V8 over heating

[disco-v8]

ok im having some trouble with my3.9 high compression V8..... well as you can tell by the title, my engine is over heating, it will be fine for about 45mins of driving, and the engine will be running fine at normal operating tempurature then susddenly the tempurature will rise making me stop and letting it cool down.....

The radiator is in great condition and doesnt leak, and the cooling system is full of water, the viscus fan is working and even my two small air con fans kick in but it still over heating!!!!!!  :o


its starting to worry me now as it stinks when it overheats and i can hear some hissing and bubbling which doesnt sound right.... i dont let it over heat completly because i dont want to damage the engine.....

also now and again after running it for a while it doesnt tick over properly and looks like its going to stall...


if anybody can please help then please do so, beacause im well confused

cheers in advance

[Range Rover Blues]

Air locks, the EFi is a b******** for them.  Fill the enine via that little brass plug atop the engine and once it gets hot bleed some air out of the top of the rad and the brass plug by cracking them open a turn.

Check your hoses are fully secure.

The cr4ppy running could be because the thermo sensor for the EFi is no longer in the water, it could be the fuel vapourising.

Where does the water acftually escape from?

Are you sure it's not a head gasket?

[disco-v8]

i always fill it up usuing that method, by filling it through the top of the radiator, and yep all my hoes are fine.......

im not realy losing much water that isnt realy a problem, i just have a few drops from my core plugs, thats why i need them replacing.  it get a bit worse when the engine is close to over heating though but not enough for me to get worryed....


its has always driped from them since owning the car about 2months ago and also it was running hot then, but not over heating, which i found out to be a dodgy vacuum advance and it was just sucking, so would have bin making the fuel mixer lean and running hot.... asoon as that was fixed the car ran great and with better MPG aswell... but now im getting a proper over heating problem

i do beileve the head gaskets do need replacing as ive already bought them with my core plugs...... when the engine was running hot last time because of the dodgy vacuum advance unit, it was making the gasket boil abit and making waater fizz out of it... if that makes sense

[Skibum346]

Disco,

You checked the obvious, thermostat?

If yer thermostat is staying closed no water gets to the engine and what is there will boil after a short time.

Had the same problm on my 1984 3.5.

Good luck

Skibum

[disco-v8]

no didnt check the thermostat, as i didnt think i needed to, because the radiator is getting stinking hot, so it must be open to allow the water to the cooling system

[Skibum346]

Disco,

Good point, but if the thermostat sin't fully closed, coolant flow is restricted, stays in the hot part of the engine longer and the radiator has to work harder to dissipate the heat.

For the cost of a thermostat and 5 minutes with a spanner it's a good thing to start with.

Up to you.

Good luck

Skibum

[suggs]

i had this problem was the thermostate ive removed it completly now, also could be the water pump on its way out, not circulating the coolent propley..does it overheat when your moving or only when your in traffic

silly question but i take it the rads clean, not been off roading recently

could even be the rad cap on the F&E tank..

H

[Range Rover Blues]

It's not so much the lean mixture that causes the overheating as the fact that the fuel is burning too late and therefore doesn't yeild as much power, subsequently you burn more fuel.  Consumtion any better now by any chance?

But you are right though, it would cause it.

So your engine is still full of water when it boils over? I think the weather has a lot to do with that, if it was getting warm a few months ago it will be going over the top now, you're not the only one to find that.

You said your rad is fine but have you flushed the system?  Does it over heat when stood or moving?

Mine got very hot today and I notice the fan got noisey.  Does your viscous fan make a noise when you first start then go quiet? it should start making that noise again as it get too hot, if not the fan isn't working properly.

[disco-v8]

 dodgy vacuum advance and it was just sucking, so would have bin making the fuel mixer lean and running hot.... asoon as that was fixed the car ran great and with better MPG aswell...

like i said before after i fixed the vacuum advance it got better MPG...



the radiator is definatly clean, because i took the whole of the front end of so i could clean it down with a hose pipe.  i could do an engine flush but im sure thats not going to do it, i just no these things and its not rite!!!!

ill change the thermostat tomorrow if i can get one localy, but the thought of the water pump not working was also i thought i had and it was getting the water around the system, but wouldnt that make a noise or soming where it had broke off?????

it doesnt matter if im driving or standing still after about 40mins the temp just goes up and wont come back down untill i pull up and let it cool down.... also its not the hot weather thats doing it because ive bin out in hotter weather down leciester when i went off roading for the first time and i wasnt moving that fast, and it never over heated then, and thats when i had my dodgy vacuum advance on!!!!

