"CLUNK" IN RAD/HEATER HOSES

[STEVEN N]

'91 XLT
- OUTDOOR TEMPERATURE IS BELOW FREEZING
- TRUCK WARMED UP
- HEATER ON FULL BLAST
- THERE IS A SPURATIC LOUD CLUNKING SOUND(AND FEEL)IN THE UPPER RAD & TWO HEATER HOSES. SOMETIMES FOLLOWED BY A CLICK.
IT FEELS/SEEMS LIKE AN AIR POCKET MOVING IN THE
HOSES.
- USED 1 INCH OF COOLANT IN 7 MONTHS.
- CAN FIND NO COOLANT LEAK. EVEN CHECKED FRONT FLOORS UNDER MATS INCASE THE CORE WAS LEAKING.
THE NOISE CARRIES ON FOR ABOUT 2 MINUTES AFTER THE TRUCK IS TURNED OFF.
IT DOES NOT HAPPEN IN THE SUMMER,BUT THEN I DONT HAVE THE HEATER ON.
THE RAD HAD A LEAK SO I REPLACED IT, RAD CAP, THERMOSTAT AND RAD HOSES.

THE HEATER MUST BE ON FOR THE NOISE TO HAPPEN.

ANY SUGGESTIONS WOULD BE APPRECIATED.

 

[dogfriend]

I found a TSB that describes a thumping noise in the cooling system for the 94 - 97 4.0L. It says to replace the water pump with another design because of uneven flow in the cooling system.

If you email me, I can send a PDF of the Technical Service Bulletin.

 

[Ross-N-Chicago]

No need to do that. I would try burping the system first. Two ways to do are park on steep incline and release pressure cap--BE CAREFUL--and squeeze the upper rad hose a few times, the bottom one too. Or, when engine is COLD you can remove pressure cap, start truck and watch your coolant level and when you see it start to rise back up the filler neck put the cap back on.

Or, and this worked for me, my mechanic reversed my heater hoses and I had the same clunking and thumping you are describing. I switched em back and was fine. Hope that helps.

 

[dogfriend]

I also found another TSB that describes adding a coolent bypass kit for a similar problem. I could email that as a PDF as well.

I would try the burping procedure first.

 

[keithtaylor]

If anyone knows the cure to this, I would love to know. I have spent TOO much money trying to fix this already, I have a new radiator,water pump, 3 new thermostats, fan blade, and fan clutch, and finally a new cap.....HELP!

 

[dogfriend]

Check this thread

Dead Link Removed

I posted two TSB's which are related to thumping noise in the cooling system.

 

[Blaine122300]

Seems to mostly happen in 91's. I brought mine to Ford for the same problem. They told me there is nothing that can be done about it. It doesn't hurt anything by making the noise. It is just the pressure regulating itself in your heater core. Imagine a 2 liter bottle filled with water, turned upside down to let the water out, and air has to get in there somehow, so it goes in the same way the water is going out and makes that same sound. My X has been doing this since I bought it, and it hasn't hurt anything. My suggestion would be to just live with it.

Andy