No AST or overflow tank?
No AST or overflow tank?
my friends single turbo fd has no ast or overflow tank...
theres a 3/8 hose going from the nipple near radiator cap to the bottom of the radiator. will this cause any problems? its been like this for a year
theres a 3/8 hose going from the nipple near radiator cap to the bottom of the radiator. will this cause any problems? its been like this for a year
Is the car running coolant or something like Evans? The problem with not using an overflow tank is that the coolant has no where to go when it expands. It will cause a lot of unneeded stress on the coolant lines and could possibly cause a hose to weaken and burst over time.
With the overflow hose going straight to the bottom of the radiator that cooling system there is no pressure relief and will build up some serious pressure. Get an AST on that car or put the FC filler neck with pressure cap on and route properly to the overflow.
Full Member
Joined: Jan 2003
Posts: 222
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From: Gardena, CA
It's not just a coolant hose that can fail due to excessive pressure, but the major concern is that it would put excessive pressure on the internal water seals..... not as easy to replace as a coolant hose.
The radiator cap regulates the cooling system pressure by opening up to the overflow res when it reaches the designated pressure. Stock is .9 bar or approximately 13lbs. By overflowing back into the radiator, pressures would go way higher than that. You need to route that hose to an AST and then to an overflow res. This is all assuming that your friend's FD is running a mix of Ethylene Glycol and Water.....
First thing to check is what he has in the cooling system, if it is something like Evans NPG, than it's a little different. Evans NPG has an operating pressure of 0 to 7 lbs so it would never even reach the point where it would need an overflow res.
The radiator cap regulates the cooling system pressure by opening up to the overflow res when it reaches the designated pressure. Stock is .9 bar or approximately 13lbs. By overflowing back into the radiator, pressures would go way higher than that. You need to route that hose to an AST and then to an overflow res. This is all assuming that your friend's FD is running a mix of Ethylene Glycol and Water.....
First thing to check is what he has in the cooling system, if it is something like Evans NPG, than it's a little different. Evans NPG has an operating pressure of 0 to 7 lbs so it would never even reach the point where it would need an overflow res.
Racecar - Formula 2000
Joined: Sep 2002
Posts: 4,033
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From: Bath, OH
My worry would not be pressure build-up, assuming the fill opening has a standard 0.9 BAR (13 psi) pressure-relief cap. My worry would be expanding coolant escaping, and then having none to draw back, causing overheaing due to air pockets in the engine.
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well theres one problem were the radiator cap is theres soppoused to be two nipples. like i saw on the link from mahjik but on my friends rx7 theres only one nipple. then lower one.
so from what i read on the link im gonna run a hose from the top of the overflow to the nipple under the cap and one from the bottom of the overflow to the bottom of the radiator??
so from what i read on the link im gonna run a hose from the top of the overflow to the nipple under the cap and one from the bottom of the overflow to the bottom of the radiator??
Basically yes. BUT! You need a filler neck on the FD which is removable (to use an FC filler neck). Mazda changed the design later so the filler necks were one piece with the t-stat housing.
thats what i have a one piece on the thermostat housing. so block off the nipple at the bottom of the radiator and run a hose from the bottom of the overflow to the nipple at the t stat housing?
You should put back the AST then or find an older style thermostat housing that is 2-piece to eliminate the AST properly.
Only if you have the two piece water filler neck which it appears you do not. You can NOT delete it unless you ahve the two piece filler neck or get creative with tapping somethign in that is higher than the spring cap which at that point you would be better off buying a used filler neck that is two piece. For now, just put the ast back on.
To the OP, you need to have the spring type relief cap either on your AST or your filler neck (if you have the FC filler neck top piece with the pressure relief cap) routed to your overflow tank, otherwise there may be excessive pressure in the cooling system, if you're running standard water/coolant that could be a problem as others have said.
