Coolant Loss

[HamanaRob]

66FJ40 all stock F motor. My problem is coolant loss. Coolant keeps comming out the overflow hose utill its to low to cool.
Usually about 75 miles. I've installed an overflow tank and all it does is fill up and flow out of that. It runs fine and cool untill the level drops. no steam or other leaks.
Any thoughts? Thanks

 

[Joseph Siri]

does it overheat?


or just keep getting low untill then it overheats?

 

[HamanaRob]

Just keeps getting low until it overheats

 

[FF LC FREAK]

Do you have the right radiator cap? It should only allow coolant into the overflow when it heats up above a certain point creating pressure in the system. That is why you have a pressure rated cap. I believe stock is 13 pounds. Make sure yours is working and also that it covers the overflow tube opening when cool. Or, just to make sure, buy a new one and try it. They are pretty cheap.

Good luck!

 

[antFJ]

something is blocking flow is my guess...

once the thermostat opens the engine pulls coolant from the rest of the system and if the lines or radiator are blocked by something then the coolant has to go somewhere... aka out the overflow bottle.

take it back - what is above sounds better

 

[spdwaver]

something is blocking flow is my guess...

once the thermostat opens the engine pulls coolant from the rest of the system and if the lines or radiator are blocked by something then the coolant has to go somewhere... aka out the overflow bottle.

take it back - what is above sounds better

I was thinking that maybe the thermostat may not be opening at the rated temperature. One way to check this is to remove the thermostat and put it in water on the stove, turn on the burner. Get a (turkey/meat?) thermometer to check the progress; watch for the opening and measure the temperature at which it opens.

 

[HamanaRob]

I should have mentioned I have installed a new thermostat(checked it on stove first) and its a new cap.

 

[splitshot]

Does your coolant smell like combustion gases?

 

[dgangle]

I see one of these in your future

Cooling System Pressure Tester

 

[bsevans]

I see one of these in your future

Cooling System Pressure Tester

I think that before I invested in the pressure test kit above, I would invest in the following Combustion Leak Detector Kit made by Lisle.

Combustion Leak Detector Kit

 

[dgangle]

I think that before I invested in the pressure test kit above, I would invest in the following Combustion Leak Detector Kit made by Lisle.

Combustion Leak Detector Kit

Yea, that's kinda neat but looks like a hassle. "...Place tapered end of tool into radiator opening after draining of some coolant...Includes leak detector and testing fluid..."
Plus the fluid appears to be a consumable. Another jug of chemicals laying around and trying to source some more XXX years later when it's gone/can't find it and one doesn't remember where you bought it.

Looks like a neat little imediate means-to-an-end and the price is certianly attractive but anybody serious about cooling system diagnostics needs to have a pressure test kit, right along with a battery charger and battery load tester/charging system analyzer.

Not trying to be a dick or anything...please don't take it as that. ...just might be the trick he needs.

 

[bsevans]

Yea, that's kinda neat but looks like a hassle. "...Place tapered end of tool into radiator opening after draining of some coolant...Includes leak detector and testing fluid..."
Plus the fluid appears to be a consumable. Another jug of chemicals laying around and trying to source some more XXX years later when it's gone/can't find it and one doesn't remember where you bought it.

Looks like a neat little imediate means-to-an-end and the price is certianly attractive but anybody serious about cooling system diagnostics needs to have a pressure test kit, right along with a battery charger and battery load tester/charging system analyzer.

Not trying to be a dick or anything...please don't take it as that. ...just might be the trick he needs.

Gee, I'm sorry, but the Stant 12270 does a pressure test of the coolant system and caps only. It does not have the capability to test for combustible gases in the coolant, which would be the first thing I would want to eliminate.
I own this tester and it comes with enough testing fluid that the average mechanic can do numerous tests. One test of the coolant system tells you whether your problem is combustible leakage or coolant system hardware issues. I stand by my recommendation.