Deville pressure build up in coolant system.
Cadillac
 

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds / (Old System)

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors

CadillacForums.com is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Page 1 of 3 1 2 3 LastLast
Results 1 to 15 of 31
Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, Deville pressure build up in coolant system. in Past Cadillac Vehicle Discussion; my car runs fine except for the crank sensor malfunctioning now. does not over heat til most of coolant is ...
  1. #1
    mrqvellie is offline Cadillac Owners Member
    Automobile(s): deville
    Join Date
    Nov 2012
    Age
    41
    Posts
    6
    my car runs fine except for the crank sensor malfunctioning now. does not over heat til most of coolant is pushed out of reservoir. this can be noticed by heat going out and when you rev the engine temp goes down heat comes on. all fluids are clean. tail pipe exhaust is normal. i flushed the system. replaced the fluid. Did the head gasket test kit, passed (only steam). Pressure tested, held 19 psi all day. I let it idle and drove it for hours (dove it at 80+mph). the next morning i drove it a couple of miles. no over heating but i noticed the cup i put the overflow hose in was full of antifreeze.I parked it and left it. went back to it two weeks later and coolant system was still under pressure. i have never experienced this. and ive fixed a lot of cars. even northstars. have any one ever experienced this. please help i dont want to do a head job for nothing.

    my car runs fine except for the crank sensor malfunctioning now. does not over heat til most of coolant is pushed out of reservoir and steam gets into system. this can be noticed by heat going out and when you rev the engine temp goes down heat comes on. all fluids are clean. tail pipe exhaust is normal. i flushed the system. replaced the fluid. Did the head gasket test kit, passed (only steam). Pressure tested, held 19 psi all day. I let it idle and drove it for hours (dove it at 80+mph). the next morning i drove it a couple of miles. no over heating but i noticed the cup i put the overflow hose in was full of antifreeze.I parked it and left it. went back to it two weeks later and coolant system was still under pressure. i have never experienced this. and ive fixed a lot of cars. even northstars. have any one ever experienced this. please help i dont want to do a head job for nothing.

  2. Remove Advertisements
    CadillacForums.com
    Advertisements
     

  3. #2
    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
    Automobile(s): Crimson 2001 Seville STS, 1990 Seville (RIP)
    Join Date
    Sep 2010
    Location
    East Boston MA.
    Age
    26
    Posts
    21,965
    I think you need to do the block test again. Take the car out and drive it HARD, then do the test.

    Was there ANY change in the color of the test fluid when you did the block test?

  4. #3
    basscatt's Avatar
    basscatt is online now Cadillac Owners 10000+ Posts
    Automobile(s): 89 Coupe DeVille, 95 Sedan DeVille, 03 SLS, two 02 DHS's
    Join Date
    Feb 2004
    Location
    Minnesota
    Age
    63
    Posts
    10,102

    Re: Please help deville pressure build up in coolant system.

    went back to it two weeks later and coolant system was still under pressure.
    that's NOT right -
    the cooling system - when cold - is not pressurized -
    pressure develops as the antifreeze gets heated and expands -
    once the antifreeze cools back down - the pressure is gone -

    the only possible way a cooling system can be pressurized cold -
    is from exhaust gasses being pumped in due to bad head gaskets -

    Did the head gasket test kit, passed (only steam).
    try the test again -
    there are several YouTube videos showing the proper way to use the equipment -
    and the expected results -

    the blue test liquid reacts with hydrocarbons - exhaust gasses -
    ANY COLOR CHANGE - even a slight change to a lighter blue -
    is a positive reaction -

  5. #4
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
    Automobile(s): 2002.5 F55 STS/65500mi, 2004 Ford F150 SuperCab4x4
    Join Date
    Feb 2006
    Location
    MD Eastern Shore - Kent Island
    Age
    74
    Posts
    45,025
    What year, what model ???

    If it's a Northstar the coolant reservoir should be half full, cold. No more than that.

    I made your thread title a bit less generic .................

    mrqvellie, Please do not multiple post the same question in multiple forums - this is the third identical thread you have started. The other two have been deleted. Thanks for the consideration.

  6. #5
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    73,941

    Re: Deville pressure build up in coolant system.



    all fluids are clean
    Irrelevant


    tail pipe exhaust is normal
    Again, irrelevant. You generally won't see any steam in the early stages of a HG failure on a Northstar.


    Pressure tested, held 19 psi all day
    That's good for locating an external leak, but won't show a HG leak.



    I think you need to do the block test again. Take the car out and drive it HARD, then do the test.

    Was there ANY change in the color of the test fluid when you did the block test?

  7. #6
    mrqvellie is offline Cadillac Owners Member
    Automobile(s): deville
    Join Date
    Nov 2012
    Age
    41
    Posts
    6

    Re: Deville pressure build up in coolant system.

    i did the fluid stayed blue. i graduated auto tech a little while ago. i am pretty knowledgable mechanically. these northstars are tricky. the problem with pushing it hard then doing the block test is when you open it whatever is in there is released. also if exhaust gas is getting in it has to get back out the same way. the system held pressure with all spark plugs removed. i read somewhere earlier about a purge valve. ive done 3 NS head jobs before 2 successfully. neither did what this is doing. this one almost seems as though it has a air pocket or restriction. sorry for the extra posts. im new did think iwas putting them in the right place for a thread.

    ----------

    im gonna try running hard and rigging a contraption to catch whatever vapor is in there and test it.
    funny thing is when i fill it with fluid and after it is purged out. it stays full to the top. even now a 20 ounce cup purged out and it is full to the rim.

