Help!!! Heaters cold on Discovery 300tdi

my heaters are blowing hot and cold - I hope I dont end up with all the arsing arounf you seem to be in the middle of, knowing my lucj though

Dent said:

Not much of a mechanic, no road test ? :doh: .

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He said he did do a road test, AND also left it running on the forecourt for over an hour!!!!!
Bit odd init!

Vik, the more i read of this thread the more you are having the same problem as me, i could leave the car running for a hour and not have any problems and also drive it round the block and have no problems, then all of a sudden on a short journey i would have it chucking water out of the expansion bottle or over heating completely!
I had it pressure tested and it came out ok, i had it block tested (sniff test) and that came out ok....took the head off to find it banana shaped!

D6Jay, I am beginning to think you are right! The car has been fine without the thermostat in prior to the P gasket being done but heaters are now blowing cold with the thermostat out (as I would expect) - but then when I go up a hill the heaters go warm and the temperature gauge drops back down to zero (the gauge was going up to half way with the thermostat out today??? BUT not going any further - very odd!)
The power is great, and there is no oil in the water, or water in the oil, and there is no coolant loss, or exhaust smoke, so I just dont understand how on earth it could be the head.
However I have found out that the head has previously been done and this has led me to beleive that it is perhaps warped, as I can see that the head gasket is not an original and what with all the other little bits that have gone wrong on this motor, I am tempted to beleive that the previous owner would not have had it skimmed!!!

I would suspect the water pump, it sounds like the impeller has become corroded or is slipping on the shaft.

Hi,
I have recently been running the motor with the expansion tank cap slightly loosened, and this seems to be allowing the engine to run up to temperature and NOT overheat (with the expansion tank cap on now, it blows back - the water pressurises and blows back out the expansion tank cap and will eventually overheat, and the thermostat housing again becomes dry!!!)
I have done this now for over 3 weeks or more, although we have only been doing local runs.
I think hubby is going to bite the bullet and strip the bloody thing this week, to see if it is blocked or if the head is warped!! I will post an update as soon as, or if anyone else has any ideas, please let me know.
Also, where am I best off getting a genuine gasket set from, heard a lot of bad reports about many dealers (especially the likes of paddocks etc)
Thanks
Vikki

viks3457 said:

Hi,
I have recently been running the motor with the expansion tank cap slightly loosened, and this seems to be allowing the engine to run up to temperature and NOT overheat (with the expansion tank cap on now, it blows back - the water pressurises and blows back out the expansion tank cap and will eventually overheat, and the thermostat housing again becomes dry!!!)
I have done this now for over 3 weeks or more, although we have only been doing local runs.
I think hubby is going to bite the bullet and strip the bloody thing this week, to see if it is blocked or if the head is warped!! I will post an update as soon as, or if anyone else has any ideas, please let me know.
Also, where am I best off getting a genuine gasket set from, heard a lot of bad reports about many dealers (especially the likes of paddocks etc)
Thanks
Vikki

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Hi Vikki, I've used Paddocks for 6 yrs now and found them to be great, not ALWAYS the cheapest but usually and they have huge stiocks of the everyday stuff.

Hello Viks3457

I know this problem to some degree as my Disco has the same problem and all the suggestions that have been made are very good and probably worth a try
But? and this is the question that i think you should have been asked have you done the test to see if the cooling system is working as it should! as I have been there already heater blowing hot then cold then hot however I had an air bubbling noise coming from area of the heater matrix before it would blow hot again! A CLUE! unless you are fortunate and just have sludge in the matrix I would try this test, with the engine cold take off the fan belt this is very easy and just requires bit of metal rod 10 mm dia about 600 mm long place it in the tensioner arm so that the arm can be lifted by pressing down on the rod slip the
fan belt off! basically so that the pump is not pushing water around the system
(i would take the belt off the car altogether to avoid any snagging problems)
next take the cap off of the expansion tank start the engine and watch the water level, if the water level starts to rise you have the answer, it shoudn't take long to start rising! you can run the engine for at 5 mins or so with out the pump! back to the story if as I suspect the water level starts the rise and there is no pump to push water against a blockage in the system then the only thing that can make the water level rise is air being pushed into the cooling system via a breach in the head gaskit at best! or a crack in the block or head! the bottom line is the cooling system must be in good order?
before moving on to the other possible problems that can exist? if its just sludge in the matrix then taking both pipes off and back flushing with a hose pipe will normally sort it out? also be aware that on a car of that age the radiator core can be the cause of all ills! if the core is weeping slightly the
coolant level will drop over a period of time this can allow the pump to run dry
and destroy its self by this time damage may also have occurred to the head etc. and during all this the temp gauge says all is well? mine did? hopefully this information is of some help to some body (a radiator costs about £100 if your car is running fine but your not sure about the rad £100 is a cheap service?)

viks3457 said:

Although I have to say, once it was tightened the thermostat bleeding plug seemed to be hissing a little, which i am presuming can let air in!!!!

