Simple question: Overflow Tank vs. Resevoir

[CornerCarvin67]

If you're running an over flow tank.... the tank is simply there to catch and water or to allow possibly air pressure to vent from the system, correct? The water gets hot and expands. Typical radiator fill level is probably an inch or two beneath the neck of the radiator cap, correct?

The resevoir works a little different. It's more of an attempt to keep the air out of the system along with the maximum amount of water in. You typically fill the radiator comletely and the resevoir around half way full... correct?

Yes... I'm STILL battling my cooling issues. Somehow I must either still have air in the system or I have a head gasket leak. I've run both systems described above..... currently have the resevoir system.

My car continues to blow water out of the system regardless of where the fill level is on the radiator. Could I have that much air in the system or is it likely a head gasket leak is allowing air into the system and wreaking havoc?

I'm so sick and tire of this issue....

Autocrossing last Sunday was great... until the last couple of runs when the car started acting up with the above problems..

How about some FRESH perspectives??!!!!

Any good air purging ideas..... no, I don't have a heater system... so I can't splice in a filler neck. I read somewhere that a guy was loosening his temp sensor or something along those lines.

Help....

 

[Sicarius428]

You probably already did this but have your rad cap tested to see if it is actually working at the right psi.
Kevin

 

[66HertzClone]

I had a similar problem with my car. I first removed my thermostat and drilled a 1/8 hole thru the flange inside of the thermostat gasket. When I installed the thermostat again, I positioned the thermostat so this hole was at the 12 o'clock position.

Before I added coolant, I loosened the temperature sending unit a few turns. As I added coolant I watched for coolant around the threads of the sender, when it appeared I tightened up the sender. I have never had any more problems with the temp creeping higher than it should.

As for the catch can overflow tank question, look at the underside of your rad cap. If there are two rubber gaskets, one around the outside and one around the inside movable piston it is a recovery type cap. With this cap style, if the tube in your catch can, or overflow tank is submerged in coolant it will be drawn back into the radiator. If the tube from the rad into this tank is in open air there will be no coolant drawn back into the rad.

I hope this helps you out, Jeff

 

[CornerCarvin67]

The tube goes from the radiator neck to the bottom of the overflow tank.

I'm not sure what drilling the hole in the thermostat does for you? Does it allow the air from the engine to escape thru to the upper radiator hose and then out the cap?

 

[krash kendall]

This whole difference in cap thing was on my mind when I bought a new cap last month. The recovery cap has the seal on the main plunger that breaks it's seal when the spring is compressed. There is also a seal around the cap that seals it, regardless, so the coolant is directed out the spout into the overflow hose. In the centre of the main plunger you will notice an even smaller plunger that will pull ever-so slightly inwards towards the radiator to recover the collant through the top of the main plunger as a vacuum is generated due to contracting coolant. If the seal around the top cap is poor, then the rad will suck air from around it instead of pulling the coolant up the hose.

 

[LMan]

The tube goes from the radiator neck to the bottom of the overflow tank.

I'm not sure what drilling the hole in the thermostat does for you? Does it allow the air from the engine to escape thru to the upper radiator hose and then out the cap?

yes. It helps "burp" the system. Otherwise air can migrate to the engine side of the t-stat and stay there, forming a steam pocket.

 

[ForceFed70]

If it's blowing out the coolant without actually overheating (until lack of coolant causes the overheating):

It's not an "air bubble" if your blowing out coolant without overheating.

My guesses:

1) Head gasket problem.
2) "Hot spot" problem causing the coolant to boil only in a certain spot.

I'm leaning towards head gasket.
Have you tried any diagnostics yet? Compression test? Coolant system pressure/leak test?

How about that test with the large balloon or condom that I mentioned the last time you posted about your problem?

 

[CornerCarvin67]

No.. haven't tried any kind of gasket leak diagnostics.... I don't know how I guess. Anything I can try at home? Balloon test??

 

[krash kendall]

Remind us of what rad and water pump you have.

 

[CornerCarvin67]

Then what's the purpose of having a thermostat in there in the first place? The engine gets warmer... and the thermostat gradually begins to open... Isn't that the same concept? Confused....

yes. It helps "burp" the system. Otherwise air can migrate to the engine side of the t-stat and stay there, forming a steam pocket.

 

[ForceFed70]

No.. haven't tried any kind of gasket leak diagnostics.... I don't know how I guess. Anything I can try at home? Balloon test??

