bleeding cooling system!

[geoff]

what more can I do !
I drilled a hole in the themostat. I cut the heater hose and put a bleeder valve at the topmost position.
Every time I go out in the car it overheats and I can bleed off air. The expansion tank then fills up.
The bottom hose remains cold and although the thermostat is very hot - it seems not to open.
I am at a loss. Perhaps the themostat is siezed, or there is air in the bottom hose - or it is drawing air in somehow?
any ideas very welcome
thanks
geoff

[kilrwail]

Maybe you have the thermostat in backwards.

[RRoller123]

Make sure that the coolant T at the top front of the engine is in the right orientation. One side is restricted, and it can be installed either way around.

[geoff]

to be honest, I don't think so - but right now I am prepared to try anything.
What I can't understand is :
1) two of the hoses to the t'stat and the stat itself are bery hot (although the bottom hose is cold) so why does the stat not open if it is surrounded by all this heat?
2) why does the level of coolant in the expansion tank keep rising after each time I bleed off the air at my heater T piece?

[zachmac]

to be honest, I don't think so - but right now I am prepared to try anything.
What I can't understand is :
1) two of the hoses to the t'stat and the stat itself are bery hot (although the bottom hose is cold) so why does the stat not open if it is surrounded by all this heat?
2) why does the level of coolant in the expansion tank keep rising after each time I bleed off the air at my heater T piece?

1) Sounds like a bad thermostat OR you are heating it with steam which I am not sure will cause it to open? As posted above, make sure you have it hooked up to the hoses correctly. Since you obviously have air in the system no reason not to just pull the thermostat and boil it on the stove in a pan of water (thermostat covered) to make sure it is opening. Use a thermometer in the water to see what temp it opens up at.

2) If you are venting the system when hot you are also depressurizing it. As pressure drops so does the saturation temperature (boiling point). Once you drop the pressure / sat temp below the system actual temp it flashes to steam pushing water out to your expansion tank. BUT, this would all mean that the fluid is escaping the radiator through the cap to the expansion tank at a relatively low pressure, something that shouldn't occur. The radiator cap is supposed to only relieve pressure above a certain pressure, thereby normally maintaining the system pressure high so Tsat is well above the actual system temperature. Basically you are trying to keep the system pressurized so it can run above 212 degrees without boiling (hot water transfers heat well, steam is basically an insulator).

Based on what you describe I'd suspect a faulty radiator cap. Cheap and easy to replace and see. If it is not maintaining system pressure then you are operating at too low a pressure and boiling the fluid.

[RRoller123]

can you post a pic of the t-stat housing installation? It is possible to put them in incorrectly, and still have it look like the right way.

[MattVAS]

I wrote up a nice burping thing several years ago.
It covers which way the thermostat needs to go and how I personally burp the cars.

NOTE: Drilling holes in the thermostat really aren't the answer. The air is in the head not at the thermostat. There isn't a water/air seal on the thermostat so time or some good squeezing on the lower hose resolves air on that end. Really it is almost always air in the head or thermostat in bacwards.

---- How-to ------

At Vick Auto, we have the fix. A coolant burp/flush kit for Fiat 124 (Spider, Coupe, etc.) is the best answer to the pesky air bubble issue in a Fiat 124.

As you can see in the picture, the burp/flush kit is easily installed in the upper heater hose that passes over the exhaust cam. At Vick Auto, we try to have these in stock at all times as it is the best way to get rid of air in the coolant system. Our instructions for filling your coolant system with one of these kits are as follows...

- Install burp/flush kit
- Open heater valve to ensure coolant fills the heater core
- With the caps off of the burp/flush kit AND the radiator, begin filling the system from the radiator cap
- Once you can no longer fill into the radiator directly, move to the burp kit cap and begin filling from there. DO NOT PUT THE CAP ON THE RADIATOR, YET
- You will see bubbles and some fluid poor out of the radiator, this is to be expected. Once the bubbles stop, put the cap on the radiator. DO NOT CAP THE burp kit
- Fill more into the burp kit while slowly and gently squeezing the upper radiator hoses. This is to help suck fluid into the cylinder head
- When no more fluid can go into the burp kit, place the cap on it
-Now that all the caps are in place squeeze the lower radiator to thermostat hose rapidly and hard about a dozen times. This is to disperse and clear out any air bubbles at the thermostat or just in the lower motor
- Open the cap on the burp kit once again you may see it is empty, that is to be expected. Simply fill it up until it can take no more while gently squeezing the upper radiator hoses
- You should almost be done! DO NOT GO FOR A JOY RIDE YET
- Start your car and let it reach operating temperature to ensure that the fan comes on once the motor is warm. Be aware some water temp sensors and dash gauges may actually be wrong (as much as +/-30 degrees!). A good infrared thermostat is a wise investment to get accurate temps
- IF YOUR FAN NEVER COMES ON AND THE CAR BEGINS TO OVERHEAT, SHUT DOWN IMMEDIATELY. This means you have a failure of either the fan, fan switch, thermostat, or an air bubble in the system. If you have just replaced the thermostat and the fan switch you can almost certainly rule those out

I hope this walk-through and the pointers above will help everyone have a safe and easy thermostat swap in the future. If you have not picked up new parts yet, you may want to do this before you start. At the Vick Auto shop, we carry everything you need.

Remember, the faster you get a job finished, the better your chances of failure may be.

Matt

-----------------------



Hopefully all that can also help.

[RRoller123]

Excellent, Matt! That pic should help resolve that question, they are remarkably symmetric, and they can be installed incorrectly, as can the T up front. Fraught with opportunity for error!

[geoff]

thanks all for the inputs. Seems that my stat is not working. Does not seem to do anything when submerged in boiling water so I now have another on order. Yes, I agree that it is indeed easy to instal it the wrong way.
Not so sure about the T piece though - if you installed that the wrong way the bleed screw would not be at the top !

[RRoller123]

The temp sensor and bleed screw holes are tapped exactly the same, so it can be put on backwards and still have the sensor and bleed screw in the right location.

[geoff]

Vic posted a good clear picture of the orientation of the stat and thanks for that. However, it shows the 'wax' part of the stat situated at the bottom hose connection and as this actuates the opening of the stat, I would have expected that to be nearest the engine, i.e. the water pump hose?

[RRoller123]

This might help

[Spider951]

I bleed the coolant system of trapped air by first topping up everything with coolant; then start car and heat up system to open up thermostat; then slowly open valve spliced into bypass hose in heater loop at rear of engine bay ( bypassses the heater - my heater core was shot anyway ). Only open the valve just enough to let out some bubbles of air/coolant (a bit messy so have rags handy around valve to mop up the minor mess); close valve; refill overflow tank (assuming fluid level dropped). Repeat the procedure until no more drop in coolant; it takes 2-3 rounds to get 'er done. Test drive to make sure; repeat if necessary. (Of course this "hack" means no heater - not major big deal here in the deep South USA; I may have to do it "by the book" if I ever replace the heater core).

[vdesigner99]

I had the same problem a couple of years ago.
Turned out to be the radiator cap.
See my explanation:
http://www.fiatspider.com/f15/viewtopic ... 2&start=15

Victor

[geoff]

thanks all for the input.
I am still a little confused however - both the photo and diagram above show that the stat is positioned with the 'wax' actuator port connected to the bottom hose. This means that the coolant must pass through the radiator and out of the bottom hose before reaching the actuator of the stat. Am I missing something here?