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1G Is it normal for your coolant to pressurize while doing a BLT?

Posted by mitsuowner1991, Jun 21, 2020

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  1. mitsuowner1991

    mitsuowner1991 Proven Member

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    I checked my coolant after A BLT and there was pressure.
     

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  2. Hickory-NC-2Ggsx

    Hickory-NC-2Ggsx Proven Member

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    Sounds to me like a blown headgasket or a cracked head. Are you over heating or losing coolant at all?
     

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  3. mitsuowner1991

    mitsuowner1991 Proven Member

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    No.. it gets to normal operating temp and stays there.

    The engine has less then 1000 miles on.. with a new head gasket. Could it be I have to retorq the head down ?
     
    Last edited by a moderator: Jun 22, 2020

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    88  1

    03 Volkswagen Jetta 1.8t
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  4. pauleyman

    pauleyman DSM Wiseman

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    Given your other post about fiav and idle issues id start there. Are coolant lines looped at throttle body?
     

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  5. mitsuowner1991

    mitsuowner1991 Proven Member

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    They are still connected to the TB.
     

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    rwd · manual · Misc Vehicles

    88  1

    03 Volkswagen Jetta 1.8t
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  6. Sniffbooger

    Sniffbooger Proven Member

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    Wouldn't it be prudent to do a simple block test with the test liquid to determine if there is a head gasket issue instead of guessing and trying to figure out how to remedy something without knowing exactly what the underlying issue is to begin with?
     

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  7. mitsuowner1991

    mitsuowner1991 Proven Member

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    It would be "prudent" I just didn't think that was the problem. It had almost new pistons and rods and was boored over 20..... The car ran fine before I had a collant leak in the throttle Bodie. So I put a new gasket and sensor in and adjusted the tps .. so I did a BLT and found leaks. So I fixed them.. like I said the car ran fine with gummed up coolant in the TB except the throttle would stick. So I clean3d up the TB and it doesn't stick anymore and no more coolant leak or boost leak except I noticed the coolant pressurizes... How would I do a block test?
     

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  8. benspilk09

    benspilk09 Proven Member

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    Did you replace the seal in the FIAV?
     

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  9. mitsuowner1991

    mitsuowner1991 Proven Member

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    Yes
     

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  10. 91talonts1

    91talonts1 Proven Member

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    I would take pauleyman's advice and start at the FIAV since you already had problems there and it's pretty simple to rule out. Disconnect the coolant lines from the TB and do another boost leak test. If air leaks from the FIAV nipples you've found your problem.
     

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  11. mitsuowner1991

    mitsuowner1991 Proven Member

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    The car holds 15psi for a couple minutes during a BLT.

    If air air leaks from.the fiav then it's bad? I should just loop the lines and get the plate to iliminate it.
     
    Last edited by a moderator: Jun 22, 2020

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    rwd · manual · Misc Vehicles

    88  1

    03 Volkswagen Jetta 1.8t
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    1991 Mitsubishi Eclipse GSX
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    1991 Mitsubishi Eclipse GSX
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  12. Sniffbooger

    Sniffbooger Proven Member

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    Figuring out mechanical problems is a logical process of elimination. One can miss something if they operate under the assumption that 'the car ran fine before, so it cannot be X', or 'X' was just replaced, so it cannot be 'X'... I've had gaskets, throttle bodies and sensors replaced only to find that it wasn't done properly, or a new part was faulty out of the box...

    Also, just because it 'ran fine before', doesn't rule out the possibility of an underlying issue...cars can still run with vacuum leaks and head gasket issues.

    So go to AutoZone, rent/borrow the block tester kit and buy the test liquid. It measures combustion gases in the coolant. There should be zero. That should rule out a leaky head gasket or a cracked head.

    You should not have a pressurized cooling system just from a boost leak test.
     

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  13. mitsuowner1991

    mitsuowner1991 Proven Member

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    I will check this out but I really doubt it's the head gasket. There's less then 1000 miles on the rebuild.. and I've babied it those miles. Also there isn't any coolant mixing with my oil when I changed the oil.
     

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    rwd · manual · Misc Vehicles

    88  1

    03 Volkswagen Jetta 1.8t
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    1991 Mitsubishi Eclipse GSX
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    1991 Mitsubishi Eclipse GSX
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  14. pauleyman

    pauleyman DSM Wiseman

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    No. Loop the lines for the coolant. Then do another boost leak test. If air comes out of the coolant nipples on the throttle body you found your problem.
    I think all of you troubles lie in the throttle body. It seems to be the common denominator.
     

