted , otherwise you WILL be up for a new motor


Mike

[GuyG]

Also check to make sure that the air is actually going through the radiator, air will take the easiest route and if it can go around and not through the radiator it will

My fathers rangie was doing similar this to what yours sounds like its doing, we blocked the gaps and so far it seems to have improved it drastically.

[Ace]

Also check to make sure that the air is actually going through the radiator, air will take the easiest route and if it can go around and not through the radiator it will

My fathers rangie was doing similar this to what yours sounds like its doing, we blocked the gaps and so far it seems to have improved it drastically.

Making sure you haave a decent radiator cowling will make a world of difference to this aswell.

[The Bullfrog]

Had a sniff test done on coolant yesterday, no problems there, which was a good thing and a bad thing at the same time as i still don't know the problem, confirming it needs a new engine would have at least given me an answer!!

Radiator is brand new, so is not the problem, unless too small, but problem seems to be getting worse now as i can't cruise more than 5 kms without it overheating so is back in shed in pieces for the third time!!

However, the person doing sniff test suggested it could be the torque convertor as he had heard of nissan's having a problem similar to this when a bearing in torque convertor went. it would get red hot, overheat oil which would heat transfer into radiator and cook engine.

This could explain why it is getting worse maybe?? going to bypass the radiator part of transmission cooler and see if that makes a difference.

Next i will be pulling the vacuum off the supercharger so that is bypassed to see if that is causing the problems if auto comes up good.

As for supercharger fitment and mods, unfortunately i don't know who fitted it and exactly what they have done (think it may have been Jordan Rovertech, however was back around 1998 sometime i think, and they didn;t have any records and no longer fit them apparently). is still running vacuum advance on dizzy, ECU still standard one though don't know if they have re programmed it at all, eeverything else looks standard except all the extra vacuum lines and extended breathers running around the place.

Will see what i come up with today, have just borrowed an infra red thermometer so will check out temps of radiator, engine, trans etc to see how they differentiate.

Thanks for the replies

[Tank]

First thing I would check is the Vacuum Advance unit on the dissy, suck on the vacuum hose and see if the diagphram is working and not holed, if it's OK I would get some one experienced in setting up your dissy for supercharging. Disconnect the supercharger drive and see if there is a change in engine temp., does the supercharger have an intercooler, is it functioning properly, do you have a working thermostat fitted?, Regards Frank.

[The Bullfrog]

1. bypassed the transmission cooler in radiator and eliminated the auto being the problem, still started to overheat and auto remained cool.

2. Advanced the timing to point of a slight ping, no difference so not from timing being retarded.

3. when temp got to two thirds after some hard (but not heavy) driving, checked temp of headers ( have extractors and 3 inch system recently fitted) and they were around 400 degrees celsius!!! Don't know about you guys, but that seems a little excessive to me?? if so, it could be the fuel mixture being too lean as whyatts mentioned, which i guessing will have to drop into Whyatts to adjust if that is possible???

4. checked dizzy vacuum advance, appears may be stuffed, from memory i am sure if you try to draw air through it long enough, you will come to point where no more will come??? if so, then vac advance is stuffed. BUT will this cause it to get this hot?? seems like something very minor and struggle with the thought that this could destroy an engine from overheating it??

Next point of call will be to see if i have another fan belt to bypass the blower, which if it is vacuum advance or fuel mixture, it should stop as it wont require such advance/fuel, I think??:confused:

Forgot to mention, seems to be worse since i did service when i fitted radiator etc.. in service i included new distributor cap and rotor, new 8mm ngk leads and ngk iridium spark plugs... guessing with these spark plugs, if it already having a problem with a lean fuel mixture, the extra burn these plugs may give, may create even more heat??? just some further thoughts?????

[mike 90 RR]

3.it could be the fuel mixture being too lean as whyatts mentioned, which i guessing will have to drop into Whyatts to adjust if that is possible???

Yep to lean .... & Yep to seeking some mechanics input


4. checked dizzy vacuum advance, appears may be stuffed,
then vac advance is stuffed. BUT will this cause it to get this hot??

Yep .... and your gonna LUV the price of a new one ..... Install it before going any further

Your motor must of hit a Dyno when first set up .... The motor depends on ALL the correct parameters of fueling & Timing advance to run right ... When you ignite the blower // Your pushing the motor to the top end of it's original design .... The more HP you have ... The more CRITICAL is the tuning of the engine




Next point of call will be to see if i have another fan belt to bypass the blower, which if it is vacuum advance or fuel mixture, it should stop as it wont require such advance/fuel, I think??:confused:

Change the vacuum advance // if that doesn't work, then, I'ld stop mucking about with figuring it out yourself .... otherwise your gonna melt the motor

You need a Dyno ... or access to some electronic analysing gear to find out what the base points of your tune setup is or should be

[jmkoffice]

Bullfrog, Mike is correct. You have a unique vehicle here with a major operating problem. Problem/s that you will not be able to diagnose correctly to even start rectifying yourself. Spend the money and take it to a specialist.

Have a read of this post, it explans how important timing and fueling is for an engine operating correctly:

http://www.aulro.com/afvb/technical-chatter/88566-vacuum-advance.html

Good luck

[The Bullfrog]

Well, all is now sorted.

My first consideration in that the old viscous unit was faulty, was correct and this has been the problem the whole time!!!

My brand new viscous unit, just did not seem to be acting right, so after discussing with Steve at Whyatt's automotive in Geraldton, I went for a drive, got it hot (3/4) and went back to see what he thought.

Well, he confirmed my suspicion that my brand new viscous unit appeared stuffed!!!

Ordered a new one, fitted it today, and the needle didn't budge no matter what i did to it.

Though one other thing i found was that due to the supercharger installation, the temp switch for the electric fans was removed and disconnected so fans did not work unless air con was on.. no sorted this out with a switch on dash for those hard working times when air con not needed...

On a positive note, I have now gone through the whole car, know what it needs and doesn't and now know all that has been done to fit the supercharger, so it may have been a PITA, but there is always a positive to every story!!:)

[mike 90 RR]

Good to hear ... and glad you didn't fry the motor

May I suggest that you invest in a radiator with more cores in it, to keep the temp under control when we hit the 36+ degree days

Mike

[nice1guv]

Fantastic that it's running cool!

Goes to show, you can never rule out a new part as the problem!


hit the 36+ degree days

That's almost every day in Geraldton isn't it? :p