KR engine coolant light flashing intermittently

Discussion in 'Electrical' started by Onslow, Feb 5, 2020.

  1. Onslow Paid Member Paid Member

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    My 1988 KR engined Mk2 Golf with a CE 1 fusebox has started intermittently flashing the coolant light after a couple of minutes running.
    At one time it was also stalling after the coolant light had been flashing. It seems to have stopped stalling recently.
    So far I have replaced the level sensor in the reservoir and 4 of the water temperature senders on the block.
    I also checked and cleaned the connections in to the ECU.
    I am still getting the coolant light intermittently flashing...

    The rad fan has also been intermittent in cutting in despite replacing the radiator thermal switch. I am considering replacing the 4Life waterless coolant, but have to say that the car has been running fine on it for years.

    Any help or suggestions appreciated.
     
  2. costel1969

    costel1969 Paid Member Paid Member

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    Not sure about the stalling element but in relation to the cooling light I would do the following:
    Remove and clean or replace the coolant bottle and cap - they can lose efficiency and start to deteriorate over time. Next, unless you've done it already empty the system, flush it and replace the coolant - the system may be silted up and they don't like that and while you're at it, replace the stat and check/replace any questionable hoses. How old is the water pump? - worth checking/replacing that as well.
    Hope this helps
     
  3. rubjonny

    rubjonny Administrator Staff Member Admin

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    1st step loop a wire between the 2 pins on the level sender, if that stops the light flashing then the relay is having trouble with the coolant mix or its slightly low. if the light carries on flashing intermittently pull the 42 or 43 relay out of the socket above the fusebox. if that stops it the relay is bad or you have poor contact on a terminal somewhere or corroded wiring. if it STILL does it have a good look at the yellow/red sensor wire make sure its not chafed anywhere and shorting. also have a look at the clock plugs make sure the wiring is good here and the pin terminals are not squished down and loose on the pcb contact pads

    the radiator fan should only cut in around 3/4 on the gauge, during the winter it probably wont cut in that much if at all depending on your driving and overall condition of the cooling system. to check the wiring pull the thermoswich and loop a wire between the pins and your fan should run. look at the 2 pin plug which joins the fan loom to the headlight loom its an unsealed connector and corrosion can build here.
     
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  4. Onslow Paid Member Paid Member

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    Think we crossed there rubjonny!

    Thanks Costel,

    I am going to go for flushing the system through.
    Having said that the radiator and nearly all the hoses were replaced 4 years ago. I have tried several rad thermal fan switches and when I have done that the coolant I saw didn't look particularly contaminated.
    When I replaced the temp sender to the dash I didn't see a lot of coolant leak out and I wonder if I have had an airlock?

    The coolant reservoir (original) has a new blue cap on it.
    The water pump and thermostat (replaced 4 years ago) appear to be working fine as when I use the car with the fan switch disabled the radiator gets warm and the temperature on the gauge sits in the middle.
    To try and diagnose the flashing coolant light yesterday evening I went to bypass the level sensor in the reservoir. I wasn't impressed to see coolant weeping through the electrical connectors on the (new) sensor! I am going to put the old sensor back in when I replace the reservoir. Bypassing the level sensor did not stop the light flashing...

    In other areas I had convinced myself that the stalling was down to the ISV and that this might be related to a loose wire (green/black) to a sensor on the back of the head. Having reread through rubjonny's posts I see that this is for a oil temp sensor for mfa. I am going to remake that and also check around the ISV (again...)
     
  5. Onslow Paid Member Paid Member

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    Thanks rubjonny. Will try those suggestions.
    Interested in your comment about the fan cutting in at 3/4. Previously I have had it cut in at about 6/10 (ish) but will have another look at it.

    The green/black oil temp sender on the back of the head looks to have been replace with a black one rather than white. That doesn't seem to have affected the readings on the MFA.
     
  6. rubjonny

    rubjonny Administrator Staff Member Admin

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    there can be a bit of variance in the dash readings, for my example when driving along the gauge would be at around 1/2 (90 degrees) then fan cut in around 3/4. you may find your gauge sits a little higher or a little lower, its all fine just as long as you know where your engine sits normally then you know if its running hotter or colder than usual.

    with the mfa sensor the original VW ones are white, but if its had an aftermarket one these may not be the same colour. see if there are any VW part numbers on it anyway
     
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  7. Onslow Paid Member Paid Member

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    Understood. I have been swapping new sensors in, so that may account for a change in apparent temp changes.
    Will have a look at a few things and take it for a test drive.
     
  8. Onslow Paid Member Paid Member

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    I have flushed the cooling system through. The fluid that came out wasn't particularly dirty, but I replaced it with clean stuff.
    I also refitted the original level sender in the reservoir not being happy with the new one I had bought.
    When I started the car in order to get any air out of the system, it took a while for the bottom radiator hose to get warm.
    That had me worried that there was a thermostat problem, but it eventually got hot...

    At the same time as I was doing this I found an old ISV I had stored away and cleaned it up and installed it.

    Took the car for a run around the block. The rad fan kicks in at 3/4. (-Have to say that is later than it used to and I get apprehensive watching the temperature get up towards 7/8.)
    At no stage did the coolant light flash.
    The car cut out several times, usually when I had lifted my foot of the accelerator which makes me think the ISV I fitted is duff. Having said that it buzzes when I turn the ignition on. I am going to refit the original ISV as the car cut out less using that one.

    The oil temp sender is the correct one i.e. white (it was just covered in crud which made me think it was black!)

    The relay in the position for the coolant warning light is not a 42 or a 43 but has 21 written on it instead.

