DPO Auto Heat Exchanger – coolant hoses.
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Thread: DPO Auto Heat Exchanger – coolant hoses.

  1. #1
    1000+ Posts Fordman's Avatar
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    Default DPO Auto Heat Exchanger – coolant hoses.

    I have been looking at improving the cooling of the ATF as our Scenic is driving quite ok until it gets quite hot, then it has issues of shuddering and sometimes no drive at all. Thanks to info on this forum, I find I can purchase a 25% larger oil cooler (heat exchanger) – genuine Renault from a later model – and I have been tossing up between this, and a separate air/oil cooler.
    Just another DPO day.
    Now looking at the actual hose layout of the Scenic (built 2003), it has what I consider to be a strange layout, and wonder if the coolant flow through the cooler is adequate. Not doubting for one moment that the Renault engineers know what they are doing, but I have a question I hope to get an answer for.
    The question is – does the lower radiator hose have a built in restrictor to force the coolant to flow through the auto trans cooler? As the cooler is in a bypass situation, which I would think is not a positive method of coolant flow – unless maybe the main flow is restricted.

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    Any opinions, or even someone with actual knowledge of the restrictor?
    BTW, the lower rad hose is like an octopus, with moulded connecting hoses to both the trans cooler and the cabin heater – it would be worth a pretty penny, I reckon.
    Also any opinions/actual experience with an air/oil cooler on a DPO/AL4 trans?

    Pic 01 – copy of relevant coolant circuit from Haynes manual. Note trans cooler input and output both from lower rad hose, so why would any coolant flow? Or does it get enough flow to efficiently cool the auto fluid? My guess is there has to be a restrictor in the lower hose between the two cooler hoses. BTW, item 6 in the diagram is a restrictor in the bleed hose from thermostat housing to coolant recservoir.

    Pic 02 – Actual photo of relevant area. Note there is a stainless steel strip around the lower hose, could this be holding the restrictor, if indeed one exists? (Front of car is towards bottom of this pic).

    Pic 03 – there’s the cooler, hiding down there at the upper rear of the transmission, just for info. (Front of car is to the right of this pic).

    Attached Thumbnails
    Hose Layout 01.jpg Hose Layout 02.jpg Hose Layout 03.jpg
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  2. #2
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    Line 5 in above post should be the link to previous thread, with relevant history.

    Just another DPO day.

    Can't seem to edit my posts these days.

    Cheers.
    2004 Scenic I 2.0 auto (Hers)
    2016 Ford Territory (His)
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    Hi Fordman
    It is hard to see the logic of that cooling system, as far as the transmission goes . Perhaps it is designed to warm up the transmission during very cold weather rather than address the hot weather. Having a restrictor in that bottom hose does not make sense either.

    Perhaps an air cooler is a better understood method to pursue. Tried and proven ! Even if fittings are not a available off the shelf.
    Here is the NSW Citroen car club mag with an article about transmission coolers and adaptors. Do'nt tell anyone I gave it to you
    https://gallery.mailchimp.com/67a389...9_03_Email.pdf
    jaahn
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    Quote Originally Posted by jaahn View Post
    Perhaps an air cooler is a better understood method to pursue. Tried and proven ! Even if fittings are not a available off the shelf.
    jaahn
    Thanks, Jaahn. The good news is that an adaptor for the AL4/DPO for an air/oil cooler is readily available at a reasonable cost. Adding the cooler and hoses, plus a fair bit of fiddling around, the 40mm heat exchanger is probably cheaper, but I agree the air/oil may be the way to go.
    Interesting flow system, isn't it?
    2004 Scenic I 2.0 auto (Hers)
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    When I was researching the external cooler option the AL4 adapter was not so easy to obtain any longer. I think I tracked one down at Alltranz jn Sydney but was like $250 plus the pipes and radiator.
    Not had the heating issue since box built and new heat exchanger installed.

    Still have Red Devil to replace heat exchanger as its terrible in heavy traffic

    Will be interesting to see how you get along.

