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2.5TDi (and others) Thermostats

Discussion in 'A4/S4 forum(B5 Chassis)' started by PAULF, May 24, 2012.

  1. PAULF

    PAULF Active Member
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    I have had a problem with my thermostat for a while now, and the cam belt is not due for change for a couple of years.
    I know that I can change the 'stat in a weekend, but after reading many posts here and elsewhere about new stats failing early, I looked for a solution

    The best write-up I have found is here Diesel thermostat definative answer , which, although over a hundred pages, is worth reading. Scrag, on the B6 forum has also had a look at this, and used a Renault 5 type 'stat here 2.5tdi changing thermostat - whats involved?

    I have gone for a more expensive, maintenance friendly solution - a remote thermostat.

    I sourced the manufacture of the housing from Classic Mini Parts | Titanium Components | Force Racing. Carl was a great help, and produced a nice bit of kit.

    I decided to fit the housing and 'stat in the top hose, using the coolant return to provide flow past the bulb. Here is the unmodified hose

    [​IMG]

    The recommended 'stats were from a Suzuki Swift, 1, 0 or 1.3 litre, 44mm OD, part no 10/84-02/89 for 82 degrees, part no, 03/89-12/03 for 88 degrees. I bought the 88 degree one.
    I then fitted the stat into the housing

    [​IMG]

    and screwed the halves together. This took a bit of fiddling, as there is a 'jiggle' pin that aids air removal that you want to keep at the top - it can just be seen here by the 10mm outlet

    [​IMG]

    There was more pratting about with sealing - I use a green pressure plumbing sealant - and then the unit can be fitted

    [​IMG]

    I then left it to idle whilst I checked for leaks (and rectified them!) and then the test -

    [​IMG]

    I have now ran the car about 100 miles, and it stays bang on 90 degrees.
     
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  3. scrag

    scrag New Member

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    that is a job very well done boss!!!!
    excellent write up too!
    I've stopped counting the miles I've done since my inline thermo,it takes about 3 miles to warm up to 89 degrees but then sits there at tick over or at 80mph.....
    your all set for winter now mate,warm feet and a more fuel efficient car!
    cheers
     
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  4. aragorn

    aragorn "Stick a V8 in it!"
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    thats awesome!

    My only concern would be the time taken for the heat to make its way along that hose.

    With the stock thermostat, its in the water flow all the time, as it sits in the V right beside the water pump. So as soon as the temp hits 90c (or whatever) the stat will open.

    With the remote stat, the heat has to make its way along a couple feet of hose, with no water flow, before the stat will open... So its possible that if the heat rises quickly (say you boot it down the motorway) it could take a while before the heat conducts along the hose and the stat opens...

    I wonder if the "jiggle pin" lets a small amount of water past all the time, allowing the stat to see the real water temp faster?
     
  5. PAULF

    PAULF Active Member
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    The position in the top hose gives a constant flow through the coolant reservoir which, coupled with the 'jiggle pin', allows flow across the bulb. The temp rises steadily to 90 degrees, then stops bang on - and it's been hot outside for the first week!

    When I first tried it, the stat moved in the housing and didn't seat properly, it took forever to heat up, not really making 90. That was purely down to the extra flow past the stat. As long as the temp gauge reads between 80 and 100 degrees, I'm happy, but to see it vertical at 90 is great. Is should be a simple task to replace it when it inevitably goes too.
     
  6. aragorn

    aragorn "Stick a V8 in it!"
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    well the guage shows 90 at any temp between 80 and 100c anyway :p
     
  7. PAULF

    PAULF Active Member
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    :lmfao:

    Interestingly enough, Scrags fix warms up faster than mine. It takes about 10 mins to reach temperature. I suspect this is due to the increased unregulated flow through the coolant reservoir coupled with the designed flow through the 'jiggle pin hole'. :readit:
     
  8. aragorn

    aragorn "Stick a V8 in it!"
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    depends how and where your driving it, more load means more heat etc.