I eliminated my AST about a month ago, have put around 500 miles on the car so far with ambient temps in the 70-100* F range, all types of driving conditions (freeway, traffic, city streets, boosting, etc.). My water temps have not changed at all, from what I can tell. They are something like 83-85* F on the freeway when it's cooler outside (< 80* F) and creep up to 88* F in traffic. Last weekend it was 103* where I was and I was around 93* F when stuck in traffic. I have the FC filler neck with the pressure relief cap of 0.9 bar (~13 psi), and the filler neck is routed to my overflow tank, and the hose on the thermostat housing is routed to the bottom of the radiator. My overflow tank is topped off and the filler neck water level is too.... took about two weeks and three or four short trips to top off the filler neck after the AST delete.
One thing I don't understand is how coolant itself can really expand (it does, but not as much as a solid or especially a gas would for the same increase in temperature, everything else being equal), the "expansion" everyone seems to talk about is probably mostly due to the volume expansion due to increased temperature of the bubbles mixed in with the coolant.
I eliminated my AST about a month ago, have put around 500 miles on the car so far with ambient temps in the 70-100* F range, all types of driving conditions (freeway, traffic, city streets, boosting, etc.). My water temps have not changed at all, from what I can tell. They are something like 83-85* F on the freeway when it's cooler outside (< 80* F) and creep up to 88* F in traffic. Last weekend it was 103* where I was and I was around 93* F when stuck in traffic. I have the FC filler neck with the pressure relief cap of 0.9 bar (~13 psi), and the filler neck is routed to my overflow tank, and the hose on the thermostat housing is routed to the bottom of the radiator. My overflow tank is topped off and the filler neck water level is too.... took about two weeks and three or four short trips to top off the filler neck after the AST delete.
One thing I don't understand is how coolant itself can really expand (it does, but not as much as a solid or especially a gas would for the same increase in temperature, everything else being equal), the "expansion" everyone seems to talk about is probably mostly due to the volume expansion due to increased temperature of the bubbles mixed in with the coolant.
To the OP, you need to have the spring type relief cap either on your AST or your filler neck (if you have the FC filler neck top piece with the pressure relief cap) routed to your overflow tank, otherwise there may be excessive pressure in the cooling system, if you're running standard water/coolant that could be a problem as others have said.
I eliminated my AST about a month ago, have put around 500 miles on the car so far with ambient temps in the 70-100* F range, all types of driving conditions (freeway, traffic, city streets, boosting, etc.). My water temps have not changed at all, from what I can tell. They are something like 83-85* F on the freeway when it's cooler outside (< 80* F) and creep up to 88* F in traffic. Last weekend it was 103* where I was and I was around 93* F when stuck in traffic. I have the FC filler neck with the pressure relief cap of 0.9 bar (~13 psi), and the filler neck is routed to my overflow tank, and the hose on the thermostat housing is routed to the bottom of the radiator. My overflow tank is topped off and the filler neck water level is too.... took about two weeks and three or four short trips to top off the filler neck after the AST delete.
One thing I don't understand is how coolant itself can really expand (it does, but not as much as a solid or especially a gas would for the same increase in temperature, everything else being equal), the "expansion" everyone seems to talk about is probably mostly due to the volume expansion due to increased temperature of the bubbles mixed in with the coolant.
I eliminated my AST about a month ago, have put around 500 miles on the car so far with ambient temps in the 70-100* F range, all types of driving conditions (freeway, traffic, city streets, boosting, etc.). My water temps have not changed at all, from what I can tell. They are something like 83-85* F on the freeway when it's cooler outside (< 80* F) and creep up to 88* F in traffic. Last weekend it was 103* where I was and I was around 93* F when stuck in traffic. I have the FC filler neck with the pressure relief cap of 0.9 bar (~13 psi), and the filler neck is routed to my overflow tank, and the hose on the thermostat housing is routed to the bottom of the radiator. My overflow tank is topped off and the filler neck water level is too.... took about two weeks and three or four short trips to top off the filler neck after the AST delete.
One thing I don't understand is how coolant itself can really expand (it does, but not as much as a solid or especially a gas would for the same increase in temperature, everything else being equal), the "expansion" everyone seems to talk about is probably mostly due to the volume expansion due to increased temperature of the bubbles mixed in with the coolant.
86-88 Cap Assembly w/overflow tube
http://www.mazdatrix.com/b8.htm