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  15. mitsuowner1991

    mitsuowner1991 Proven Member

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    So if air comes out of the nipples what is wrong??
     

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    2005/HONDA/CBR600RR
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    88  1

    03 Volkswagen Jetta 1.8t
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    1991 Mitsubishi Eclipse GSX
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    1991 Mitsubishi Eclipse GSX
    · 1G DSM
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  16. Hickory-NC-2Ggsx

    Hickory-NC-2Ggsx Proven Member

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    Yeah i had no idea you was having those issues. Id do as @pauleyman recommended and loop the lines then do a blt.
     

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  17. JeffGS-T97

    JeffGS-T97 Proven Member

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    Very good suggestion sir.

    A compression blown gasket can pressurize the coolant. The small area around the water jackets allow pressure into the cooling system and not give off any symptoms besides over pressurized coolant. Usually a faulty gasket or a warped head. But the cooling gasket in the TB was also very good suggestion.
     
    Last edited by a moderator: Jun 22, 2020

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  18. pauleyman

    pauleyman DSM Wiseman

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    You have something wrong in the fiav assembly. Possible new throttle body necessary
     

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  19. mitsuowner1991

    mitsuowner1991 Proven Member

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    I will test it... So if I loop the coolant lines and delete the fiav.. do I just unplug it and leave the plug ? I noticed when I had the TB off. The bids screw was all the way in. Tight!! I got it out tho.. I might get the block off plate and just delete the fiav..
     

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  20. mitsuowner1991

    mitsuowner1991 Proven Member

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    Also what should the head be torqed to? I'm gonna see if it needs to be re torqed... I haven't even put 1000 miles on the motor. I haven't even boosted hard either. As I'm getting older I baby my cars. Thanks for everyone's help.
     

    138  1

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    88  1

    03 Volkswagen Jetta 1.8t
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    1991 Mitsubishi Eclipse GSX
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    1991 Mitsubishi Eclipse GSX
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  21. TheFlashDSM

    TheFlashDSM Supporting Member

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    a bad head gasket, when the coolant enters the cylinder act like a steam clean for that cylinder(s), check your plugs and see if they like that have been cleaned, the cleanest plug(s) could be your problem cylinders
     

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  22. Sniffbooger

    Sniffbooger Proven Member

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    Be careful not to confuse the ISC solenoid idle control motor with the FIAV. The FIAV does not have a plug. It is an internal valve in the throttle body behind the little brass freeze plug activated by the coolant to give a fast idle when cold. To disengage it is to bypass it with a blockoff plate. I thought that is what you installed already.

    Leave the ISC plugged in. It controls the idle at operating temperature.
     

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  23. pauleyman

    pauleyman DSM Wiseman

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    I think youre confusing what is what on the throttle body. There is no plug for the fiav. There IS a plug for the isc. From all of this discussion I think you have an internal leak in your throttle body associated with the fiav and its associated block off. If you loop the coolant lines then they are no longer connected to the throttle body. Conduct a boost leak test under those conditions and if air comes out of the throttle body coolant fittings you found your air leak and why the coolant system was pressurized. This is where I would start.
     
    Last edited: Jul 17, 2020

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  24. CKOPOCT

    CKOPOCT Probationary Member

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    What everyone has said are good suggestions and possible causes of a pressurized cooling system. Bench wrenching is tough and often leads to rabbit holes and false conclusions simply because you aren't there to witness stuff and get first-hand details important to draw conclusions. Often times the biggest challenge one comes up against when trying to diagnose a problem, especially a problem on one's own car, is overcoming one's own biases. Biases like new parts can't be the cause of the current problem, because new parts are good out of the box.

    That said, the best approach is to assume anything can be the problem. So start with what has been most recently touched or worked on that has a part to play (TB). If that checks out, next go to the most likely and common cause of cooling system pressurization (head). Go from there.

    I have a suspicion PauleyMan is on target. Good luck!
     
  25. mitsuowner1991

    mitsuowner1991 Proven Member

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    Ok so I'm doing test on the car today.. someone said to remove both coolant lines from the bottom of the throttle Bodie and then do a boost leak check. And if air is coming out then my fiav is bad.. I think I'm gonna order the block off plate. I currently have the BYPASS PLATE.
     

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    03 Volkswagen Jetta 1.8t
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    1991 Mitsubishi Eclipse GSX
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