radiator & overflow tank questions
11-06-13, 10:42 AM
#1
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radiator & overflow tank questions
Year: 87
Model: Turbo II
Specifics: 5lug & 5spd
recently i overheated the motor and had to limp it home with lots of stops and refills of the radiator. the heater core hose let go on the block and let all the coolant out.
as such ive been a little paranoid of the whole cooling system so i check it incessantly. The car hasnt been driven more than 5 miles since it happened and i have replaced the hose.
heres the question: when i let the car sit overnight and then pull off the rad cap i noticed that they coolant level is lower than where i filled it to. basically i filled it to the brim and the tossed the rad cap on it. well last night i filled it to the brim and watched the coolant level drop like 2 inches then stop. then i filled it and watched it happen again. i did this like 6-8 times while listening for drips, trickles or any sign that they can was having a problem. what i found was, the coolant was going directly into the overflow tank at the front of the car.
what exactly does that second radiator cap do? i THOUGHT it would act as the main rad cap releasing pressure into the overflow tank since there is no relief at the filler neck. why would the coolant, under no pressure other than a few inches of difference in height (engineers call this feet of head............ok stop laughing, focus) drip into the overflow tank like that?
is that a sign that i need to replace that secondary cap? if so what pressure should that cap be rated at? i didnt see it listed on the cap and it normally is.
Model: Turbo II
Specifics: 5lug & 5spd
recently i overheated the motor and had to limp it home with lots of stops and refills of the radiator. the heater core hose let go on the block and let all the coolant out.
as such ive been a little paranoid of the whole cooling system so i check it incessantly. The car hasnt been driven more than 5 miles since it happened and i have replaced the hose.
heres the question: when i let the car sit overnight and then pull off the rad cap i noticed that they coolant level is lower than where i filled it to. basically i filled it to the brim and the tossed the rad cap on it. well last night i filled it to the brim and watched the coolant level drop like 2 inches then stop. then i filled it and watched it happen again. i did this like 6-8 times while listening for drips, trickles or any sign that they can was having a problem. what i found was, the coolant was going directly into the overflow tank at the front of the car.
what exactly does that second radiator cap do? i THOUGHT it would act as the main rad cap releasing pressure into the overflow tank since there is no relief at the filler neck. why would the coolant, under no pressure other than a few inches of difference in height (engineers call this feet of head............ok stop laughing, focus) drip into the overflow tank like that?
is that a sign that i need to replace that secondary cap? if so what pressure should that cap be rated at? i didnt see it listed on the cap and it normally is.
11-07-13, 02:38 PM
#3
Have you started it yet? If so did it smoke like a chimney?
The coolant rings don't like overheating, at all.
Or, you may be getting lucky and the bubbles in the system are working out of it.
The rad cap ON the rad is just to fill the rad, usually you never have to worry about it cause its easier to fill from the t-stat housing
I would make sure its full on freeze and fire if up with the t-stat cap off and let it idle and see if it over heats or smokes like crazy. If it runs for a bit than starts gushing coolant out, rebuild time is probably in your future
The coolant rings don't like overheating, at all.
Or, you may be getting lucky and the bubbles in the system are working out of it.
The rad cap ON the rad is just to fill the rad, usually you never have to worry about it cause its easier to fill from the t-stat housing
I would make sure its full on freeze and fire if up with the t-stat cap off and let it idle and see if it over heats or smokes like crazy. If it runs for a bit than starts gushing coolant out, rebuild time is probably in your future
11-07-13, 03:07 PM
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getting 0 of that. i presume that it will gush or bubble on start just like any other car with a blown head gasket. I got absolutely 0 bubbles in the coolant. i think i got mega lucky.
11-07-13, 03:52 PM
#5
I'm a FD owner, but since you haven't had some of the others respond I'll give it a shot........
By your description you've seriously over-heated. Coolant seals CAN degrade quickly at temperatures over about 240 F. Do that and you CAN get symptoms like your describing... i.e. unexplained coolant loss without a puddle under the car. In an intact system, as coolant heats up in a running engine, it expands and flows into the overflow tank. When you shut down and the engine and coolant cool, a natural vacuum should draw that coolant back out of the overflow and into the engine. That's if there are no leaks and the system is full.
I recommend you do the following:
*Open the overflow tank and fill it to the indicated level. Replace the cap and closely inspect the hose leading to the tank for any obstructions or kinks.
*Replace any questionable hoses and inspect clamps. Get a good light and look for anything remotely damp or sweating. To the extent you can, make damn sure nothing is leaking.
*Open the filler neck, fill it with coolant, replace the cap and squeeze the upper radiator hose 4 or 5 times. Remove the cap, refill and repeat until it won't take any more coolant.
*Get new caps. I THINK the spring cap should be ~ 13 psi cap (or .9 bar).
Drive the car, get it up to full operating temperature and then let it cool completely. When you pull off the new cap, there SHOULD be a slight vacuum that you can feel when you pull it off and the level should be just below the overflow hose nipple.
If the symptoms you describe persist, have the cooling system pressure tested. I think most chain parts stores will loan (with a deposit) a pressure tester with the correct cap to fit. If it fails you may have a failed coolant seal. some other symtoms of a failed coolant seal may be a lumpy idle on cold start, steam (white smoke) at the tail pipe on cold start with a vaguely sweet smelling exhaust. A test can also be done on the coolant for hydrocarbons.