  8. #7
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    73,941

    Re: Deville pressure build up in coolant system.

    also if exhaust gas is getting in it has to get back out the same way.
    Not necessarily. Remember, IF the system is being pressurized by exhaust gases, the cylinder pressure forcing those gases into the cooling system is FAR, FAR greater than the 19 psi produced by a cooling system pressure tester. A pressure tester will not have anywhere near enough pressure to force coolant back into the cylinder with a very small HG breach or in the case of a Northstar, a pulled thread on maybe one bolt which reduces clamping pressure on the head enough to leak a little when the engine is running.

    There is no purge "valve" on the Northstar. There is a purge "line". It is open all the time. It is the 3/8" line that runs from the WP housing aka crossover manifold to the surge tank. Any air in the system automatically gets into the line and flows to the surge tank. If the tank gets over pressurized, as in the case of a HG breach, excess pressure will then be expelled overboard via the cap vent, as you well know.

  9. #8
    mrqvellie is offline Cadillac Owners Member
    Automobile(s): deville
    Join Date
    Nov 2012
    Age
    41
    Posts
    6

    Re: Deville pressure build up in coolant system.

    im gonna try running hard and rigging a contraption to catch whatever vapor is in there and test it.
    funny thing is when i fill it with fluid and after it is purged out. it stays full to the top. even now a 20 ounce cup purged out and it is full to the rim. 2000 deville

    ----------

    thanks Ranger u absolutely right. i used my air compressor at plugs and pumped it well above 19 and listened for seepage. i chose 19 -21 to hold it at as i was taught and have diagnosed and traced down sources before. The NS is tricky. i had one where the itnterior surface of the head was not smooth. ran fine but as soon as u put pressure on it BAM! The car is mint with 9Ok owned by a ww2 sarg.

  10. #9
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    73,941

    Re: Deville pressure build up in coolant system.

    You're not filling the surge tank to the top, are you?

    I can understand an imperfect head surface. That would make sense. You just have to keep in mind how the Northstar works (or more accurately, how it fails). Like I said, generally speaking it's not a HG "breach". It's usually the head loosing clamping pressure, and that won't be a lot with only 1 or 2 head bolt threads pulled. Enough to seep when you put a load on it, but nothing from a few psi by a tester. Even 125 psi shop pressure in a cylinder doing a leak down test probably would not be enough to lift the head enough to leak compared to the enormous pressure built up in a cylinder when the fuel mixture is ignited. And when I say "lift" it's so minute it's probably not measurable.

  11. #10
    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
    Automobile(s): Crimson 2001 Seville STS, 1990 Seville (RIP)
    Join Date
    Sep 2010
    Location
    East Boston MA.
    Age
    26
    Posts
    21,965
    Quote Originally Posted by mrqvellie
    im gonna try running hard and rigging a contraption to catch whatever vapor is in there and test it.
    There'll be enough in the surge tank to test, as long as you're not overfilling it.


    funny thing is when i fill it with fluid and after it is purged out. it stays full to the top. even now a 20 ounce cup purged out and it is full to the rim.
    Once the coolant cools and contracts, it won't be up to the top anymore. And if it is at the very top when hot, you're overfilling it.

    thanks Ranger u absolutely right. i used my air compressor at plugs and pumped it well above 19 and listened for seepage.
    Compression pressure is 150+ PSI, combustion pressure is way beyond that. Pumping the cylinders up with an air compressor isn't going to tell you anything during the earlier stages of failure.

  12. #11
    mrqvellie is offline Cadillac Owners Member
    Automobile(s): deville
    Join Date
    Nov 2012
    Age
    41
    Posts
    6

    Re: Deville pressure build up in coolant system.

    Once the coolant cools and contracts, it won't be up to the top anymore. And if it is at the very top when hot, you're overfilling it:

    its filled to the top now cold and the system is not full of fluid. weird hunh.

  13. #12
    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
    Automobile(s): Crimson 2001 Seville STS, 1990 Seville (RIP)
    Join Date
    Sep 2010
    Location
    East Boston MA.
    Age
    26
    Posts
    21,965
    If it's not full, how is the coolant to the top of the surge tank?

    And if it is FULL to the top, it's overfilled.

  14. #13
    mrqvellie is offline Cadillac Owners Member
    Automobile(s): deville
    Join Date
    Nov 2012
    Age
    41
    Posts
    6

    Re: Deville pressure build up in coolant system.

    wow. i guess some xxxx comes from experience. i went and got the car. let more fluid out. checked the purge which was clogged. did the block test again and it passed. floored it. ran great. let it sit running then took it and floored it again. no pressure build up. the guy i bought it from thought maybe bad head but it actually had a bad water pump and he had it overfilled. wow. thanx guys.

  15. #14
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    73,941

    Re: Deville pressure build up in coolant system.

    I assume you cleared the obstruction in the purge line and it now flows coolant?

    P.S.
    The proper coolant level is 1/2 full (2/3 at the most).

  16. #15
    mrqvellie is offline Cadillac Owners Member
    Automobile(s): deville
    Join Date
    Nov 2012
    Age
    41
    Posts
    6

    Cool Re: Deville pressure build up in coolant system.

    yes i did. and it does. i bought it from a guy with possible head problem otherwise in pristine condition. but it drove way too long without overheating and when and you had to rev the motor to get heat. he had it full all the way to the top. i replaced the freespining water pump. and put it back like it was. wow never really thought about the fact that anitfreeze expands. i was about to rip it apart til i found yall page and seen the purge thing and decided to post. thanks guys (Ranger)i was literally minutes from ordering a 500 buck stud kit.

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Bookmarks

Cadillac Posting Rules

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
Read about Lincoln | Buick | Kia Forte Forum
Need products for your Cadillac? Check out your options at the links below:

custom floor mats | Cadillac Chrome and Black Chrome Wheels | window tinting