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Air Bubbles in Radiator Overflow

Discussion in 'Stock 1995 - 2001 Explorers' started by Waltru, January 25, 2011.


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    1. Waltru

      Waltru New Member

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      I just posted in this thread but I thought I should start a new one from me as well: http://www.explorerforum.com/forums/showthread.php?p=2635364#post2635364

      I am having a problem with my 2000 SOHC with 120k. From a cold start the thermostat won't open until I get full hot on the gauge and the warning light comes on. When it does open after a few seconds the gauge falls back to normal and the heater starts blowing hot air.
      I also have the bubbles in the overflow tank when the engine is running and they continue for a minute or so once I shut it off. It does look like it's boiling from where the rad overflow hose enters the tank. When I get home from a drive I find the lid for the overflow tank will have popped open from the air pressure and coolant has slopped out of the tank.
      My gut is head gasket but I'm hopeful that a cracked thermostat housing maybe letting all this air in. There is no check engine light and the engine seems fine except for a low idle speed when in Drive (~500 rpm).
      I guess a compression check is my next option unless anyone has any other ideas?
      Has anyone tried bars leak - type products for head gaskets?
      Thanks!
       
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    3. 1AJeremyD

      1AJeremyD Well-Known Member

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      I wouldn't recommend using any form of leak prevention products. Sounds like a bad thermostat housing/thermostat. Change it instead of trying to add something to the radiator. Once you add that sort of thing you will never be able to flush it out afterwards
       
    4. swetrid

      swetrid Well-Known Member

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      thermostat
       
    5. OneLever

      OneLever Active Member

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      Good job on describing the issue. You identified the likely main problem since the thermostat is supposed to open well before internal engine temperature reaches the "High" point on the gauge as others have stated.

      Here is an excellent write up for your motor by AeroRamer: Link
       
    6. Waltru

      Waltru New Member

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      Thanks guys. I've seen reference to cracked thermostat housings on other postings. Will that allow the amount of air in that I see bubbling away in the overflow tank?
       
    7. TOMANDPAT

      TOMANDPAT Active Member

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      My daughter's 2000 4.0 OHV had the bubbles in the overflow tank problem that you describe. I replaced the radiator cap, that solved the problem. However, once the system pressurized properly, the intake gasket started leaking, so I had to replace upper and lower gaskets

      Tom
       
    8. my98nnj

      my98nnj Well-Known Member

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      Definately head gasket.

      Your getting exhaust gases into the cooling system. Those gases are being trapped probably by the t-stat and other higher areas causing the no-flow condition and the spike in temp you see before any cooling starts.

      Have a shop verify this with a sniffer at the overflow bottle. It will ID the gases.
       
    9. Waltru

      Waltru New Member

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      That's a good idea to get it sniffed. Thanks for the suggestion.
       
    10. Waltru

      Waltru New Member

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      I'm still messing with this in my driveway. I tried pressure testing the cooling system today but I couldn't get the adapter to seal with the neck of the radiator (and yes it was the correct adapter!). There is a slightly raised ring inside the radiator neck around the opening where the cap should seal against, but it seems to be kind of chewed up. I sanded it a bit smoother with some 80 grit paper and put some vaseline on the pressure test adaptor and that sort of worked. I was able to pump it up to 15 psi but I could still hear it hissing slowly out.
      Has anyone come across this before? Would a poor rad cap seal draw air into the cooling system? I really don't want this to be a head gasket...
       
    11. TOMANDPAT

      TOMANDPAT Active Member

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      If you were getting exhaust gasses in the cooling system due to a blown head gasket, you'd be able to see bubbles in the radiator with the cap off, engine running. Back in the day, before sniffers, that's how we checked for a blown gasket

      Tom
       
    12. my98nnj

      my98nnj Well-Known Member

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      That's pretty much what he's got happening.

       
    13. 1998Exp

      1998Exp Active Member

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      Overpressure is needed for the cooling system to operate properly and for the engine to reach normal temperature. If the radiator cap is not sealing, the coolant will be constantly boiling and escaping to the overflow bottle. This will probably also prevent sucking the coolant back when the engine cools down.
      It may not be your main problem, but should be taken care of.
      By the way, how did that damage happen? Perhaps someone used a cap with the rubber gasket missing?
       
    14. TOMANDPAT

      TOMANDPAT Active Member

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      I didn't see any reference to bubbles in the radiator in his posts. If that's what he's got, then he's got more problems than a radiator cap
      Tom
       
    15. joe doe

      joe doe Active Member

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      a non sealing rad cap can definitly let it boil over .i was going to say change the stat and get a new cap .
       
    16. Waltru

      Waltru New Member

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      I just got this truck 10 days ago because my old one was written off when someone ran a stop sign in front of me. Not sure how the damage to the rad neck could have happened on my current one.
      Thanks for everyone's ideas so far - I'm going to do a full cooling system flush now and start fresh with clean water and no air bubbles. I also see a good used rad on Craigslist for 30 bucks that I think I should go get...
       
    17. Waltru

      Waltru New Member

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      A new rad cap, radiator, thermostat and Rislone BarsLeak head gasket repair have not cured my problem.
      I see a 2001 Mazda Ranger engine on craigslist with about 83k miles on it for $750 that might make more sense than messing around with a head gasket or possible cracked or warped heads.
      Should this fully dressed Mazda Ranger SOHC be a straight swap?

      http://vancouver.en.craigslist.ca/pml/pts/2197600179.html

      Thanks for everyone's help so far...
       
    18. OneLever

      OneLever Active Member

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      A stop-leak additive can only do so much it will not work miracles on a blown head gasket. Unless you overheated the engine I doubt that the heads would be warped. New gaskets all around (both intake and the heads) would still run less than half that cost if you do them yourself. With an engine who's history you know on top of that.
       
    19. Nasty Exploder

      Nasty Exploder New Member

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      Just read thru this thread......1st check, rad cap, then thermostat, still have bubbles ? Headgasket FOR SURE !!!!, you can try some awesome stuff called IRONTITE, I have seen it hold a headgasket together for more then 7 years after treatment, and the motor was POURING out white smoke and antifreeze comming out of tailpipe....... It is still driving to this day with no new headgaskets.....this will only work provided the heads are not cracked or warped.
       

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