306 losing coolant
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Thread: 306 losing coolant

  1. #1
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    Default 306 losing coolant

    Happy new years chaps

    My GTi6 appears to be chucking out coolant. The level always seems to drop a bit after a service, then levels out and stays put. Quite possibly a contributing factor is that the driveway at mum's place is on a fair angle, and where I normally park when visiting would tilt the coolant towards the radiator cap. I get the feeling that it's been venting the 'excess' coolant when visiting on a hot day, leaving it low when the car is level again.

    Anyhoo I normally keep an extra eye on it during the warmer months, and when it was 40C on Dec 31st I noticed it had left a small puddle below the overflow pipe after a drive. When I checked the coolant later that day it was pretty low, probably a good 6" below the radiator cap. I've topped it off with demineralized water today (took about 1.5l), but before that I let the engine get up to temp with the radiator cap off so I could look for any bubbles, just in case. I did see a tiny bit of bubbling, but it only happened when I backed off the throttle...not sure if that's normal or not. Neither coolant or oil look contaminated, engine not blowing smoke and runs perfectly (albeit a touch warm during summer). After topping up I tried the same test and couldn't see any bubbles at all, but I'm going to do it again this afternoon just to be extra sure.

    Radiator is an aftermarket Nissens unit btw, this one. Only a year or so old. No overflow tank but I think I could probably squeeze a small bottle in behind the headlight so I can more accurately track how much & when it decides to spit out coolant.

    Any advice and/or thoughts appreciated

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    2000 306 GTi6 'Josie'

  2. #2
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    Only generic advice from me as I don't know the 306. Anyhow 6" means a lot of missing coolant.

    For starters, perhaps there's no real problem. Some systems really don't like the radiator cap removed because it introduces air between radiator and overflow tank and it can take a couple of drives to purge that air. Yours doesn't have an overflow tank, so I guess that's not it. It'd probably be a good idea to fit one simply because it gives you so much more cooling capacity. Without a tank you shouldn't fill to more than about 1.5" from the cap.

    Is there a lot of air hanging around at the top of the engine -- does it need bleeding?

    What do you mean by bubbles? When you back off from a rev, a surge is normal (the water pump slows down immediately, the water keeps going at the previous rate and backs up in the top tank of the radiator). But if you're seeing small bubbles, that could be a blown head gasket. Tests described in the nearby thermostat vs. water pump thread.

    Finally, if coolant is getting past the radiator cap purely because of angle, something's wrong. Wrong or damaged cap, damaged seat where it should seal on the radiator, etc. If your cap isn't sealing it'd be pretty easy to drop the water level 6" with surge. So that'd be my first port of call.

    Have fun,

    Rob.
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    The bubbles initially were quite small, but I don't know, perhaps it was just the coolant being agitated by the waterfall of incoming fluid, given the low level (wishful thinking I know).

    Yesterday afternoon I did the same test (after the top up) and it was bubbling quite a bit more, but it looked more like water boiling agitation rather than air bubbles flowing through it. It would start doing it maybe 1-2sec after opening the throttle up, and continue for about 1sec after closing it.

    The radiator cap is certainly something I've considered. It does seal and hold pressure as you can hear the seal break when removing it, but whether it's holding enough pressure is unknown.

    I'm going to see about having the coolant tested for exhaust contamination ASAP and go from there.
    2000 306 GTi6 'Josie'

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    Those bubbles don't sound good, but if there was that much coming through compression leaks (gasket or crack) I'd expect a 4 cylinder to have noticeable symptoms: rough idle, low power and probably overheating.

    I had a Google around and the 306 does have cooling system bleed points (radiator, thermostat housing and head apparently). More importantly, they say these points are all above the radiator cap. You're running without an overflow bottle so your water level is even further down. Sounds like a recipe for chronic aeration problems.

    Finally, the trickle at your mum's place remains suspicious. Wherever you get the coolant checked for contamination, ask them to pressure test the radiator cap (might as well test the system too while they're at it.) They should have the necessary gadget.

    Have fun,

    Rob.

