Water bubbling in expansion tank

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Anthracite
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MGF Register Region: North Wales
Model of Car: 2000 MGF 1.8mpi

Water bubbling in expansion tank

Post by Anthracite » Mon Feb 13, 2012 1:59 pm

Ive just done a Hgf change on my Mgf and now the coolant is bubbling and I am getting steam out the vents inside the car. I've done everything how I should, and spent ages bleeding the system. Also the fan does not appear to be working. I changed the fuse as it had blown but still nothing. Please help :)

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Dingbat
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MGF Register Region: Devon & Cornwall
Model of Car: MGTF 160 Sprint
Location: Near Sidmouth, Devon

Re: Water bubbling in expansion tank

Post by Dingbat » Mon Feb 13, 2012 5:31 pm

Hi, there.

Sounds like a leaking heater matrix to me.

A sound cooling/heating system operates under pressure and as a consequence the coolant does not "boil" despite running at higher than normal boiling temperature. The bubbling coolant is actually boiling away indicating that the system is not fully pressurised. The fans are not coming on because the temperature is not high enough to trigger the sensor.

So, the coolant system has a leak somewhere. The fact that you've got steam coming out of the internal vents suggests that the heater matrix is the culprit. Probably explains the presence of radweld type gunge as per your other post

Pig of a job I'm afraid - had to do it on my son's Peugot 306 not so long ago.

HTH

Brian
Brian Dingsdale
TF 160 Sprint, VHS Dampers, glass rear window, B&G low coolant alarm, Mud flaps, rear light protectors, Powdercoated and polybushed subframes (Royal Blue). Stainless coolant pipes. Braided brake hoses. Greasable clutch release arm.

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    Dingbat
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    Re: Water bubbling in expansion tank

    Post by Dingbat » Mon Feb 13, 2012 5:51 pm

    Sorry, Andy - it wasn't your earlier post it was one from "station", so please ignore my comment about radweld gunge.

    Old age catching up on me!

    Still sounds like the heater matrix though. How high does your coolant temp gauge get before the bubbling starts?

    Brian
    Brian Dingsdale
    TF 160 Sprint, VHS Dampers, glass rear window, B&G low coolant alarm, Mud flaps, rear light protectors, Powdercoated and polybushed subframes (Royal Blue). Stainless coolant pipes. Braided brake hoses. Greasable clutch release arm.

      Bandit
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      MGF Register Region: Cotswolds

      Re: Water bubbling in expansion tank

      Post by Bandit » Mon Feb 13, 2012 5:57 pm

      Unplugging the connection to the brown ECU coolant sensor should trigger the radiator fan, the ECU has a 'when in doubt run the fan' safeguard. So if that doesn't activate the fan, it may be dead - the fuse wouldn't blow in normal circumstances unless the inductive load is very high, i.e. either a partially seized fan motor (after long period of inactivity) or one that has officially gone to meet its maker.

      Bandit
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      Re: Water bubbling in expansion tank

      Post by Bandit » Mon Feb 13, 2012 6:09 pm

      It's possible there was some accumulated i.e condensated moisture on the heater matrix, it's that time of year, but if you're seeing a constant issue of steam from the vents then Brian's likely to be right. A matrix that has been watertight during normal use but then 'dries out' due to being drained down can result in any lining of deposits e.g. limescale hardening and cracking, revealing leaks that technically were there before but coolant wasn't actually escaping.

      Which of the 3 bleed points did/do you get most air out of? That can be a clue as to where the coolant is being replaced by air.

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      Anthracite
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      Re: Water bubbling in expansion tank

      Post by Anthracite » Mon Feb 13, 2012 7:16 pm

      Thanks for all the replies. I left the car cool, bled the system rad, heater then rear hose bleed plug and seems to have sorted the steam, fan and boiling :)

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      Dingbat
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      Re: Water bubbling in expansion tank

      Post by Dingbat » Mon Feb 13, 2012 8:17 pm

      Hi, Andy.

      Glad you've got it sorted - keep an eye on the levels and possibly invest in a low coolant alarm.

      Regards

      Brian
      Brian Dingsdale
      TF 160 Sprint, VHS Dampers, glass rear window, B&G low coolant alarm, Mud flaps, rear light protectors, Powdercoated and polybushed subframes (Royal Blue). Stainless coolant pipes. Braided brake hoses. Greasable clutch release arm.

