For the past few months, I have had a recurring overheating problem due to low coolant level. But - there was no puddle. No other traces of coolant leakage were evident - no milky oil, no bubbles in the radiator, no fouled plugs - nothing.

I had been checking coolant level every morning but the radiator seemed full. So, with a full schedule of fun, I neglected to check it for three or four days. On my way back from Monterey, all of a sudden the temps shot up. I got off the freeway and pulled into a roadside horse ranch.

As I was waiting for the beast to cool down, I tried bleeding the pressure off the system by lifting the relief lever on the radiator cap. Instantly, the lid blew off the overflow tank. The tank was full of coolant up to the neck and there were traces of coolant all over the wheel well, suspension and fender.

As the pressure hit the hose leading from the radiator neck to the overflow tank, I saw leakage at the radiator neck which trickled down the tank. All of a sudden my pea brain put two and two together. (You've probably already got this one all figured out.)

When the coolant gets hot it expands. A bit of coolant pushes its way past the cap and enters the overflow reservoir. As it cools off again on engine shutdown, it's supposed to suck back into the radiator. Because of the tiny leak where the hose meets the radiator neck, it was sucking air instead of coolant back into the syste, After a few days, the overflow tanks was - you guessed it - overflowing and the cooling system was full of air.

I was able to easily pull the hose off the connection to the radiator neck. It had an aircraft-type hose clamp which was fairly loose as well as oblong shape. Reshaping the clamp and tightening it took but a minute and the problem was fixed.

Just a hint for those who may have this sort of problem.

Rich


[Modified by Cap'n Rich, 9:30 PM 8/21/2002]

 

:cool: :cheers:

 

Very good catch. Have posted this many times, but your personal example will bring this home for many!

Also, you didn't explain why the coolant overflowed when you pulled the pressure vent. For those that don't know: When pressure is released from a hot cooling system the boiling point of the coolant drops from 250+ degrees to just over 212 degrees = instant boilover! The pressure cap provides almost all the boil-over protection in the cooling system - NOT the anti-freeze.

Pressure cap is also a common source of loss of coolant due to lower temp boiling. You at least have proven that yours is working!

Pete :cheers:

 

nice find! :yesnod:

 

:cheers:

 

:cool: :cool: :cheers:

 

I remember this from physics class but have wondered why there is a pressure release on the cap at all. When would you use it?

 

Excellent :cheers: . Good catch. It's something we all need to pay attention to.

 

If the temperature of the coolant is below its boiling point at atmospheric pressure, you can safely release the excess pressure in the system and remove the radiator cap. In my case, I didn't want to wait by the side of the road until the coolant reached "room" temperature before I removed the cap to add more. It is much safer to use the relief lever than it is to simply remove the cap when there is pressure in the system.

Never pull the lever or remove the cap when the temperature of the coolant is above its atmospheric pressure boiling point :nono:

I remember a case where a couple filled a thermos bottle with very hot (but not boiling) coffee and then went flying in their Beechcraft Bonanza. Upon reaching their 8,000' cruising altitude, the wife opened the thermos to have a cup. At 8,000', the coffee was now above its boiling point and all of it flashed into steam. The steam severely burned both of them and seared their eyes. Neither one could fly the plane due to their burns. The transcript of their radio transmissions was tough to read.

Rich

 

I was aware of the dangers of flying after diving due to the lower air pressure, but this?? :eek: