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2.5tdi changing thermostat - whats involved?

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by mystic.bertie, Oct 27, 2011.

  1. Turkster
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    Turkster Bro.Paul 2.5TDI Quattro Sport

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    [Feb 8, 2012]
    LoL, i missed all the fun,

    I said who ever said they could do that job in 1.5 hrs was on crack, not directed at any member here, Sorry if my words was miss read/taken,

    I have changed cam belts on Passat 1.9TDI's and it takes a fair few hours to take the front off and get at the cam belt, Iv not attempted a 2.5TDI yet, TBH i don't fancy it, So if anyone here can do a 2.5TDI cambelt change in 1.5 hours them id travel to see it done,

    quote me wrong but to do a thermostat change on a 2.5tdi then you got to take off the cam belt, i mean who would not if you have the car in that position ?


    on a lighter note, we can all, at times, not put down in writing what we mean in words, if you get my drift, So no offence taken as non was given with any malice, Im an English guy that lives out in Turkey on a rotational basis, so hence the nickname "Turkster" , I also don't mind people calling me names as i am a recovered drug user of the A classes, I cant remember if i ever tried crack myself but my past was rather hazy,

    Lets get back to the Thread in hand and "crack on" :beerchug:
    Last edited: Feb 8, 2012
    #41
  2. white.akita
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    white.akita Member

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    [Feb 9, 2012]
    would this work inline with the top radiator hose ?
    eBay - The UK's Online Marketplace

    my brother inlaw has a 2.5tdi with a faulty thermostat, may give the inline thermostat a try.
    Last edited: Feb 9, 2012
    #42
  3. scrag
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    scrag New Member

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    [Feb 19, 2012]
    cheers,just as an update,I've now done 1000 miles plus and no problems at all,i cleaned the throttle valve and the idling stutter has disappeared.
    there is no pressure build up behind the thermostat as i drilled a 2mm hole before i placed it in the hose.....

    i can honestly say to people with this problem who are on a budget to do this bodge/adaption without fear.....its a £5.49 fix!!!!!!

    get the volvo 340 thermostat as its 89 degrees.......the r5 gt turbo one is 88 degrees....some are 82.

    i did buy a spare hose from germany ebay,and have been carrying the tools to do a roadside swap........but now I'm 100% happy I will sell the hose with a 89 degree thermostat fitted as i did for cost price.......should anyone require it.......
    #43
  4. scrag
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    scrag New Member

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    [Feb 19, 2012]
    yes thats the r5 gt one that i bought from him......but i found a hotter one from a 340 volvo.....you can only push it in about 30mm from the engine stub end.....dont be shy boss......it works a treat.
    #44
  5. scrag
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    scrag New Member

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    [Feb 19, 2012]
    no worries,cheers.
    #45
  6. scrag
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    scrag New Member

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    [Feb 24, 2012]
    1361 miles an still going strong............
    #46
  7. scrag
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    scrag New Member

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    [Mar 12, 2012]
    2000 miles done now with no issues whatsoever...............
    #47
  8. PAULF
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    PAULF Active Member

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    [Mar 12, 2012]
    Well done, I think you can safely say you've cracked it! A stuck thermostat fix that cost a couple of pounds, instead of hundreds.
    I still want to try using a remote housing type fix, although I'm finding it difficult to get a spare top hose to chop up.
    I have been looking at this in some detail for a while now, and the Rover boys seem very happy with the type of fix you have.
    #48
  9. Turkster
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    Turkster Bro.Paul 2.5TDI Quattro Sport

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    [Mar 12, 2012]
    well iv not seen that one before, but if it gets you sorted until it is cam belt time then it gets my vote, :icon_thumright:
    #49
  10. hazpaker
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    hazpaker New Member

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    [Mar 18, 2012]
    i would have thought that the inline stat should be fitted into the bottom hose as that is the same hose as the original stat uses thus keeping the water flow correct, may be wrong though.
    #50
  11. scrag
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    scrag New Member

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    [Apr 25, 2012]
    oops have i put it in the wrong way for the flow then??????

    if i have she's still a runner with 3100 miles since i fitted it....

    i put it in the bottom of the hose that goes from the right hand side top of the radiator to a metal stub off the engine block.....its the hose thats got a feed to the reservoir bottle as well.....

    the temp sensor part of the thermostat is pointing down in towards the stub.

    off topic a bit but I've not long ago fitted a pierburg maf sensor..........what a fookin difference that makes eh!