    Is it worth mentioning that in the past when the car has cut out and I have restarted it the clock has zeroed itself?
    Have to confess in the heat of the moment I haven't noticed if it has zeroed before I restart. At one point his had me wondering if there was an electrical reason for the cutting out.
     
    Last edited: Feb 6, 2020
  9. Onslow Paid Member Paid Member

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    Further to the above having put the old ISV back in and put the original level sensor back in the reservoir I went for a short drive.
    The coolant light flashed and the car cut out. I shorted out the level sensor, but still get the coolant light flashing so that suggests the relay.
    The car stalled and this time I noticed that the clock had zeroed before I restarted it.
    It also zeroed whilst I was driving and I had the car cut out several times.
    Coasting to a halt outside the house with the ignition live I felt the ISV..no buzz. Cycled the ignition and the ISV was buzzing.
     
  10. rubjonny

    rubjonny Administrator Staff Member Admin

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    if the cooling system is healthy the bottom hose should stay stone cold till gauge gets to around 1/2, so all is well there :)

    The 42/43 relay on the CE1 fusebox is located in a socket above the fusebox, the socket has black/yellow, brown, blue/red and either yellow/red or yellow/blue wires out the back of it. 21 is an indicator relay should be in the fusebox, so sounds like things have been messed about with:
    https://clubgti.com/forums/index.php?threads/fusebox-faq.219775/

    first thing I would check all the battery, starter and alternator cables, remove and give them all a good buff up. if the battery earth goes to the top of the gearbox bracket, I would change it to later mk2 location which is on a stud on the end of one of the 2 upper bolts holding gearbox to engine. corrosion builds between box and bracket preventing good contact so VW moved it. if you can find a mk3 golf in local scrappy I pinch all the cables off it as they're usually in good nick and have nice battery terminals. you may have to make a short extension from the stud behind the battery if the mk3 ring doesnt quite reach.

    since its got the CE1 fusebox the earth for the clocks goes to the side of the head, so if your box earth is a bit poor this could explain why it looses time, but its also a symptom of a weak battery. my mk2 had started to loose time sometimes on a cold start even though it cranked over and started fine, but when I put a new battery on the difference in cranking speed was night and day

    if you find the car is cutting out on over-run this may be an issue with the over-run cut off valve behind the air box, its the larger plastic one. check the wiring to it and the hose connections, the plug should have a black/yellow and black/brown wire. the black/yellow is ignition live and the black/brown is earthed by the isv control unit. have a good go over on the wiring to the engine while you're there, unplug the ecu, ignition amp, distributor etc make sure the pins are clean, tight and fully inserted in the plug. peel back rubber boots where you can to check wire condition underneath. on the side the green/red wire goes to the ISV control unit sensor, blue/white the ecu and yellow/black the dash. you can swap these wires between the 3 sensors as they're all the same rating. if one reads off compared to the other 2 on the dash then this is a sign you have a duff sensor

    worth having a look through this as well:
    https://www.clubgti.com/forums/inde...air-and-tune-your-mk2-corrado-1-8-16v.195423/
     
  11. Onslow Paid Member Paid Member

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    Thanks, will look in to that.
    Your comments about the battery have got me thinking. It was one of the first things I checked. (12.* v engine off, 14.*v engine running.) It is a replacement battery for one I had under warranty that had failed. Same brand, wonder if they have lost the ability to make decent batteries...
    Will look in to your suggestion regarding the earth strap.
    Apologies, was looking in the wrong place for the coolant relay. (Dohh!) Have now found relay 43
     
  12. rubjonny

    rubjonny Administrator Staff Member Admin

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    mine would be 12v engine off but the voltage dropped off just that little bit too much while cranking, it had been going bad for years just only this winter it got so bad my clocks would cut out.

    but if the clocks reset when the car cut out rather than when you attempted to restart the car this would point towards a wiring fault rather than battery :)
     
  13. Onslow Paid Member Paid Member

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    Success!

    Whilst following your suggestions rubjonny I went to check the the over-run cut off valve behind the air box and saw that the air pipe that it is inserted in to was not properly home.
    Having reseated it I have been out for a couple of test runs and everything is back to normal. No cutting out and no flashing coolant light.

    The flashing coolant light had me concerned that there may be a wiring problem and i had a look around the back of the fusebox where there had previously been a problem with one of the earths. All seemed OK and I made sure everything was properly connected.

    It is a bit of a mess round the back of the fusebox following three different alarm immobilisers being (professionally) fitted.
    There was an unterminated lead off the "P Red 7 pin 7 single point connectors for terminal 30 circuit" part of the board. Concerned that this was live and might be shorting out I removed it. I think it was left there by someone when they had the radio on a different circuit. i.e radio working with the ignition off.

    Behind connection K on the fusebox there is a 4 pin clear connector that is not connected to anything. It is 4 pin where as K where I thought it lived is 5 pin. I have searched the fusebox FAQs but cannot work out what is. Despite it not being connected to the back of the fusebox everything seems to work OK.
    Any ideas what it is for?
    IMG_5245a.jpg

    Thanks again for your input rubjonny (or may I call you John?). You are a VW Hero!!
     
  14. rubjonny

    rubjonny Administrator Staff Member Admin

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    good stuff :)

    that extra 4 pin is an unused connection, its part of the wiring loom for heated seats. for whatever reason on the fusebox half of the dash harness this is often fitted even on cars without seats specified. probably to reduce complexity in production
     
  15. Onslow Paid Member Paid Member

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    Phew ! [:D]
     
  16. Onslow Paid Member Paid Member

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    Meant to add I am going to follow up on your suggestion of improving the earth to the engine...:thumbup:
     

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