I would start with a compression test. You can borrow the tester from Pep boys or any place that has a "borrow a tool" program. Let us know if you don't know how to do it and we'll give you some instructions. It's pretty straight forward.

The balloon/condom test: Basically what you do is wait until your engine in nice and cool (1st thing in the morning would be perfect). Then you remove the radiator cap and place a balloon over the the spout in it's place (make sure to cover the fitting that goes to the resivoir). Once the balloon is on, start the engine and let it idle for 2-3 minutes. Basicaly just until it starts to get a little warm. If exhaust gasses are leaking past the head gasket, the balloon/condom will start to inflate.

 

[CornerCarvin67]

Krash.. I think the pump is stock... and the radiator looks like a newer, but stock model.

Yes, Nitrous... it is really odd that it's spewing without overheating.... of course when it gets to the point that the radiator is only half full... then yeah, it will start to over heat.

I'll try that balloon test....

No... I don't know how to run a compression test... I'll ask around and see if someone I know does.

Thanks for your time fellas...

 

[steel1212]

So you have to have a "special" cap to have an recovery tank work properly? I thought you just plugged a hose into the kneck on the rad and into the bottom of the recovery tank and as it cooled down it just sucked it back in due to reduced pressure? I'm getting a griffin rad and just bought a jegs polished 13# cap and their recirculating can.

This cap

This can

SORRY FOR THE HI-JACK

 

[krash kendall]

Steel, I think you would have a hard time these days finding a cap that doesn't recover.

 

[LMan]

Then what's the purpose of having a thermostat in there in the first place? The engine gets warmer... and the thermostat gradually begins to open... Isn't that the same concept? Confused....

..because the engine can be too cool as well as too hot, IOW it functions best within a narrow temp range. The t-stat recirculates the coolant/water within the block until its preset is reached (160,180,195, etc), then allows it to circulate through the radiator.

Its in the best interest to get the engine to op temp as soon as possible, which restricting the coolant flow helps to do. A 'cold' engine runs more poorly, emits more pollutants, can foul the oil, etc.

 

[krash kendall]

Just remember, the rating on your thermastat sets your engine's minimum operating temperature, not maximum.

 

[ForceFed70]

To do a compression test:

1) Pull out all spark plugs.
2) Remove coil wire
3) Thread compression tester into spark plug hole.
4) Crank engine for 10-15 seconds then take a look at the pressure reading on the guage.
5) Reset guage and Repeat test for each cylinder. (write down the pressure readings)

The pressure readings you get will depend on cranking speed, valve and ring seals, compression ratio, etc. The actual pressure isn't all that important. What's important is that the pressures across all 8cyln are roughly the same (within 20%).

If 1 or 2 cyln are lower than the others then this points to a problem with those particular cylinders. (could be head gasket, rings, or valve seals.

 

[Tim65GT]

When doing a compression test, I think I remember something about having the throttle wide open.

Anyone back me up?

 

[ForceFed70]

When doing a compression test, I think I remember something about having the throttle wide open.

Anyone back me up?

While keeping the throttle open may show slightly higher compression pressures, like I stated above...the actual pressure isn't all that important. What's important is that all cylinders measure roughly the same.

So it really doesn't matter so long as you are consistant in your measurements.

 

[HistoricMustang]

If you're running an over flow tank.... the tank is simply there to catch and water or to allow possibly air pressure to vent from the system, correct? The water gets hot and expands. Typical radiator fill level is probably an inch or two beneath the neck of the radiator cap, correct?

The resevoir works a little different. It's more of an attempt to keep the air out of the system along with the maximum amount of water in. You typically fill the radiator comletely and the resevoir around half way full... correct?

Yes... I'm STILL battling my cooling issues. Somehow I must either still have air in the system or I have a head gasket leak. I've run both systems described above..... currently have the resevoir system.

My car continues to blow water out of the system regardless of where the fill level is on the radiator. Could I have that much air in the system or is it likely a head gasket leak is allowing air into the system and wreaking havoc?

I'm so sick and tire of this issue....

Autocrossing last Sunday was great... until the last couple of runs when the car started acting up with the above problems..

How about some FRESH perspectives??!!!!

Any good air purging ideas..... no, I don't have a heater system... so I can't splice in a filler neck. I read somewhere that a guy was loosening his temp sensor or something along those lines.

Help....

Am headed out but believe I have a solution. Will put it up tomorrow.

HistoricMustang
www.historicmustang.com