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I assume you still have the ****e plastic plugs fitted... nip to b&q and buy 2 radiator plugs (you can even buy one with bleed screw if you really want) for £1.50 a piece, wrap a bit of PTFE tape round the threads before fitting and that may make all the difference.

HI,
Thanks for the replies. I have only just read them, unfortunately after hubby has decided to take head off.
He has taken it off, but all the bolts for the exhaust manifold etc were able to be undone with his hands!!!! That just obviously wasn't right to start with.
When the gasket came off (sorry if these aren't the right terms for the things but I just call them as I see them) the right hand side was fastened good to the head, and the left hand side was free, came away from the head easy as pie, and the central bit under the gasket was black. I am presuming that this was our problem. It seems that it isn't warped, so hubby putting it back on today.
Is there any tricks we need to know before he starts, or anything he should avoid (he obviously knows about the bolt order etc, but didn't know if there was a knack to something that maybe he should know about!!!)
Thanks in advance.
Vikki x

Well head gasket replaced, and all put back together. bled up and quick drive down the road, got 300 metres and there was a "pop" and low and behold the car cut out and there is an unbeleivable amount of oil seeming to be coming out of the area of the head at the front next to the thermostat housing, I mean, thisleak is spraying so bad, its over the outside of the motor, all over the expansion tank.
Any ideas, have we blown the head, or the new head gasket???
It is currently majorly cold up here, could the ice have caused something??
Please can someone give me an idea what to do. I can't see exactly where it is coming from, just that is seems to be coming from the front end of the head, just below the thermostat housing!
Thanks in advance
Vikki x x x

eeek you are having some time with it...

Think we have sorted it - looks like the torque wrench we used hasn't torqued it properly. Going to re-do tomorrow - will post once we have sorted!!!
Fingers crossed x

viks3457 said:

Think we have sorted it - looks like the torque wrench we used hasn't torqued it properly. Going to re-do tomorrow - will post once we have sorted!!!
Fingers crossed x

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I hope that's all it is...you may have the head gasket on the wrong way up and wrong way round

Once the head has come off again (as the oil kept leaking out) the head bolt snapped and the front tiny corner is quite clearly seen on the corner of the head as the offending gap!!!!! no where else.
New torque wrench, new gasket and cleaned the head, going to put back on!!!
We only went 200 yds and this happened, no heat on gauge (moved but not even over the first mark) and no obvious sight problems with the head! No oil contamination (i.e. oil is black not milkshake coloured) water is not oil coloured, and no white smoke out of exhaust. Engine was shut down as quick as leak started. What are the chances of this being warped!!!!
Thanks for all your patience.
Vikki x

Well, low and behold, we handed the head over to the pro's and it was indeed warped. They had to take a mm off it!! It is now all back together and working fine.
Head gasket had indeed failed, head had indeed warped, and now we have lovely warm heaters!!!!! (hopefully permanently)
So after all this it was the head (although the P gasket and other things definately needed doing and the alternator is going to need doing as the bearings are on their way out apparently), so as much as we wanted it not to be, if you think it is the head, it usually is!!!!!
Thanks for everyone's advice, it's been invaluable.
Vikki,

Just sat down and read this two month tale of doom! I do hope you have now resolved all your issues, my thoughts are with you over this.
I have a 300 tdi myself, aso I am taking note of this just in case, but so far my only issue has been the previous owner removing the thermostat and this is my first winter with the car - amazing how fast you get one fitted!!!
Best wishes, thanks for sharing this.

Richard Martin said:

I hope that's all it is...you may have the head gasket on the wrong way up and wrong way round

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You were right - head gasket was on incorrectly

Hi Vik, I had the same problem on my disco v8 it was the heater matrix, they cost about 45 quid and got mine off ebay, the only pain is that its a full dash board out job to fit it in so hopefully you have a mechanic friend to do it for you as it is quite fiddly!!and labour intensive !!Hope this helps K

kerry4x4 said:

Hi Vik, I had the same problem on my disco v8 it was the heater matrix, they cost about 45 quid and got mine off ebay, the only pain is that its a full dash board out job to fit it in so hopefully you have a mechanic friend to do it for you as it is quite fiddly!!and labour intensive !!Hope this helps K

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I really hope your right - I have put another thread on here, as my heaters are still cold, hubby is trying a new thermostat today, in the hopes that this is causing the problem.
The pipe from the thermostat housing to the rad is warm but not red hot, and the one from the bottom of the rad is cold (as is the water in the expansion tank)!!!! UNTIL the engine is turned off, then the bottom hose goes warm and the expansion tank goes warm too!! Some one has said to me that the thermostat could be stuck open slightly and therefore water is running constantly!! I'm totally at a loss. We had both pipes at the heater matrix warm yesterday for about 1 minute at 3,000 revs, but the heaters went to about a degree watmer than aired!!! More heat off a match!
It's driving me crazy, and I'm constantly shivering!!!!!!!