1.8T seems to be overheating for no real reason...

Discussion in '1.8 & 1.8T' started by HidRo, Sep 2, 2017.

  1. HidRo Forum Member

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    So, we identified this when on the last trackday, it went up to 120C of water and light started blinking.
    I was hammering it of course, and we thought it could be the radiator was too small (smallest for the mk2 Golf). Changed it to the biggest for mk2's.
    Changed radiator, and cut the thermostat so it was flow through.
    Flushed the system, changed waterpump and belt (it was due) and tested it again.
    At idle, it will keep on raising temp, even with the fan working (Mishimoto slim).
    Fan kicks in at 87C, but temp will go high as 100+ at idle. Never goes down.

    Could the thermostat elimination made it climb like that? Or can there be any other issues?
    Also, we CO2 checked to see if the headgasket was bad, and it isn't...

    Any tips?
     
  2. rubjonny

    rubjonny Administrator Staff Member Admin

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    what did you do for the dash coolant sensor, as the mk4 one doesnt work correctly with the mk2 clocks. is the mfa oil temp working? another thing you can do is read the ecu measuring block for the coolant temp to make sure the dash is reading correct.

    how is the fan mounted as well, if its just strapped to the rad it wont work very efficiently as it can only cool a small section of the rad core. you could add another fan or build a shroud for it to force it to pull it thru the entire rad
     
  3. HidRo Forum Member

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    The sensor is the one for the ABA, as it will provide good readings for the ECU (Megasquirt) and also, will be OK for the mk3 clocks.
    The MFA oil is reading as well.

    The fan is mounted on the radiator, just strapped there. No shroud. I'm thinking of putting another next to it, doubling the cooling (1 takes half of the radiator).
    Not sure why it started to raise the temps, but after reading on another forum about the possibility to have air locks, it makes some sense.
    The water reservoir is connected to the slim black pipe, underneath the coolant flange where the sensor goes, etc.
    I have no heater, so the air might be trapped on the top of the engine (let's put it this way). I will do something to try to take the air out from there (if there is any).
     
  4. rubjonny

    rubjonny Administrator Staff Member Admin

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    yeah the mk3 one should be fine, I think you're probably right by the sounds of it theres an air leak
     
  5. HidRo Forum Member

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    So, we changed some of the pipes etc getting it the same way as the original diagram.
    Changed t-stat.

    Temp Sensor is good
    Fan switch is good.

    Car is still overheating. While driving, it's now running at around 80c(176f) (82C(180f) is the t-stat opening) and all good there.
    If I stop and let the car idle, the temp will go up to 105C+(220f).
    Fan will kick in when it's supposed to, but will never stop.
    Can't get why this is happening, and I'm running out of ideas...
    This didn't happen before. Trackday is at the end of the month, and this is not looking good :(
     
  6. rubjonny

    rubjonny Administrator Staff Member Admin

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    if the temps are fine while its driving around, then your radiator & stat are fine. it sounds to me like your fan isnt big enough and/or cannot work efficiently due to the lack of shrouding
     
  7. HidRo Forum Member

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    I had another fan, without shroud and it never ever did this up until recently. Then changed fan, still without shroud, and it's the same. We will put both fans there to see if it works better. Can a relay output less amps and make the fan slower?

    Sent from my Redmi Pro using Tapatalk
     
  8. rubjonny

    rubjonny Administrator Staff Member Admin

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    I suppose if the relay was starting to fail it could do that, I know when my fuel relay went bad it could only supply enough power to run the lift pump at times
     
  9. Nige

    Nige Paid Member Paid Member

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    What about oil temps? What are they showing?

    If your oil is getting hot, that will transfer to the water.
     
  10. HidRo Forum Member

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    At the time I tested this last night, I was able to see the oil temp in MFA, and it was showing 72c. I assume that is not that bad.
     
  11. shane d Forum Member

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    Is there any possibility that the fan is running the wrong direction?
     
  12. Nige

    Nige Paid Member Paid Member

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    Cutting middle out of the thermostat will keep it cooler.

    Have you recently changed ANYTHING. eg, Oil type / viscosity? Spark plugs?

    Basically, look for anything at all that you've changed, however unlikely it seems.


    Check the timing belt hasn't slipped, that could possibly be a cause.
     
  13. HidRo Forum Member

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    Shane, it is working in the correct way, sending air from the radiator to the engine.

    Nige, I changed to another type of oil, but recently. It overheated on the track before that, so oil is out of the equation.
    Sparks are the same. Maybe I'll change for new ones, but they are BKR7E's
    We changed the timing belt when we did the water pump, and it's spot on. Also, it overheated before changing belt.
    Would a slipped belt overheat on idle? It does run fine and cool when driving.
    Without the center piece of the t-stat it is too cold. It will go for ~60C. Well, maybe while driving on the track, it might get to a good temp.
    The only thing we changed that would be something to notice was the water reservoir location. It went from one side to the other (it's not at the stock MK2 location).
    We saw that the black thin pipe was changed in a way that could impact this (not allowing proper circulation) and we changed it back to making it circulate correctly.
    It's the same...

