abarth cars - community > fiat abarth 1300/124 coupe

cooling system help

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My 1300/124 is boiling all its coolant out the upper hose that goes between the external thermostat and the coolant header tank, you can see the setup in the attached photo.  With the "radiator" cap on the tank, coolant goes out the overflow pipe onto the ground when operating temperature is reached.  With the "radiator" cap off the tank, it just boils the coolant in the upper hose and splashes out the top. The car runs and drives very well, no smoke or steam out the exhaust, the front radiator hoses get hot, as does the heater core.  As I have done with 124 TC cars with closed systems and overflow tanks, I have bled it all carefully several times but no help.  What's my next move?  Trouble shoot the thermostat and water pump?  Thank you for any advice and experience.

Eric, San Diego

Hi Eric, I think you still have air trapped in the system.  I am not sure on the correct procedure to deal with this, and defer to one of the experts here.  Your engine bay looks pretty nice.  I hope mine looks like that some day!


Hi, Eric,

What temperature is the coolant that's coming out, or what is the temperature of the hose or tank from which the coolant is boiling out?   In other words, is the coolant coming out because it is above its boiling point, or is the system over-pressurized from something else? (Like a blown headgasket leaking high pressure gas into the system.)

Is the radiator cap the correct pressure?  If its too weak the coolant may boil out at a lower temperature.

How did you bleed the system of air?  Does the front radiator have a bleed screw?

Jim Oddie

Hi Gil and Jim,

I too think it's behaving most like there's unpurged air in the system somewhere, so I'll have another go at bleeding it out and try a higher PSI cap before tearing it apart again.  It is a 10 PSI cap right now.  I have heard that 12 to 13 is okay and 14 is pushing it.

There's no problem until it has been running for a while and is good and warmed up, then coolant comes out of the header tank steaming hot.  There is a bleed fitting on the upper portion of the front radiator, and I have been told there is another on the heater core which I have not yet found.

I don't think it's a head gasket or cracked head or block, because there is no oil in the coolant and vice versa, there is no smoke or steam from the exhaust, the compression tests out fine, and the plugs look fine.  And it really runs well.  But I sure would like to fix the problem before it leads to such disasters!

Thanks for your thoughts, there is no diagram and explanation of how this goofy system works that I have yet found.  It most closely resembles the external T-stat found on late '70's 124 TC engines, but with an extra bypass hose grafted on.  Another owner said he put on a BMW 2002 T-stat and simply blocked off the extra hose.

Eric, San Diego

 The metal expansion tank is supposed to vent excess pressure &/or coolant out of the small open-ended hose when the system is hot, similar to the tank on a Fiat X1/9. When the system gets hot & the coolant/water mix expands, the tank's radiator-style cap dumps out the excess pressure via the small hose that points towards the ground. Technically, it is not a coolant overflow/recovery reservoir like the standard 850 plastic tank. It's more like the set-up on a Fiat 600 radiator, which has just a small dump hose connected to the radiator cap neck/fitting on top of the radiator, with the hose running down the side of the radiator & dumping excess coolant onto the ground.

 If your 1300 cooling system is topped-off full, then you run the car up to temp & the system vents a bit, that would be normal (should not be a huge amount of coolant lost, though). Let the car cool down (say, overnight), then without refilling the system, run the car back up to normal temp & see if the system stays even (doesn't vent coolant out). If it stays even, you're fine. If it doesn't stay even (continues dumping lots of coolant), there may either be air trapped in the system, or you may have a leak somewhere letting air in & causing the coolant to boil (system is not holding normal pressure). On 850's, 99% of the time it's a faulty cap or corrosion/damage around the opening for the cap (your cap looks new, but I just wanted to let you know this). ;)

 You might also want to check your pipes for any pinhole leaks. Easy way is to run the car up to temp, then keep the car idling & put the front of the car up on ramps, crawl/slide under & inspect pipes. This way your system will be under pressure & any leak(s) may be easier to see/hear.

--- Quote from: evannice on August 08, 2007, 06:56:03 am ---There is a bleed fitting on the upper portion of the front radiator, and I have been told there is another on the heater core which I have not yet found.

--- End quote ---

Bottom left corner of this photo:


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