P505 GTI Coolant loss
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  1. #1
    Fellow Frogger!
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    P505 GTI Coolant loss

    My second topic.

    I have a series 2 P505 GTI ('86 leaded), which has only travelled 139,000 km. It has been de-registered for nearly 3 years, as I had the use of my daughters Renault Virage, and that seemed a good opportunity to trace a mysterious loss of coolant. I have only recently started to tackle this problem, due to other committments.

    The loss was initially only slight, with the low coolant light appearing after some 1000km. However, the situation slowly worsened to the point of obvious overpressurisation of the cooling system (rock hard top and bottom hoses), and the use of a litre + of coolant over 600 km. Further, slight bubbling appeared in the expansion bottle (cap released), and if the engine was allowed to idle (coolant caps in place) to the point of activating the thermatic fan, it would sometimes run irregularly (like a cylinder misfiring. Head gasket??

    There was no change in the engines performance or economy, no oil or water discolouration, nor overheating. Re-torquing the head did not assist. What was equally intriguing was the sustained pressure in the hoses, even a day or so after the engine had been switched off.

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    Other evidence was the loss of coolant (very slight)from the water pump housing. I thought that this may have been due to the very high system pressure.

    I have removed the head, had it crack checked, cleaned, a very light surface skim (despite Workshop Manual note), and the valves re-faced. There was no positive indication of any problems, and the liner projections were in limits. I am now reassembling the engine, with my fingers crossed. Anybody else experience a similar problem??

  2. #2
    Fellow Frogger!
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    Kim,

    Coolant Loss - this takes me back a few years to [perhaps] a similar problem that I had with a 1984 505 wagon - there the problem turned out to be the coolant level unit (screws into radiator). I have an idea that a fine crack in the plastic (or
    something like that) allowed a small amount of coolant to escape that was barely noticeable. Other points to check - does your 505 have the electrically operated control valve for the heater (mounted in engine bay RHS below brake booster). This could give you problems with leakage and coolant loss.

    On re-reading your post, you can almost certainly disregard my comments above. Given that the system has become pressurised as you say, yet not overheated, the only thing that makes any sense (to me) would be a head gasket leak. It could
    be a major blockage in the radiator but that wouldn't fit with the pressure remaining in the system overnight. It must have been an interesting leak that would open when the engine was up to temperature and then 'reseal' when the engine cooled down - otherwise the pressure would leave the radiator system as coolant entered the engine oil.

    Many years ago my sister had a 404 that blew a head gasket. It took many weeks before the problem 'really' developed - initially there was coolant loss, finally you could see a little steam in the exhaust and ultimately the leak was sufficient to cause the engine to overheat in ten minutes [and at this stage the oil became emulsified]. So hopefully you've found the problem.

    Once a head gasket of the thermo-setting type starts to leak any retightening of head bolts won't make any difference.

    Finally - head shaving - normally not needed. Once I corrected a warp in a 504 cylinder head by scraping it flat. All you need is a piece of float glass (say about 10 mm thick - from any decent glazier) which you then use as a surface table in reverse with some Reckitts blue to find the high spots. Use an engineer's scraper. The whole process took a couple of hours. I guess it
    should go without saying that if you remove the cylinder head and are not renewing the liner seals, you should not rotate the engine under any circumstances. If you do you could move a liner or two in the engine block which could allow some dirt into the space for the liner seal. In this case the liner may not seat properly in the block and could leak coolant. An exception would be if you used a couple of flat bars, with say the cylinder head bolts and some spacers to lock the liners in place.

    Also, both the head, block and liner protrusion may be easily checked with a 600 mm straight edge (engineers rule) and a set of feeler gauges. Check, cross check, turn ruler over and end to end etc.

    Well these are a few comments.

    cheers

    Denis

    [ 15 February 2002: Message edited by: Denis ]</p>

  3. #3
    1000+ Posts Rod Hagen's Avatar
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    I find myself wondering whether the pressure release in the radiator cap is operating , or whether the line to the expansion bottle is blocked.

    This would cause the extra pressure in the system and the slight loss of coollant through the water pump.

    If you continue to use the vehicle with the system over-pressured, water pump and head gasket failure are likely possibilities.

    The other possibility , of course, is a gas leak from the combustion chambers into the cooling system due to a problematic head gasket or cracked head.

    I would fear the latter (though your work on the engine should now have fixed it) , but normally the first would be worth eliminating before you go down the head or head gasket replacement route.

    One other possibility might be "cavitation" of the waterpump caused by either air ingress at the pump, or a poor gasket seal between the inlet and outlet sides.
    Cheers

    Rod

    [ 15 February 2002: Message edited by: Rod Hagen ]

    [ 15 February 2002: Message edited by: Rod Hagen ]</p>
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  4. #4
    Moderator Alan S's Avatar
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    Kim,

    I'd be inclined to blame the liner seals. I had a similar problem many years ago with a Renault which was doing similar strange things.
    I know it's a #$%^ of a job to have to replace them but by the same token, think what's involved if you do the head over and THEN have to do these things; lots of double work.
    With froggymobiles it is always important that the cooling system is always bled thoroughly although given your symptoms I don't believe this is your problem this time around.
    The guy I bought my Citroen BX 16 valver off in Sydney had the liner seals go on his own 16V just after I bought mine as I was interested in grabbing his also but he jacked the price through the roof after this little episode (a dealer charged him $4500 to repair it) and after seeing the insides of my cooling system, I believe the cause was incorrect coolant.
    Hope this is some help

    Alan S
    If it ain't broke, use a 12" shifter.....that usually does the trick!!

  5. #5
    Fellow Frogger!
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    Some thoughts on the replies.

    As mentioned, I did check the liner protrusions, and they seemed to be according to specifications.

    The question of a fine crack in the head is also hopefully eliminated, as that was checked at the time of the surface clean and valve re-face.

    The coolant expansion bottle cap always remained a possibility in my mind, if only because, if I drove the car with the cap loosened, the symptoms were minimal (unless I continued to use an actual coolant!) Strangely, the use of straight water minimised the extent of the actual coolant loss.

    The water pump is being replaced (along with all front oil seals, cam belt and tensioner etc. And yes, as an owner and maintainer of wet sleeve engined cars (Renault & Peugeot) for 35+ years, I can confirm that I used liner retainer clamps.

    Thanks to all who have replied so far.

    Kim.

  6. #6
    Fellow Frogger!
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    [quote]Originally posted by Kim Slattery:
    <strong>Some thoughts on the replies.

    The coolant expansion bottle cap always remained a possibility in my mind, if only because, if I drove the car with the cap loosened, the symptoms were minimal (unless I continued to use an actual coolant!) Strangely, the use of straight water minimised the extent of the actual coolant loss.
    </strong><hr></blockquote>

    For diagnosing faults, one 'trick' that I have used is to slowly release the expansion bottle cap when the engine is hot. The coolant should just expand into the bottle .. and any sign of gas or bubbles is an indication of head gasket problems.

    I guess by now though you won't be able to try this 'test' because the engine is stripped down.

    However, from the repairs you will complete I think you will overcome the coolant loss problem.

    Denis

  7. #7
    Fellow Frogger!
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    Thanks to all who contributed. I will be away on business in Spain from today (Sunday)until the 27th MARCH. Will keep the Forum advised after that date.

    Kim.

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