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Td5 oil cooler repair (oil in coolant)

Discussion in 'TD5' started by MTurri, Oct 7, 2012.

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  1. MTurri

    MTurri Active Member

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    This post is about my experience fixing the classic oil-in-coolant problem that many Td5 owners run into. This happened some 2-years ago, but finally going out to the press.

    It all started with the usual oil stain in the expansion tank (aka coolant reservoir). It did not take very long for the stain to become a 1/8" thick oil film on top of the coolant which forced me to tackle the problem immediately. According to RAVE and own measurements oil pressure peaks at ~3 bar (when engine cold) whereas maximum coolant pressure is set by the expansion tank relief valve at about 1.4 bar (engine hot). The leak path is then obvious, engine oil goes into the coolant and not the other way around.

    After draining all engine coolant took out viscous fan, poly-v belt, turbo hoses, turbo and exhaust manifold. Released A/C compressor and carefully moved out of the way (piping still attached). Then did away with oil filter & housing and centrifugal filter & housing, and finally removed the oil cooler assembly.

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    At first sight I could not see where the leak was coming from, so undid the (2) hollow bolts that hold the heat exchanger on to the cooler housing to further investigate. Immediately noticed that the heat exchanger o-rings where deformed (flattened) and hardened, and also that there were oil marks in the oil cooler casing areas against which the o-rings seal.

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    The heat exchanger did not seem to be leaking at all, but wanted to have assurance around that. Based on the numbers above, the maximum pressure differential that the element sees is when the engine is started from cold, i.e. 3 bar inside the element and ~nil on the outside (assuming all relative pressures).

    To have the test done, sourced bolts identical in size/thread as those used to attach the heat exchange on to the oil cooler housing. The bolts I could get my hands on were longer than needed so had to cut them back to the required length; in addition one of them was drilled through and tapped to a 1/4" NPT (F) thread.

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    Using hose and various compressed air type fittings, rigged the following up:

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    The heat exchanger element was then successfully tested to just above 3.5 bar (thought about going higher but did not want to push my luck).

    [​IMG]

    More testing: with new o-rings on the heat exchanger and using the specially developed bolts, tested sealing integrity of the 'radiator' against the housing (I know... only partially valid as bolts have to come off).

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    Regrettably, I did not take note of either bolt or o-ring sizes. The o-rings I was able to source at that point were not Viton (FKM) as they should be for this kind of application (hot hydrocarbons), but regular Buna rubber ones (aka Nitrile or NBR). In all honesty I was expecting that they would not last long and that I would soon be dealing with this issue again thus having a chance to check o-ring sizing, but today some 70K later they are still going.

    I suppose I was lucky in that there was nothing wrong with my 'oil radiator' since these were hard if not impossible to get a hold of back then, and needless to say a replacement oil cooler assembly was and still is worth a small fortune. The blue brand with the bad name now sells the heat exchanger as a separate part (p/n DA1127) although they don't come cheap either.


    Regards
    Matt
     
  2. Shifty1962

    Shifty1962 Well-Known Member

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    Nicely done.
     
  3. Dublindisco

    Dublindisco Active Member

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    Hey thanks for the write up.

    Got as everything off today up to the oil cooler. Mine has a leak of coolant closest to the water pump.

    Is there a gasket on this that could be leaking coolant on mine?

    To be honest the hardest part of the job was removing the nut closest to the engine under the centrefugal oil filter, to release the actual filter head itself.

    Took me about 45 mins as i had no ratcheting spanner.


    So gonna whip the cooler off tmrw and hopefully my coolant leak will be blatently obvious... like a gasket or something.

    This is as far as i got today.

    [​IMG]

    [​IMG]
     
  4. Dublindisco

    Dublindisco Active Member

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    Managed to get the oil cooller off today.

    Doesnt seem to be a gasket on it or else the old one has completely disintegrated. Have ordered one online for a fiver.

    Also seeing as I have 150k on the clock I ordered a new water pump.

    Seeing as I had everything else off I whipped the old one off in 2 mins.( no need for a ratchet spanner or pinching my fingers constantly)

    Wasnt in bad shape but for 20 quid I might as well put in a new one.

    Will post pics later.
     
  5. Buckhandle

    Buckhandle Active Member

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    Dear Matt,

    Thank you for sharing your experience with great documentation. This it not a problem to me yet - but I assume that my time will come :eek:)

    Lars
     
  6. Aidan88

    Aidan88 Active Member

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    Thanks for writing this up - I just forked over money to get mine done but now I know what to do next time!
     
  7. markespark

    markespark New Member

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    Hi - how much do you think im looking at paying to have this done ?
     
  8. Sidebar

    Sidebar Member

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    We are going to be repairing our td5's oil cooler in a campsite in Northern Chile. Trying to get parts organised from the UK.
    Which gaskets need to be replaced when repairing the oil cooler? Great write up by the way.
     
  9. Buckhandle

    Buckhandle Active Member

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    Hi Sidebar,

    As I see it, you just need the the two o'rings. But you should pm Mturri.

    Meanwhile I would strongly suggest that you also get new gaskets for the turbo and exhaust manifold. Even more important though you should get a couple of new bolts for the manifold in case they brake. The tend to do - and can be difficult to get out.

    Only because of the manifold bolts, I would actually prefer doing it close to a workshop. In worst case the may have the tools to get the broken bolts out.

    Have fun in Chile!!

    Br Lars
     
  10. eddyoz

    eddyoz Member

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    That allen headed plug between the exhaust ports looks like a potential water leak....worth replacing as well..part no LCM100170.
     
  11. jemj

    jemj Member

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    I wish I had known about this a couple of years ago. I replaced an engine thinking it had major problems but not until I had first done the head gasket and two top hoses. Still you are never too old to learn something new.
     
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