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    Shouldn't cost that much. It cost me $125 all up in admittedly 2005 for an air oil cooler, hoses and adaptor (i made up myself, just horizontal drilling of 2 bolts and 2 banjo fittings). It was for an AD4 set up in a R19
    The DPO cooler might be differently configured? The insides would be similar and over time they gunk up, i'm pretty sure about that.
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    Quote Originally Posted by JoBo View Post
    Shouldn't cost that much. It cost me $125 all up in admittedly 2005 for an air oil cooler, hoses and adaptor (i made up myself, just horizontal drilling of 2 bolts and 2 banjo fittings). It was for an AD4 set up in a R19
    The DPO cooler might be differently configured? The insides would be similar and over time they gunk up, i'm pretty sure about that.
    Wow, your A4 heat exchanger was certainly past its due by date, as far as clogging up is concerned. I think my cooling system is in fairly good nick, but even a small amount of crud deposited in the fine tubes would be reducing the cooling effect measurably.
    Approx how old was the R19 at that stage?

    The DPO adaptor is probably harder to make, but if I had access to a decent lathe it would be OK, they need to have a flat surface with a recess and O-ring groove machined in about the diameter of an oil filter O-ring. Nice looking alloy one available in Aust at ridiculous $350.
    Others available on ebay from various dodgy looking countries.

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  8. #8
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    Default New 40mm heat exchanger

    OK, after thinking about this for a few weeks, I have decided to go the route of the 40mm heat exchanger, giving me approx 25% better cooling than the standard 30mm one on the car, plus any extra efficiency gained with a new unit over a possibly crud-filled original, hopefully not as bad as JoBo's R19 cooler. In my experience, cooling systems are designed pretty close to the limit, for the good reason of not over-cooling the engine coolant, so a 25% increase may be just enough to extend the driveability of the auto trans to be a reasonable shopping car. Took it out the other day, after 20kms on a 28°C day, it was almost neutralising from rest, and clunking down on stopping, cooled down for an hour, drove perfectly home.

    Yes, I know I'm only covering a hard defect in the auto, but it does seem to be much heat-related, and I'm not prepared to spend thousands on the auto when there are no fault codes to indicate what the problem is, and the car drives ok up to that point. When the time is right, I may do something more to actually fix the defect, but having the better cooler re-fitted then will only help its longevity.

    And this is actually the cheapest, easily available, and easiest to fit option. The air/oil cooler I expect would be the best to really cool the trans oil, but purchasing the adaptor plus cooler and fan would be about $500 plus a lot of fitting work, maybe installing a temp switch as well.

    For a laugh, I did also come up with a bit of an alternative, leaving the existing cooler in position, and running a small radiator (heater core) in series in the coolant hose just before the auto cooler, basically adding another air cooler into the equation, maybe even as a separate circuit with a small 12v electric pump circulating the coolant just through the auto heat exchanger. Hmmm. Parts available but got a bit expensive, just a bit of a lateral diversion. Would save me having to remove the auto cooler, losing the ATF etc, but what if it was blocked, I would need a new cooler anyway.

    Thanks to dimistyle making me aware of the larger cooler. The part number is listed in Renault Australia but not available and listed at over $600! It is possibly standard equipment on a later/different model. Anyway, against my normal practice, I ordered one on-line from UK, it is the genuine Renault product, it took just 4 days delivery from UK (!!!!) and the cooler, longer banjo bolt and freight total was A$210!!!

    The first thing I noted was it is quite heavy, weighs just over 1kg, unusual for modern car parts I thought, but looking inside it appears to be a bronze-looking matrix, with many plates, so quite solid, hopefully good for longevity.

    40mm Cooler 01_red.jpg40mm Cooler 02_red.jpg40mm Cooler 03 (2)_red.jpg

    Will advise when fitted and results, or disappointments!

    Cheers.
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    Looks nice and worth it weight.
    I found one locally so never ordered from overseas. But never had a heat related problem buyt I rebuilt the gearbox at the same time.