    If your first 10mins involves light throttle down a Basra-esque farm track, and Scrags is streight out onto a dual carridgeway and upto 80mph, yours is obviously going to take a lot longer to warm up!
     
  9. PAULF

    PAULF Active Member
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    Fair comment,

    (although how do you think I ended up airborne and bent the Panzer Plate?) :racer::superman::sob:
     
  10. Mackers

    Mackers Member

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    hi again paul (3 times now i think) what is the I.D. of the tophose??
     
  11. PAULF

    PAULF Active Member
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    The top hose ID is about 28mm, and the coolant reservoir hose (the small one) is 10mm. (At least, that was the pipe sizes)

    I had a 1mm lip on the housing to aid the jubilee clip to hold.
     
  12. Mackers

    Mackers Member

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    i'm thinking of the volvo340 'stat as it operates higher than the Ren5.
     
  13. PAULF

    PAULF Active Member
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    I think that's what Scrag used in his thread.

    Read what he did - I think he put it in the top hose but at the bottom, by the engine.

    Also have a good read of the Rover thread it's quite interesting!
     
  14. Mackers

    Mackers Member

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    i have done.... well most of the rover one, the scrag one i think is brill, i may "upgrade" to your method in the summer,
     
  15. Ian2012

    Ian2012 Active Member

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    So how do i go about buying the necessary bits to do my car which is a v6 petrol a4 the top hose looks the same as in the picture
     
  16. adamss24

    adamss24 Well-Known Member

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    pm sent...
     
  17. Mackers

    Mackers Member

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    adamss24.... got any hints for me too plsssss :p
     
  18. adamss24

    adamss24 Well-Known Member

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    Yes mate, do it properly for 130 quid supply and fit genuine thermostat and seal...just like the factory intended !
     
  19. nedge2k

    nedge2k Member

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    Noticed mine wasn't going above 70 degrees, plumbed this in today with an 88 degree stat and it's maxing out at 95, dropping to 85 at idle.

    Rover K-Series | QED Remote Thermostat Housing | QED Motorsport | Ther

    NB - it's made to take 32mm ID hose and an 8mm return. The 2.5 hoses just squeezed on and I replaced the return fitting with a 10mm. Cost me nothing and works a treat :)
     
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  20. trawicki1

    trawicki1 New Member

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    nedge, do you have some picture please? i am looking to do it this way, also were your hoses 28mm ID?

    many thanks
     
  21. nedge2k

    nedge2k Member

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    Didn't measure my hoses, just went on what Paul said and figured I'd be able to squeeze them on. 28-30mm is about right.

    My 10mm return fitting went in nice and snugly.

    The most i've seem my temp climb to so far (with the 88° stat) is 99° under hard load - but a 50/50 G12 mix shouldn't boil until 107°. I'm happy :)

    IMAG0677.jpg
     
    #20 nedge2k, Nov 11, 2013
    Last edited: Nov 11, 2013
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  23. trawicki1

    trawicki1 New Member

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    many thanks, looks like you have an extra return hose than me, i dont think i would need the t piece
     
  24. nedge2k

    nedge2k Member

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    I just used the QED housing, that t-piece is factory.
     
  25. trawicki1

    trawicki1 New Member

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    mine doesnt have the t piece in at all so would just be the housing, thanks for your help
     
  26. PAULF

    PAULF Active Member
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    Nice job Nedge, mine is still going strong after 18 months and 20-30'000 miles.

    I'm in the process of doing my belts, so I am changing the stat too. I will still keep my inline one as a backup though.

    One thing I will say is the one I had made was about £80 IIRC, so a bit cheaper than the Elise one. The Rover site has links to a few housing manufacturers, but I went with the cheapest!

    Be careful Trawaki, without the Tee giving an constant flow past the stat bulb via the coolant expansion tank you may find the stat doesn't heat up enough to open. If the stat you use has a jiggle pin or hole you may be ok. Alternatively drill a small hole in the stat flange to give a small flow. See the Rover thread for more info.
     
