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Thread: Head Gasket or Thermostat

  
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    Head Gasket or Thermostat

    hi, i have a mk4 1.6 8v astra and have recently discovered a beige coloured sludge under the oil cap. my girlfriends mum's bf is a mechanic and reckons my car will be fine, he smelt the coolant to see if he could smell petrol. not quite sure why you would smell petrol as oil doesn't smell but yeah.

    i have a few schools of thought so would appreciate all opinions:

    CONDENSATION

    coolant level hasn't dramatically dropped and the sludge is only around the top of the oil cap and tip of oil dip stick, so could possibly be due to the cold weather and the fact i go on short journeys means engine not getting hot enough for vapor to evaporate.

    HEAD GASKET

    sludge is a sure sign of head gasket on its way, so mine could be too however i haven't lot any power, coolant hasn't really dropped and around the gasket look fine. plus the head went in 2007 before i bought the car, so its a relatively new HG.

    THERMOSTAT

    this is my dads opinion, he reckons the thermostat is stuck open hence the condensation. he checked the coolant pipes for leakages, checked around the HG, and looked in the breather pipes, which were completely covered in sludge. my dad thinks its the stat stuck open because it doesn't matter how long i run the car my temp gauge doesn't move at all, I'm always complaining about my crappy mpg, and my car is very punchy for a 1.6 8V. my dad said my car is probably running cold hence getting the condensation sludge and low temp gauge readings.

    Sorry for the long essay, all comments appreciated as im completely unsure what it is.

    although my dad said the thermostat is a big job to get to in these engines so might be better to add a second stat further in the pipe before the radiator.

    Thanks for taking the time to read this, just looking at it make me think omg lol
    sorry if i write my christmas letters to satan, im dyslexic.

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    It seems to be a trait with the 8v engines...

    Mainly due to short journeys - remedy is to do more frequent oil changes.

    ....or use the car more


    PS . stick your nose in oil - it does smell !

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    cheers I'm hoping the second stat will sort the problem, dad did mention flushing through the oil a few time with cheapy oil before putting in my regular castrol.

    oh and thanks for the advice i almost drowned sniffing up oil, very bad idea lol
    sorry if i write my christmas letters to satan, im dyslexic.

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    i had the same problem with my old Astra mrk3 cause it never went more than 20 miles a day..

    easyest fix was oil flush with shity asda chepo oil, away a long drive, then do a flush then another drive then proper oil, and just make sure you do good drives now and then.. as coo said.. the 8v cars seem to suffer this allot
    The coupe...ITS ALIVE & back from the dead....again!
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    yeah i dont think i do more than 20miles a day will defo flush the oil through tho. what due think about the second thermostat idea? i read on other forums and it seems to work, spose its worth a try.
    sorry if i write my christmas letters to satan, im dyslexic.

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    no sure on that part buddy.. i aint got a clue about thermostats ata ll..

    all i would say is if tyhe car heaters aint working that usually points to the thermo, but if its gammed on all the time then i have no idea really sorry LOL
    The coupe...ITS ALIVE & back from the dead....again!
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    thats kl cheers, heaters work fine, infact once they warmed up it starts to burn me lol cant have them on too long even tho it takes 10mins driving for them to get going.
    sorry if i write my christmas letters to satan, im dyslexic.

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    Hey,

    I had a very similar problem - car was running cold and there was sludge. Since your temp sensor is dead (exactly what was happening to me) then this is your thermostat stuck open. Could be worse... could be stuck shut, and your engine would overheat pronto. However, with your poor MPG and the sludge and the new gasket and the fact that you engine never gets up to 95C... I reckon its your thermostat. Its a remarkably common problem.

    The stats can be very awkward to replace though. I have an MKIII from 1997 and the stat housing is directly behind the cover for the timing belt. With two people and a decent sized nylon zip tie you can get one guy to hold the whole arrangement forward and keep the belt attached while you switch out the stat. I did this recently and it took about an hour for the whole job start to finish, about 10 minutes to actually pop the old thermostat out and put a new one in. If you have easier access on your engine then it will be much faster to change.

    Don't forget to get a new sealing ring with the new stat! Very important. Also, buy the stat new... no point in risking a sticky second hand stat when they only cost about a tenner new. Go to a dealer, I bought a new stat from an Opel dealer for 8 euros (I'm in Holland right now... long story).

    Try this to fully diagnose:


    • Turn your engine on
    • Turn your fan and heater on full
    • Lock your car, leave it where you can see it
    • Go get a cup of coffee
    • Come back in 30 minutes... has the sensor moved?


    If its not, and its still resolutely in the blue, then you may have a dody sensor too, but most likely your car will be at around 90C, maybe higher. Then, take it for a drive and watch it drop right back down in less than five minutes, faster if you take it on the motorway or go fast. If this happens then your stat is stuck open.

    If its still cold after 30 minutes idle thencheck your sensor. Its an easy job to do and all you need is a thermometer, some spare collant and a multimeter. I can PM you the resistances you should be reading at certain temps if you want, I've still got them laying around.

    ... hope this helps!

    Forgot to mention: if you replace your stat you will see significant improved MPG immediately and your sludge will eventually just sort itself out, mine did.

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    coffee? think ild rather have a tea lol. yeah could you please pm me the resistances please i havent got a thermometer or multimeter but will defo be able to get hold of them.

    Didnt think of the sensor, the needle on the gauge dosent move at all, i sat in traffic for almost an hour tuesday and the needle stayed cold, didnt really acknowledge a problem but now u mention it, got me thinking.

    Thank you so much for this help. T
    sorry if i write my christmas letters to satan, im dyslexic.

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    yeah my dads 2.0 bm get better mpg than my 1.6, im guessing its near 18mpg which is killing my wallet lol
    sorry if i write my christmas letters to satan, im dyslexic.

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