Thermostat Disco 2.5Tdi 300 series

Hi,

Have just changed the thermostat on mine (also disco 300tdi).

It is very easy.

1. Take of the coolant hose (short one from thermostat housing).
2. Take off small rubber hose.
3. Release two bolts at the side.
4. Pull of side of housing.
5. You will then see the top of the radiator. Take it out, making sure you remove the rubber gasket/ring as well.
6. Put in the new thermostat (same orientation as old) with new rubber ring.
7. Put everything back together.
8. Add some coolant as needed.
9. Make sure that everything works and there are no airlocks, by running engine until normal temperature, and feel if the hose you have removed and replaced gets hot. It should after the thermostat opens. And of course, check for leaks.

Hope this helps,

Pieter

...and Pieter Vroom spake unto the tribes of Usenet, saying...

Don't forget to drain some coolant out first! Messy otherwise.

...and D@H spake unto the tribes of Usenet, saying...

What makes you think it's the thermostat? If these fail, it's usually either open (engine slow to warm up) or closed (engine overheats). I've never heard of one failing intermittently, and your symptoms seem variable. Irregular temperatures and blowing cool air sound very much like either a drastically low water level or air locks in the system. Neither will be affected by changing the thermostat.

Overheating a 300Tdi can wreck it very quickly - I would seek someone experienced to examine the problem and advise you what to do.

As Pieter says, changing the stat is pretty simple. Make sure you have a new gasket to put it all back together, and take care undoing the bolts that hold it on. They have a habit of seizing, and if you snap one off it's no end of a faff getting it out. If they are reluctant to come out, use plenty of penetrating fluid and try it the next day.

It is the things that cause faff,that Cost me excessive amounts of cash ;o)

I have assumed that it is the thermostat,naturally anything and everything with temperature led me to conclude this diagnosis.

I am so glad that I asked before I went in and made adjustments.

The tale to date is late last year(August) I managed to bugger my head gasket,I spent an horrendous amount of money having it towed in to an RAC approved garage,where upon my arrival,the mechanic/manager was delighted to see that christmas had arrived early and confidently told me what was required,backing up this explanation of masses of pictures showing rotation of serpentine belts and bent valve push rods.

This bought floods of sweat and panic upon me as within the same fortnight,I was due to expedite the south west with caravan,dog,wife & kids.

Not being a mechanic,and having friends who are not mechanically minded,I felt assured and clued up in the knowledge that all was well,and agreed the repairs to be undertaken and accepted the bill was not as much as facing exile from my family,even my dog would have ignored me forever,had the holiday been ruined. My disco was repaired and all seemed to be fine,bill paid and on our way we went.

4 Days into my annual,my cambelt gave up and through a relay service we were dispatched back home and into the garage that repaired the head gasket,with a complaint & enquirey why they did not replace the cambelt at the same time as the head gasket,to which I was told there was no need because the 300series Tdi had an 'internal routing'??? so I agreed again to pay for the repair of cambelt.and was allowed to return back to my annuals allover again. Things appeared to be fine and life returned back to normal in no time at all. Now as I only ever make small trips throughout the week and never have much need to go on trips that exceed 40mph,I have never really noticed the temperature. As the weather decidely got much cooler,naturally the tendancy is to operate the heating and get all cosy on nippy mornings,this is where I was aware of the temperature guage not working effectivly and there have been periods where the needle has gone off the scale,then dropped back to midway between cold and hot,but no heating at all making its way into the vehicle. After asking different people,each of them have concluded that it would be my thermostat and is a relativly simple thing to change.

I am not in a financial/trusting position to take back to Garage,as I left there smouldering after debating the cambelt/head gasket issue at great length,Where I feel they could have advised me from the first visit the full cost and repair work required.

My loss was there gain! Thanks for the fast responses,I look forwards again to further replies.

...and D@H spake unto the tribes of Usenet, saying...

Where are you? I am sure someone (if anyone's nearby) could be persuaded to pop over and have a look for the price of petrol and a cuppa on arrival. Sounds like you've had a bad experience.

In message , "D@H" writes

If you have already had the head gasket done then look from the passenger side of the car (RHD) at the side of the engine block.

Can you see coolant or signs of coolant streaming down the side of the block?

This is caused be a leaking "hockey stick gasket" And would give the symptoms you describe. Treat it with urgency as the loss of water from here on a 300tdi can leave the water pump spinning in free air causing the engine to melt very quickly.

Only takes 45 mins to change it (gasket not engine)

Good luck

I can see what looks like bird poo streaking down behind where you say,also,believe this,The expansion tank was dry,So looks like I have been given solid advice from Pieter,Richard & Marc.

Thanks for the offer of travelling to me Richard,that was a fantastic & kind offer.