the viscus fan deffinatly does the fast spin when started beacause i like the sound of it untill it dies down, but im not sure if it does it when it hot??? but i dont think that matters as i never noticed it before when it didnt over heat and now it is over heating.... im deffinatly sure its something else!!!!!

thanks for all the help tho :)

[disco-v8]

ok i took the hole of the thermostat off today to see if that was the course of my over heating problem.....


i went for a long drive and even went down to my local landrover parts place to get a new thermostat ( £4.90 with gasket) and everything seemed great, was driving lovely, no over heating.. then suddenly at a set of light just as i pulled up to a stop, the revs went abit crazzy on me, it shat to about 1500 then droped below 500 then back up to 1500 then droped to less then 400 then it died on me......

i waited untill the lights changed then started it and pulled off, i then looked at my temperature gauge and it was rising again   looks like i may have needed a new thermastat but its not going to be the solution to my problem!!!!!


help is needed badly now!!!!!

[Skibum346]

From memory, we had a problem with lambda sensors on our 3.9 that caused the revving problem. The se4nsors were shot and were passing dodgy info back to the ECM. It as a result, was weakening the mix, then trying to recover the resulting stall... produced a symptom very similar to your description.

Might be worthwhile getting it in for a diagnostic. My local garage does it for £40... at least it would give you a better idea of what to chase.

Good luck.

Skibum

[suggs]

with the revs flying up and down then overheating it does sound like a sensor or ecu fault rather than just a cooling system problem, ive got to speak to my local landy specialist in the next day or too ill ask them what they think..

H

[disco-v8]

cheers suggs if you could do that, then that will be great!!!!!

i no the revs went up and down then it overheated, but i think that its more of its getting to hot thats upsetting the fueling or a sensor....

.... but im not 100% on that..... it just doesnt make sence????

by any chance do you think that it may be an oil starvation thats making the engine run hot, as it would be metal on metal, and thats y it takes a while for it to over heat?????


im just coming up with anything no as im well confused

if anyone else wants to give me some info then your more than welcome

cheers

[Range Rover Blues]

If you think it's the lamdas, disconnect them and change the tune select resistor to tell the ecu there are no lamdas fitted.

[disco-v8]

If you think it's the lamdas, disconnect them and change the tune select resistor to tell the ecu there are no lamdas fitted.

ok what do i have to do to try this then?????

[Range Rover Blues]

Disconnect the Lamdas at the back of the engine bay, you can follow the wiring up but mine have a white 3 pin plug if this helps.

Next to the ECU is a small resitor in clear haeat shring tubing, often looped round so that it fits onto a connector. Remove it and replace with one from a non-lamda car or replace the resitor with one of the correct value if you can solder.  The ECU then thinks it is a non-lamda car.  You could try just pulling the lamdas off, one at a time to see if it runs better as the ECU has a certain degree of redundancy in the programing, eg mine runs fine with no MAF sensor.

[Henry Webster]

Disconnect the Lamdas at the back of the engine bay, you can follow the wiring up but mine have a white 3 pin plug if this helps.

Next to the ECU is a small resitor in clear heat shring tubing, often looped round so that it fits onto a connector. Remove it and replace with one from a non-lamda car or replace the resitor with one of the correct value if you can solder.  The ECU then thinks it is a non-lamda car.  You could try just pulling the lamdas off, one at a time to see if it runs better as the ECU has a certain degree of redundancy in the programing, eg mine runs fine with no MAF sensor.

Absolutely correct - the engine in the racer now runs without lambda sensors because we replaced the 'tune resistor'.  Basically this selects which map the ECU uses.  I think that there are about 4 different maps in total on a 14CUX.

RRB - Your's may appear to run fine with no MAF sensor, but when I had one fail on the Welsh Hillrally last year and we disconnected it, whilst it went well enough it did run over-rich to protect the engine from leaning out.  Really stung the eyes after a few stages and we were pouring petrol in it like it was going out of fashion (well more than normal anyway!)  also fuelled up the plugs.

Don't know whether this will solve your problems though Disco-V8 its really difficult to diagnose these sorts of problems remotely.  I struggled with an overheating Tdi a while back, radiator looked fine and flushed ok, but it was not until I replaced it that I sorted the problem. It was missing some fins, just really difficult to see past the fan etc on the back!