    Pierburg Audi | Euro Car Parts UK’s No.1 Car Parts Retailer
    #51
  12. PAULF
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    PAULF Active Member

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    [Apr 25, 2012]
    I'm in the process of getting a remote housing made up for £80 to fit in the top hose. I'll post results when I'm done

    There is a lot of thoughts on hot or cold flow positioning, and it appears the jury is split. (along with the PRT style of stat)

    Personally I think so long as it opens at the right temps, it doesn't matter. Just check for hysteresis cycling if you are worried.
    #52
  13. adamss24
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    adamss24 Well-Known Member

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    [Apr 25, 2012]
    If you could get the car down to london i could fit you a new thermostat for £100 !
    #53
  14. PAULF
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    PAULF Active Member

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    [Apr 26, 2012]
    Cheers Chris, but it's a bit far - I'd be a few hundred in Diesel!

    I could do it myself, but I liked the idea of the remote stat as it makes it really easy to change again if required, and by the sound of things, even a new OE stat has a good chance of not making it as long as the belt.
    The Rover boys had a similar difficulty - as did the Elise, and came up with a number of fixes. I get the distinct impression that the manufacture of thermostats (along with much else) has taken a turn for the worse wherever you get them from! (Ask Diesel Bob about Bosch nozzles that turned out to be made under license in India - I was lucky he is thorough and found fault before sending them to me)
    Once I get my housing, I'll post on the B5 forum with pics and links and give updates - like Scrag has had the good grace to do.


    I'm hoping I'll get it next week and fit it then, as I have some ARBs to fit, along with best part of a grands-worth of front and rear arms and bushes!
    Last edited: Apr 26, 2012
    #54
  15. adamss24
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    adamss24 Well-Known Member

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    [Apr 26, 2012]
    I would rather buy the workshop manual and a set of locking tools and do-it yourself in a weekend. Funny you mentioned the India made bosch nozzles, a few years ago i had a Fiesta Courier Van which was smoking due to one injector not spraying right, bought a set of brand new injectors from Ford/Dagenham Motors and fitted it only to find out that the engine was running worse than on the 200k miles nozzles. Looked for a 2nd hand set of nozzles made in Germany and had no more trouble since + the engine done another 100k on them ! The genuine set was made in France and they lasted long enough !
    #55
  16. Pawel1
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    Pawel1 New Member

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    [Apr 27, 2012]
    2.5tdi 180hp
    Hi. I got this same problem with thermostat for last 5-6 months. Also have to add about 0.3l of coolant every 400 miles as it showing low. Is this could be only thermostat or there could be a problem with water pump too?
    1 more couestion. How offen timing belt have to be changed on this engine as i got various diffrent informations about it and i'm not sure.
    Last edited: Apr 28, 2012
    #56
  17. scrag
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    scrag New Member

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    [May 6, 2012]
    the following is a generalisation of a cooling system.....i hope audi v6s are the same......mines done 3600 miles since i put my thermostat in my top hose.....still no issues.