    The car pulls strong, even at 0.7/0.8bar so I THINK I might not have bent valves or something that could cause everything to run extra hot.
    I can't think of anything else to try :(
     
    Last edited: Sep 12, 2017
  14. Nige

    Nige Paid Member Paid Member

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    Ok, was worth asking.

    So, just to clarify. It is fine when on circuit and ONLY overheats when stationary and this started suddenly before you changed anything, apart from the location of the header tank?

    If the header tank is lower than before, that would make an airlock much more likely. Personally, I'd temporarily refit the header tank back where it was, just to discount that as the cause.
     
  15. HidRo Forum Member

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    It overheated on track. That is what lead us to do all the work we are currently doing.
    Not, as I'm preparing to go on track again, I was not able to test pushing it hard enough to see if it overheats while driving as on track.
    At the moment, driving at cruising speed of 120km/h with the t-stat cut, it will drive at 60C+. With the 82C t-stat, it will drive at 80C+. If I stop and let it idle, it will start to climb all the way.

    Changing the header tank back to it's previous location is not feasible as we changed the IC piping and it's in the way of where the tank was.
     
  16. rubjonny

    rubjonny Administrator Staff Member Admin

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    right so you can put the thermostat back to original, its not causing the overheat and will give you more problems in the long run as the engine will be running too cold most of the time.

    for earlier cars without a header tank sometimes people have to take the top hose off and fill the rad direct as they are a little more tricky to bleed. For it to work effectively the tank has to be higher than the engien ideally, plus the thin hose to it wants to be as high on the system as you can get it, and in a pipe which is always seeing coolant circulation even with the stat closed. MK2/3 golf usually have them in the radiator or the top rad hose. If you can plumb your tank into the factory pipes used for the 20v that should be fine anyway.

    have you read this, the bleeding method in there has never failed me:
    http://www.clubgti.com/showthread.php?145091
     
  17. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    I have the same problem on track but with oil temps, which will eventually overwhelm the cooling system given enough time.
    This is an ABF NA engine with significantly more engine power than stock.
    I am currently attempting to shortlist what is the root cause and a permanent fix is based on the history I have on my own vehicle.
    I am not going to list what has been changed due to time but I am narrowing how this phenomenon occurs to two sources before shelling out.

    Possibly exhaust backpressure transferring high EGTs to the exhaust port cooling jackets
    Actual undersizing of the double core alloy 16v radiator.

    JENVEE also runs an external MOCAL oil cooler in addition to the OEM Water to oil design.

    On road the trend is there to heat up the oil and more noticeable when ambients are over 20 deg C, with high part loads. However as you cannot legally/practically be flat out on the road there is no real concern.
    No issue at say 10 deg C ambient on the road, at any condition with oil temps no more than MFA 98 deg C on an Autobahn 110-115 mph sustained for 15mins or so.
    On a track over an MFA 130 degs seen for just 15mins of track time!

    *MFA readings are from a VDO cluster with matched OE senders.

    Money has been spent on quality components and OE parts, including an engine bottom end change with no impact on the issue.

    So my point is you have done the right steps but the root cause is likely to be elsewhere. I suspect at full chat on a boosted engine as yours,
    Your cooling system is unable to reject the heat energy from the engine when it is at its max friction, back pressure, and combustion temps.
    Without my own conclusions on my own vehicle, my gut feeling is to be track suitable, you will need to look at the radiator sizing and maybe the oil cooler sizing, on the basis your engine is the usual VW EA113 1.8T design, water pump in is good nick and along with a known stat.
     
  18. HidRo Forum Member

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    I will try to bleed the system once more, and try to pull the header tank higher (holding it with my hands.) to see if it burps.
    This is how it's at the moment.
    The header tank is above everything I believe.
    IMG_20170821_183809.jpg

    As for the exhaust gases. Would this be something to consider, if we are talking about overheating at idle as well (not only on track, pushing hard)?
    I have no oil cooler other than the stock water/oil cooler. But Oil temps were up to 72C the last time I tested the overheating at idle.
     
  19. Nightroamer Forum Member

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    If it's overheating and the oil is still only at 72C I would think it's not an issue of oil heating the coolant. Just my two pence.



    Sent from my iPhone using Tapatalk
     
  20. Nige

    Nige Paid Member Paid Member

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    Eddie, my understanding is nothing had changed hardware wise, the engine was fine and suddenly started overheating. Which would suggest that the cooling system was up to the job, then something happened.?
     

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