Another cooling system question

[dlowe01]

Was wondering if the overflow tank is supposed to have any kind of whole in it so that preasure can come out????? My radiator cap keeps puicking out coolant. The car stays around 180 on the highway but climbs up to 200 to 210 in traffic. Why I'm at it, what is the proper procedure to burp the system to get out all the air and could air in the system be causing the puicking through the radiator cap?

[Back in Black]

This will allow the air in the block to escape. If you are having heat problems, go with 1 or 2 bottles of Water Wetter and the rest, distilled water only. Make sure not to use this mix if there is ANY chance of freezing conditions!!!

[CRZN427]

If you have the old Ford expansion tank, the one that mounts on the thermostat housing, there should be no holes in it that weren't put there by Ford. That is, a fill spigot with overflow, the outlet at the thermostat and the inlet from the top radiator hose.

That tank has a horrizontal baffel with a hole in it just below the cap opening. That hole, in the baffel, is the fill line for this tank.

Obviously you want all the air out of the rest of the system and a good mixture of coolant in the system.

My experience in getting the air out is to fill and burp as much as possible cold, then drive it, let it cool and check the level. This may have to be done several times.

The thermostats I have seen have enough bypass that an additional hole does not help in bleeding air out of the block.

A 50/50 mixture of antifreeze works best in that it gives optimum freeze protection as well as the best heat capacity increase over plain water.

The system should have an overflow line coming off the fill cap spigot on the expansion tank. The "radiator cap" there should be good for around 16 psi. Check the specs of the donor car and /or an informed engine builder / tuner to determine if that is enough for a modified engine.

If you have a cap on the radiator as well, it should have a pressure rating that is equal to, or slightly higher than, the one on the expansion tank. There will probably be an over flow tube on this spigot as well.

To the best of my knowledge, these overflow tubes won't work with a recovery system. The stock radiator cap on the old Fords was for over pressure relief only. There is no way the system can draw fluid back through these caps since thy are designed to hold everything in up to their "pop" pressure, at which point the fluid goes out the end of the over flow tube to the ground.

The tank itself is designed to contain the expanded water from the hot block with no loss of fluid, hense the name "expansion tank".

A severe over heat situation will cause the pressure cap to let fluid escape to accomidate the additional volume of fluid expansion due to the higher than normal temperature in the engine.

The space above the hole in the baffel is calculated, by the Ford designers, to hold the increase in volume of the normally hot water, don't put any aditional fluid there or it will pe pushed out as soon and the block starts to heat up.

If you are loosing water at normal engine operating temperatures the pressure cap may be bad, or another system leak may be present.

If the water temperature is always extremely hot after slow speed driving, the radiator may not be big enough, the water flow may not be sufficient (due to the pump or clogged radiator) the air flow may not be sufficient to extract the heat from the radiator of a combination of all these things.

A good friend found that the three core radiator (with large oval cores) worked better than the four core he took out.

I have seen some fan installations that inhibit good air flow as well.

Look at the size of the fan the old Fords had on the stock installation, the size of the radiator and the volume of air that was drawn through when the, engine driven, fan clutch engaged.

If you are not moving that much air through that much water you will probably have a heat problem.

[vettestr]

LONG WINDED but covers questions and problems I have seen here many times. There are many ways to skin a cat but think this is a good baseline.
A coolant system should have the following attributes to allow trouble free operation and should be a closed system. The engine coolant should be able to reach and maintain a minimum of 12 psi to maximize heat transfer. A radiator cap should be located at the highest point of the system to allow coolant to be added. A radiator cap and system must be capable of remaining sealed until pressure is above average system pressure by about 15%. The coolant must reach 12 PSI to reach maximum efficiency but too high of a pressures will exceed other abilities of average stock components like the gaskets sealing coolants and soft plugs or freeze plugs. I would say 20 psi is max for average stock engines. 20 PSI can be exceeded in racing preped engines and those with higher quality intake and head gaskets but I am trying to describe stock or average conditions. To make sure maximum safe pressures are not exceeded a release pressure is preset/built into the radiator cap from 14 to about 18 PSI depending what you buy. When this pre-determined max level is reached the cap relieves pressure and fluid from coolant system dumps (into a recovery tank or expansion tank to be sucked back into engine as it cools.
Radiator can be mounted lower than engine but will need a way to add coolant to system at a level higher than system (engine and rad.) this is usually a remote expansion tank. The expansion tank must be plumbed so that the in and out hose back to system is covered with coolant or in the bottom of tank so air is not drawn back into and mixed with coolant in the engine. Tank can have air in top of tank for expansion but can not get mixed with circulating coolant. The remote expansion tank needs a Rad. cap so it can relieve max pressure if needed but air gap on top will compress unlike fluid to allow cold to hot volume changes. If capacities are correct you do not need a recovery tank on the expansion tank. I recomend an 18 psi cap on your tank. 20/ 23 or more PSI if a must and only if everything is built to hold high presures. Pressures this high are a fix or trade off to other limitations in the system.
If engine gets hot while at cruise your system is too small. If it only gets hot when in stop and go your system may be marginal size but lacks enough air flow to work and need more air flow and/or ways to expell heat like Oil coolers and more fans. All this assumes there are no Engine or outside problems causing the symptoms of overheating.