    A thermostat is placed between the engine and the radiator to make sure that the coolant stays above a certain preset temperature. If the coolant temperature falls below this temperature, the thermostat blocks the coolant flow to the radiator, forcing the fluid instead through a bypass directly back to the engine. The coolant will continue to circulate like this until it reaches the design temperature, at which point, the thermostat will open a valve and allow the coolant back through the radiator.​
    In order to prevent the coolant from boiling, the cooling system is designed to be pressurized. Under pressure, the boiling point of the coolant is raised considerably. However, too much pressure will cause hoses and other parts to burst, so a system is needed to relieve pressure if it exceeds a certain point. The job of maintaining the pressure in the cooling system belongs to the radiator cap. The cap is designed to release pressure if it reaches the specified upper limit that the system was designed to handle. Prior to the '70s, the cap would release this extra pressure to the pavement. Since then, a system was added to capture any released fluid and store it temporarily in a reserve tank. This fluid would then return to the cooling system after the engine cooled down. This is what is called a closed cooling system.
    Circulation
    The coolant follows a path that takes it from the water pump, through passages inside the engine block where it collects the heat produced by the cylinders. It then flows up to the cylinder head (or heads in a V type engine) where it collects more heat from the combustion chambers. It then flows out past the thermostat (if the thermostat is opened to allow the fluid to pass), through the upper radiator hose and into the radiator. The coolant flows through the thin flattened tubes that make up the core of the radiator and is cooled by the air flow through the radiator. From there, it flows out of the radiator, through the lower radiator hose and back to the water pump. By this time, the coolant is cooled off and ready to collect more heat from the engine.

    The capacity of the system is engineered for the type and size of the engine and the work load that it is expected to undergo. Obviously, the cooling system for a larger, more powerful V8 engine in a heavy vehicle will need considerably more capacity then a compact car with a small 4 cylinder engine. On a large vehicle, the radiator is larger with many more tubes for the coolant to flow through. The radiator is also wider and taller to capture more air flow entering the vehicle from the grill in front.


    #57
  18. wesmaster
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    wesmaster Member

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    [May 6, 2012]
    Just had the job done properly, Thanks to Adamss24! Would recommend his work to everybody! Car even seems to run better.
    Cheers.
    Wes
    #58
  19. scrag
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    scrag New Member

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    [May 7, 2012]
    aye they run better when up to temperature eh......
    did you replace the thermostat alone or have a cam belt change as well?
    #59
  20. PAULF
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    PAULF Active Member

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    [May 24, 2012]
    #60
  21. adamss24
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    adamss24 Well-Known Member

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    [May 24, 2012]
    We replaced everything needed ! Funny, Wes had a invoice from previous owner that the cambelt and ancillaries was replaced a year or so. On inspection it was only the belt that was new, the rest of the pulleys were still old- made in 2004- probably that's when it had it's first cambelt job.
    I even had fun taking the viscous fan off the car, some smart mechanic threadlocked it on the spindle. Ended using parts off one of my cars to get him mobile as the shops were closed due to bank holiday !
    #61
  22. PAULF
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    PAULF Active Member

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    [May 24, 2012]

    That's the problem, Chris, you hit unforeseen snags every time when you do large jobs.

    You have the experience and spares to get by this that most of us don't, as we may only do the job once every couple of years. For me (and I would guess Scrag) we've tried to eliminate the problem of the thermostat failing - or in my case at least make it less difficult to sort if it does go. Scrags fix cost about £10, mine was more at about £90 all in. I can now unscrew the housing and fit a new 'stat for the cost of the 'stat and sealant. I lose very little coolant if I use hose clamps, and the job takes about 20 mins - of course, if the thermostat is made properly, I'll not have to do it again.............

    For members in your area, your price for the job is very good, but a lot of us don't have access to such a known quantity as yourself
    #62
  23. GG61266
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    GG61266 New Member

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    [Jun 7, 2012]
    A4 2.5 tdi B5 Just had whole shebang to renew thermostat but now low on power how can I use vagcom software to do pump
    #63
  24. PAULF
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    PAULF Active Member

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    [Jun 7, 2012]
    Firstly, GIYF on this subject!
    Check in the VCDS forum, but unless VCDS Lite has been changed, for the 2.5 engine you need full VCDS for the TDi timing chart. Run the engine to temp (with your new stat!) then basic settings, block 4 and select TDi timing chart. Select AFB (or whatever) from the drop-down menu, and check the timing is within the lines. If not, stop the engine, slacken the three bolts on the pump pulley and adjust. Repeat until it is where you want it.