[Range Rover Blues]

I get what you're saying there Henry but on the LSE I still have the lamdas connected, so the ECU has 2 ways of deriving the air/fuel ratio.  If you like the MAF is a pro-active measurement, the lamdas are reactive.  This is why MAF sensors are so much better than VAF sensors, to calculate the MAF an ECU needs MAP and ACT sensors too (manifold air pressure and air charge temperature).

[Henry Webster]

Fair point, but I would imagine that the ECu goes into safe mode if any one of its core sensors goes down.  I'd be surprised if it didn't go into safe mode if the MAF was disconnected.  They aren't that clever.

H

[Range Rover Blues]

I honestly don't know, it drinks like a fish all the time no matter how it's set up.

[Henry Webster]

Me neither!  I guess I shuld shut up, then!

I have the same drinking problem! :lol:

[Range Rover Blues]

:lol:

My solution, get it to drink something cheaper.  At least it's not noticeably worse with the caravan on.

[disco-v8]

ok im getting very worried no as, is still over heating and im worried i may be damaging the engine......


i had another attemp of trying to sort it out yesterday, buy cleaning every bit of dirt off the radiator, flushing the system out and refilling it, toping up the oil, and i even took off the plenum chamber to see if there was a blockage in the cooling pipes..... gave it a good cleaning aswell, as that camber had abit of oily crap in it.......

thought everything was working and that i had done it, then suddenly it got hot again   !!!!!!!

ok im sure its not the cooling system anymore and that its more an engine problem now.....  all the fans work to try and stop it from over heating, well not to sure if the viscus is working properly but its always spinning so cant be that bad, and also it has always bin the same and it didnt over heat then!!!!!!


today it wasnt running the best ive every seen it, as when i first started her up the revs went to about 1500 as she usualy does but instead of falling straight away it took several seconds to drop, and then it was done in stages..... also when driving today it doesnt want to idle very well and feels like it missing a cylender or something as it shaking abit, and then i hear a knock that sounds like its coming from the exhaust (or could even be the bottom end :shock: ) ..... it use to idle at about 550 RPM when in drive and about 625 when in neutral, but now after driving abit and then pulling up to a stop it will idle at about 675 then take some time to slowly drop!!!!!!!!!!!

another thing i have noticed to day was, when i pull up to a stop and it feels like its missing, i have to press the break peddle abit harder to try and stop it moving, as it wants to try and move forward but in pulses (like on a certain power stoke of one clender...if you know what i mean)


to day the engine was apsolulty stinking hot, and was near impossible to open the bonnet, but the cooling system wasnt overheating yet, and was at a normal temperature..... its as hot as it was when the vaccum advance wasnt working, but ive looked at that and thats fine.... im sure there isnt another air leak!!!!!!!

the thing is the car runs great when on the move and has loads of get up and go


does this ring any bells for anyone..... im trying to describe it as well as i can!!!!!

[Range Rover Blues]

The engine is hunting, that's why it creaps forwards in drive, don't worry about the box it's a symptom of the fast idle.

If it's misfiring there could be a running problem, an air leak in the inlet manifold, a clogged injector etc.  Keep an eye on the oil quality too, if it look cooked you have aproblem, run it on the thickest/best you can get in this weather.

A misfire could give you that knocking sound.  I accidentaly folded the top on the inlet manifol when re-nstalling the inlet and it gave me an air leak on 3 cylinders, some similarities to what you have described too.  Try a vacuum check on the engine at idle.

[disco-v8]

so whats the best way to do a vacuum test?????


and also what sort of code read can i buy to read my ECU which is alot cheaper than yours lol?????

[Range Rover Blues]

If I knew of one cheaper, I would have bought it

As for the vac test, diconnect the pipe to the fuel regulator at the back of the plenum and connect a vac guage to it.  Halfruads used to sell the Gunson's one which is callibrated (honest) with the results you would expect to get in various situations, expect it to read a little lower than callibrated though.

[disco-v8]

is that the pipe that goes to the fuel recirculating valve????

or the othere one that goes some where else along the bulk head?????

[nigel purnell]

I had exactly the same problem with my 3.9efi V8 Could not find the problem changed everything  then tried a new viscous fan  no more problems.The original looked fine and i thought it was working but when stationary did not provide enough puff  Nigel

[suggs]

mines going in tomorow for a fiddle, ill have an ask for you see what i can find out.

H