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    Need to trace the external leak in the driveway
    Could be water pump leak, ok when under pressure, leaks through seal when cold

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    Quote Originally Posted by robs View Post
    Those bubbles don't sound good, but if there was that much coming through compression leaks (gasket or crack) I'd expect a 4 cylinder to have noticeable symptoms: rough idle, low power and probably overheating.
    Same here, but the engine has been running without issue

    I've just had the system tested and they said the movement in the coolant is normal flow, and the contaminant test came back fine. Compression was a different story, he said the cap wasn't sealing tightly enough, in fact he seemed surprised it was even in one piece. I stopped by a Peugeot stealership afterwards and picked up a new OEM one.

    Quote Originally Posted by driven View Post
    Need to trace the external leak in the driveway
    Could be water pump leak, ok when under pressure, leaks through seal when cold
    I'm 95% sure the overflow pipe was the escape method, as the tip was usually wet when I checked it. I'll keep an eye out of course, but hopefully the new cap solves the issue.
    2000 306 GTi6 'Josie'

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    Quote Originally Posted by TrinityJayOne View Post

    ... the cap wasn't sealing tightly enough, in fact he seemed surprised it was even in one piece. I stopped by a Peugeot stealership afterwards and picked up a new OEM one.



    I'm 95% sure the overflow pipe was the escape method, as the tip was usually wet when I checked it. I'll keep an eye out of course, but hopefully the new cap solves the issue.
    Had the same problem with a 505 - the coolant loss was perplexing me. And then a Pug mechanic suggested the cap - problem solved! :-) Sometimes the problems DO have simple solutions.

    Ian.
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    Quote Originally Posted by TrinityJayOne View Post
    I stopped by a Peugeot stealership afterwards and picked up a new OEM one.
    Glad to hear that the cap is the likely culprit.

    Are you sure the Peugeot cap is right? You said it was an aftermarket radiator, perhaps it needs an aftermarket cap??

    You should consider an overflow bottle of some sort too. If the engine really sits higher than the radiator and the radiator has a permanent pocket of air at its top, that air's going to tend to migrate into the engine.

    Have fun,

    Rob.

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    Aftermarket OEM replacement, yes. I had similar thoughts but can't find any specs online. Nissens ship their radiators with all the parts included so there aren't any listings for radiator caps that I can find, and their parts catalogue is hidden behind a business customer login. I've sent them an email asking about it.
    2000 306 GTi6 'Josie'

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    No response from Nissens as yet, but I emailed RockAuto this morning and got a reply back. They reckon that because it's intended as a direct replacement the radiator shouldn't have any issue handling the same pressures as the OEM radiator. Seems like a fair call to me.

    At any rate the leak has stopped and the overflow pipe is dry. On closer inspection I'm not sure there's any room to cram in an overflow tank, at least not a real one. Might be able to wedge one of those small pop-top juice bottles in somewhere!
    2000 306 GTi6 'Josie'

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    Quote Originally Posted by TrinityJayOne View Post
    Happy new years chaps

    My GTi6 appears to be chucking out coolant. The level always seems to drop a bit after a service, then levels out and stays put. Quite possibly a contributing factor is that the driveway at mum's place is on a fair angle, and where I normally park when visiting would tilt the coolant towards the radiator cap. I get the feeling that it's been venting the 'excess' coolant when visiting on a hot day, leaving it low when the car is level again.

    Anyhoo I normally keep an extra eye on it during the warmer months, and when it was 40C on Dec 31st I noticed it had left a small puddle below the overflow pipe after a drive. When I checked the coolant later that day it was pretty low, probably a good 6" below the radiator cap. I've topped it off with demineralized water today (took about 1.5l), but before that I let the engine get up to temp with the radiator cap off so I could look for any bubbles, just in case. I did see a tiny bit of bubbling, but it only happened when I backed off the throttle...not sure if that's normal or not. Neither coolant or oil look contaminated, engine not blowing smoke and runs perfectly (albeit a touch warm during summer). After topping up I tried the same test and couldn't see any bubbles at all, but I'm going to do it again this afternoon just to be extra sure.

    Radiator is an aftermarket Nissens unit btw, this one. Only a year or so old. No overflow tank but I think I could probably squeeze a small bottle in behind the headlight so I can more accurately track how much & when it decides to spit out coolant.

    Any advice and/or thoughts appreciated
    Have you replaced the thermostat ? They are at the age when replacement is overdue!
    If a worn out (stuck open thermostat) is not holding the pressure it may lift the radiator cap expelling coolant
    A cheap elimination !

    Alain

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