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        Anthracite
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        MGF Register Region: North Wales
        Model of Car: 2000 MGF 1.8mpi

        Re: Water bubbling in expansion tank

        Post by Anthracite » Mon Feb 13, 2012 8:20 pm

        Did think about putting a low coolant alarm in, but the uprated gasket, water pump, cam belt, tensioner, uprated oil rail, stretch bolts and radiator have already hit my wallet hard. Not forgetting 2 new tyres. Im just gonna have to keep a close eye on my levels.

        SHAPESHIFTER
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        MGF Register Region: Elsewhere

        Unloved MGF by previous owner

        Post by SHAPESHIFTER » Wed Mar 15, 2017 2:04 am

        Hi,
        Only driven my 1996 MGF once, back from the dealer, broke down on the way home :( only travelled 140 miles from dealer ... taken to auto electricians by recovery, needed new regulator (starter brushes, alternator voltage - low)... only cost me $136 NZ Dollars for parts & freight ( 75 GB Pounds ) dealer had to pay labour $500 NZ Dollars ( 285 pounds ).
        Collected it yesterday :) wasn't far from home & noticed steam coming out the rear vents where expansion tank is, car smelt hot inside and temp wasn't far off the red mark .... slowed right down, got it home after a short distance ... waited for car to cool, checked water / coolant level .. shocked that it was empty ! filled expansion tank, checked and topped up oil, left it overnight, no leaks under the car, expansion still full, started car, watched gauge, stayed at the half way mark for a while then went to one mark below red ... radiator fan kicked in as could hear it at the front, couldn't hear engine fan, checked fuse no.6 in the front, it looks fine, can't locate fuses under steering wheel ( fuse no. 15 ) either well hidden or not looking properly ... Not sure if tank has air lock or the head gasket gone .... I am by no means a mechanic so only know the basics .... was hoping to book it in for a full service ( replacing all liquids ) and new cambelt, water pump & tensioner..... Grateful for any help, ( nervous about driving it the 38kms or 35 ish miles to my nearest garage )

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        RobboMC
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        Model of Car: 1999 Mpi

        Re: Water bubbling in expansion tank

        Post by RobboMC » Thu Mar 16, 2017 1:35 am

        Anthracite wrote:Thanks for all the replies. I left the car cool, bled the system rad, heater then rear hose bleed plug and seems to have sorted the steam, fan and boiling :)
        I bleed mine HOT. I know it's not recommended but dealers need to be covered by workers comp.

        Run system until thermostat is open, ( how do you know the thermostat is open??? well the radiator fan comes on! This can take quite a
        while, like 15 min if it's cold ) switch off engine. CAREFULLY remove filler cap,
        PUT ON DECENT RUBBER GLOVES, unclip coil wire if pre-2000, remove air duct to throttle body,
        then crack open the engine bleed screw with a 8 mm socket. Be careful not to drop the bleed plug like I did.

        You lose a lot more coolant this way but you know ALL the air is out.
        Also bleed and rebleed the heater and radiator bleeds when system is HOT.

        Make sure you start engine before replacing the cover. I know this is not the recommended method,
        and all advice given here is by amateurs like me, so take this info or not, up to you. I have done my car twice this way
        and a single hot bleed has worked fine.

        I suspect you may have left air under your thermostat when bleeding the engine bay. I also suspect that
        it's possible for these engines to idle happily with the thermostat shut if the heater if full on, especially in winter.

        This summer in Sydney it's been around 40 deg C for a string of days so I had no such problems
        when I did mine in January. LOL.

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        RobboMC
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        Re: Unloved MGF by previous owner

        Post by RobboMC » Thu Mar 16, 2017 1:40 am

        SHAPESHIFTER wrote:Hi,
        .. Not sure if tank has air lock or the head gasket gone ....
        Either way it should go back to the dealer. You can do a LOT more damage by driving these cars without coolant in them, trust me I have a thoroughly cooked engine in my garage that the previous owner killed.

        Personally I would get it towed and argue over the towing cost with the dealer.

        Read up on here about how the system should be bled and make sure they do it correctly.

        SHAPESHIFTER
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        Joined: Fri Mar 10, 2017 12:42 am
        MGF Register Region: Elsewhere

        Re: Water bubbling in expansion tank

        Post by SHAPESHIFTER » Thu Mar 16, 2017 11:15 am

        Dealer is approx. 250kms away, have a local dealer collecting it on his tow vehicle as I live rural ... he said he will bleed the system, check hoses are on securely as I had an auto electrician replacing the regulator last week ... and look at thermostat ... thanks for advice RobboMC :)

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