    With VCDS Lite (if it still doesn't have the 2.5 chart) you can go to basic settings, block 4 and there is a spec for the advance and retard. If out of spec, adjust as above to bring the numbers into spec.

    I can't remember the spec, and don't have time now to check on ElsaWin, but hopefully Chris will be able to give you more info
    #64
  25. GG61266
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    GG61266 New Member

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    [Jun 12, 2012]
    Many thanks car runs smothly just lacks that torque that bits when pulling hard
    #65
  26. phatsam
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    phatsam New Member

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    [Oct 2, 2012]
    Hi there, my thermostat is stuck open and was looking to fit a Renault thermostat into the top hose like scrag. I bought the Renault thermostat but it's far to big to fit inside the top hose. Can anyone offer any advise on how you can fit it?

    Cheers, Sam
    #66
  27. PAULF
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    PAULF Active Member

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    [Oct 3, 2012]
    Hopefully Scrag will come along with gen, but if you read through the Rover thread I've linked to in my thread, some of them ground down the edge to get it to fit in their hose.

    Of course, I am assuming you got the correct thermostat (I don't know exactly which one Scrag fitted)
    #67
  28. phatsam
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    phatsam New Member

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    [Oct 3, 2012]
    Ahhhh right, ill be sure to look over the Rover thread. I've got the Renault GT turbo thermostat, I think that was the correct one.

    I prefer your solution but unfortunately I don't have the funds at the moment.

    I tried sending Scrag a PM but It didn't send, I'm guessing you need a certain amount of posts before you can send PM's
    #68
  29. Grant_H
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    Grant_H Member

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    [Dec 1, 2012]
    Hello,

    I'm having the same problem - getting the cambelt done next year but would love to do this mod as a back-up for now.

    I'm pretty new to Audi's s would love some detailed pics / how to.

    Regards,

    Grant
    #69
  30. PAULF
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    PAULF Active Member

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    [Dec 1, 2012]
    I have pics/how to for my solution here, 2.5TDi (and others) Thermostats , and in the post is a link to the rover forum, where there are other pics and gen.
    #70
  31. Turkster
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    Turkster Bro.Paul 2.5TDI Quattro Sport

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  32. PAULF
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    PAULF Active Member

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    [Dec 2, 2012]
    I would think so.
    The hose was 28mm, IIRC, or at least the housing part was for that size. I used a 10mm outlet in front of the thermostat to allow a flow around the bulb, but reading the Rover thread, I would expect there to be enough flow through if you drilled a 1/8" or so hole in the 'stat flange.
    Last edited: Dec 2, 2012
    #72
  33. Mackers
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    Mackers Member

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    [Jan 21, 2013]
    #73
  34. steamship
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    steamship Active Member

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    [Jan 21, 2013]
    I too would be keen to get instructions on 'scrags' fix for this, as mine hasn't worked since I got the car some months ago.

    But then, there are lots of things that don't work on my car as it looks like it's never been cared for. Just removed the pollen filter which had a manufacturing date of 2005. :crying:
    #74
  35. PAULF
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    PAULF Active Member

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    [Feb 25, 2013]
    I think that Scrags fix may not work on all V6 2.5 TDi engines.

    Mine is an AFB engine on the B5s, and I got a 88 degree volvo stat (similar to the one in Makers link) to try on the other car.
    I have a spare top hose to try, and there is no way it will fit. The stat is 40mm-ish, whereas the hose is nearer 30mm at the bottom where it fits onto the engine - and I would guess it is probably 28mm up inside, past the point it fits over the engine pipe.
    I tried heating the hose in boiling water, and only just managed to get it started - no way would it go far enough in.
    I suspect there was a change at some point and the later cars may have had a larger bore hose.

    BTW, my volvo stat was only a fiver from the local factors!

    Oh well, off to Carl at Force racing for another housing!
    #75

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