    #24 PAULF, Nov 11, 2013
    Last edited: Nov 11, 2013
  27. trawicki1

    trawicki1 New Member

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    it will have the return pipe back to reservoir, i am in conatc with carl and looking to get the same as yours, and from the pics yours looks identical pre mod as mine.

    i am new to these cars so am finding my way, i have read a bit about the viscous fan, should the fan be spinning from cold? forgive me if this is a silly question
     
  28. trawicki1

    trawicki1 New Member

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    have just noticed yours also has the t piece paul. mine has no t piece and just has the return pipe from the top hose going straight into the header tank. i guess it will still work fine if plumbed in as yours is
     
  29. nedge2k

    nedge2k Member

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    yeah all viscous fans behave that way. when cold you should be able to stop it by hand if it is correctly. still not a great design though, replace with electric to free up some ponies.
     
  30. PAULF

    PAULF Active Member
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    As long as the 10mm hose goes from the 'hot' (engine) side of the housing to the expansion tank it should be fine.
    There will be flow past the 'stat bulb which will open when it reaches it's set temp.

    The fan will spin at idle with very little cooling effect due to the inherent friction in the viscous coupling.
    A real man will test it with his fingers - if you still have them afterwards, the coupling is ok.

    A sensible man will shove a copy of Womans Own magazine into the fan slowly after starting the engine from cold. If it gets shredded, the coupling is broken. If the fan stops, the coupling is fine.
     
  31. trawicki1

    trawicki1 New Member

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    i wil try the fan test tomorrow, but dont think i will use my fingers as it seems to be spinning very fast, it spins freely when the engine is off as i have spun it by hand then, i take it if the fan is overspinning that is another big job to do that involve removing the front end?
     
  32. QuattroFreak

    QuattroFreak Member

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    Bit of a dumb question maybe but can any of you show me a picture of how the R5/340 stat has been inserted? Which end faces where? and what is all this about cutting the hose? Why? Where? What's used to seal it afterwards?
     
  33. slepy

    slepy Extremely smart and handsome person.
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    Not sure if that's the same as you have, but it should be rather simple to work out which way it goes in.
    [​IMG]
     
  34. QuattroFreak

    QuattroFreak Member

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    :encouragement:
     
  35. S4_dan

    S4_dan Fire up the Quattro!
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    I think @QuattroFreak was referring to the addition of the Renault 5 / Vovlo 340 'stat which is fitted into the radiator hose.....

    There is a good guide somewhere on here or google.
     
  36. QuattroFreak

    QuattroFreak Member

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    ^^^ What @S4_dan said ^^^

    At least I know now which direction it should be facing, all I need to know is where to cut, how to fix back together!!

    Thanks!
     
  37. QuattroFreak

    QuattroFreak Member

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    Also, I can see here that there are 2 hoses on the right and 1 hose (radiator or block) on the left in the first (untouched) photo.

    What are the internal dimensions of each of those hoses?

    I have read the rad hose is 28mm (ID) and the top hose is 10mm, maybe 15mm the bottom hose?

    Can someone shed some light as I am sure rover had a 3 way thermostat housing of that sort??

    Cheers
     
  38. QuattroFreak

    QuattroFreak Member

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    OK, so I had a look at mine today, maybe someone can shed some light as to where I must cut and insert, here's a few pics of mine:

    Heres the connection to the radiator:

    [​IMG]


    The main hose seems to flow from the expansion tank down but not straight to the radiator:

    [​IMG]


    {The arrows indicate coolant flow direction}

    I cannot see, as you have done in this how to, how or where I should insert the thermostat unless I just place it straight into the radiator hose or even the bottom radiator hose.

    Other than that, all I can see is that I would have to make some sort of auxiliary housing for the thermostat and change the location of the return hose.

    Any suggestions?

    Sorry, mine is the AKE 2002, this may have been based on a B5 as the hose locations differ (from what I can see).

    Thanks again!
     
  39. QuattroFreak

    QuattroFreak Member

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    Ha, just noticed the forum it was listed in, DUH! :keule:
     
  40. adamss24

    adamss24 Well-Known Member

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    Just do it properly mate, i hate bodges...
     

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