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    Quote Originally Posted by Fordman View Post
    Wow, your A4 heat exchanger was certainly past its due by date, as far as clogging up is concerned. I think my cooling system is in fairly good nick, but even a small amount of crud deposited in the fine tubes would be reducing the cooling effect measurably.
    Approx how old was the R19 at that stage?

    The DPO adaptor is probably harder to make, but if I had access to a decent lathe it would be OK, they need to have a flat surface with a recess and O-ring groove machined in about the diameter of an oil filter O-ring. Nice looking alloy one available in Aust at ridiculous $350.
    Others available on ebay from various dodgy looking countries.

    About 12 to 15 years. Neglected cooling system by previous owner.
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    Hi Fordman
    Sounds like you have a workable plan. The budget always has a bearing on our moves.
    Another thought I have had would be to put a fan blowing directly on the end of the gearbox. It has a largish area of mainly alloy with the oil splashing around the inside. So introducing some cooler outside air, from the wheel area, would provide some welcome cooling. Particularly compared to the hot air that is coming in through the radiator currently in hot weather.
    Just a thought !
    Jaahn
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  12. #12
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    Replaced the auto trans heat exchanger (cooler) with the new 40mm cooler last week, as I needed the extra car for the weekend.

    The good news is that we did nearly 300kms over the weekend, running around outer urban areas, in approx 25-28°C ambients. Mostly trips were about 22 kms on main roads, one trip 60 kms continuous in hottest part of day. Other than the usual slight shudder into 2nd and 4th, the transmission did not feel too bad at all, with no major shudders or loss of drive. Previous test drives a few weeks ago had loss of drive after 15-20kms in similar ambients. Fingers are crossed that it doesn't have a major relapse, as it seems fairly normal now.

    To keep the job simple, I clamped the coolant hoses to the cooler instead of draining the system. Had to go out and buy a 30mm ring/open end spanner (Bunnings $23), and reaching the banjo bolt was quite difficult, but got the job done. Before installing the new cooler, I filled it with Penrite FS on the bench, then poured it into a measuring cylinder (cooler held 75ml), estimated the recess in the transmission which had emptied on removal of the old cooler at approx 50-75mm, so just topped up the trans with 150mls after cooler fitted. I had recently changed the ATF to Penrite FS, and had carefully got the level correct, so I know I am still pretty close. Topped up coolant, and checked for leaks after running for a while - all good.

    The old cooler was not visibly blocked at all - it looks as clean as the new one in the coolant side. This means I am probably not gaining anything because it was partly blocked, but am happy with that. I must say, its a feather in the cap for the genuine Renault Type D Coolant which I have been recommending since seeing how clean the engine block was when I changed the water pump at 7 years old. Its due again (well overdue) but the coolant is still clear, clean and green. It will be changed asap.

    So hopefully the 25% extra cooling to the trans fluid is just enough to prevent the previous heat-related problems. I acknowledge that it isn't repairing the actual fault, whatever that might be, as there are no fault codes, and the next stage would have to be further internal work, probably a complete overhaul. The 2 main solenoids were replaced about 10k kms ago, if that.

    I also have no idea what temp the trans fluid is actually reaching, no warnings have been observed, but I don't know if the system would give me a warning anyway.

    So I'm calling it a successful stop gap repair, the car is quite driveable now, and let's see what happens next summer!

    Cheers.
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  13. #13
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    This is great news to hear on the DPO/ AL4 front.
    When transmission fluid hits 100 degree you will lose a few gears and car will be very sluggish the only way I know this by monitoring the Auto with Lexia and noticed the when fluid was 100 or over it never change gears properly

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  14. #14
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    Quote Originally Posted by dimistyle View Post
    This is great news to hear on the DPO/ AL4 front.
    When transmission fluid hits 100 degree you will lose a few gears and car will be very sluggish the only way I know this by monitoring the Auto with Lexia and noticed the when fluid was 100 or over it never change gears properly
    That is very helpful info for the future, and may explain what I thought was happening.
    Thanks.
    2004 Scenic I 2.0 auto (Hers)
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