By your description you've seriously over-heated. Coolant seals CAN degrade quickly at temperatures over about 240 F. Do that and you CAN get symptoms like your describing... i.e. unexplained coolant loss without a puddle under the car. In an intact system, as coolant heats up in a running engine, it expands and flows into the overflow tank. When you shut down and the engine and coolant cool, a natural vacuum should draw that coolant back out of the overflow and into the engine. That's if there are no leaks and the system is full.
I recommend you do the following:
*Open the overflow tank and fill it to the indicated level. Replace the cap and closely inspect the hose leading to the tank for any obstructions or kinks.
*Replace any questionable hoses and inspect clamps. Get a good light and look for anything remotely damp or sweating. To the extent you can, make damn sure nothing is leaking.
*Open the filler neck, fill it with coolant, replace the cap and squeeze the upper radiator hose 4 or 5 times. Remove the cap, refill and repeat until it won't take any more coolant.
*Get new caps. I THINK the spring cap should be ~ 13 psi cap (or .9 bar).
Drive the car, get it up to full operating temperature and then let it cool completely. When you pull off the new cap, there SHOULD be a slight vacuum that you can feel when you pull it off and the level should be just below the overflow hose nipple.
If the symptoms you describe persist, have the cooling system pressure tested. I think most chain parts stores will loan (with a deposit) a pressure tester with the correct cap to fit. If it fails you may have a failed coolant seal. some other symtoms of a failed coolant seal may be a lumpy idle on cold start, steam (white smoke) at the tail pipe on cold start with a vaguely sweet smelling exhaust. A test can also be done on the coolant for hydrocarbons.
11-07-13, 05:00 PM
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i think i need to elaborate here. because ive basically done all that.
I filled the cooling system and bled it as best i could then hit it with a pressure tester. at about 12lbs of pressure i heard this big rush that kind of sounded like a toilet flushing in the distance. it turns out that this was the radcap by the headlight opening and letting a bunch of coolant into the overflow tank.
Ive driven the car a hand full of times around the block under boost and id think that an overheating/lost coolant situation were present it would have already become apparent. I get 0 overheating, in fact the gauge reads like the bottom 1/4 the entire time which may or may not be accurate.
with the motor over-night cold i topped off the cooling system at the filler neck just above the thermostat housing. The coolant was not disappearing, its going into the overflow tank but just at a trickle.
this part is important to understand....if you take a hose full of water and bend it in a U shape the water will be equal height in either side of the hose unless one side is pressurized somehow.
when i added coolant at the filler neck and took off the overflow tank lid and turned the normally downward pointing hose upwards, the draining into the overflow tank stopped as i equalized the height of the coolant in the system. i THINK that i managed to get the second rad cap, the one by the headlight stuck open somehow and i think a replacement cap would do just fine...
OR now that i think about it, the caps are reversed. the one with a pressure rating needs to be next to the overflow tank and the one with no pressure rating, needs to be on the filler neck by the t-stat housing. i rationalize this with the thought, even if the cap on the t-stat neck had a relief pressure theres nowhere for the coolant to go since theres no hoses from it to any overflow tank.
thoughts on flipping the caps?
I filled the cooling system and bled it as best i could then hit it with a pressure tester. at about 12lbs of pressure i heard this big rush that kind of sounded like a toilet flushing in the distance. it turns out that this was the radcap by the headlight opening and letting a bunch of coolant into the overflow tank.
Ive driven the car a hand full of times around the block under boost and id think that an overheating/lost coolant situation were present it would have already become apparent. I get 0 overheating, in fact the gauge reads like the bottom 1/4 the entire time which may or may not be accurate.
with the motor over-night cold i topped off the cooling system at the filler neck just above the thermostat housing. The coolant was not disappearing, its going into the overflow tank but just at a trickle.
this part is important to understand....if you take a hose full of water and bend it in a U shape the water will be equal height in either side of the hose unless one side is pressurized somehow.
when i added coolant at the filler neck and took off the overflow tank lid and turned the normally downward pointing hose upwards, the draining into the overflow tank stopped as i equalized the height of the coolant in the system. i THINK that i managed to get the second rad cap, the one by the headlight stuck open somehow and i think a replacement cap would do just fine...
OR now that i think about it, the caps are reversed. the one with a pressure rating needs to be next to the overflow tank and the one with no pressure rating, needs to be on the filler neck by the t-stat housing. i rationalize this with the thought, even if the cap on the t-stat neck had a relief pressure theres nowhere for the coolant to go since theres no hoses from it to any overflow tank.
thoughts on flipping the caps?
11-07-13, 05:40 PM
#7
...OR now that i think about it, the caps are reversed. the one with a pressure rating needs to be next to the overflow tank and the one with no pressure rating, needs to be on the filler neck by the t-stat housing. i rationalize this with the thought, even if the cap on the t-stat neck had a relief pressure theres nowhere for the coolant to go since theres no hoses from it to any overflow tank.
thoughts on flipping the caps?
thoughts on flipping the caps?
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