What psi radiator cap do you use?
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Joined: Aug 2011
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From: North Dakota
What psi radiator cap do you use?
Hey guy's i'm just wondering what kind of radiator cap everyone use's. If yall could just post the brand and psi/kpa that would be great so i can see what is more common. At the moment i am running a cheap O'reillys 13psi and i think a higher one to keep my coolant from boiling. Other than what seems to be just a too low pressure radiator cap my car runs and cools perfectly i just think i need to raise my boiling point with a better radiator cap. Let me know what yall think!
Joined: Oct 2003
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From: Norcal/Bay Area, CA
I use a .9 bar (13 psi) stock cap. Seems to work for the majority of people. I don't see why you 'need' to change something on a car that "runs and cools perfectly". Is there some other problem you are trying to fix?
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From: North Dakota
The problem i have is very strange, the coolant temp guage in the car reads very low temperatures approx. 1/4-1/3 above the C. It really never goes above 1/3 of the way because i have a good flow of air through the radiator... yet it still will boil it out.
talking head
Joined: Apr 2008
Posts: 2,775
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From: Perth, WA, OZ
i have used 1.3 bar and currently use 1.1 bar ( summer ambient is beyond 100 F )
s4.5 hybrid engines
the 1.3 bar led to a fail of the coolant jacket on one engine
( truth be told it wasn't the best plate there already,, and i was using viton coolant O rings , and it lasted a fair while and was taken out on a very hot day )
[ btw the viton ring stayed intact ! ]
in oz,, where propylene glycol is not easy to find ,, and temps can be "excessive" then the 1.1 and 1.3 bar caps are the way to go
( provided the engine cooling system is maintained and healthy )
you guys do know that the FD initially came with the high pressure systems,, and dealers retrofitted the 0.9 bar stuff due to factory bulletins
( obviously concerned about the coolant seal wall issues ,, FD pates can be very thin cooling seal walls compared to s4/5 )
s4.5 hybrid engines
the 1.3 bar led to a fail of the coolant jacket on one engine
( truth be told it wasn't the best plate there already,, and i was using viton coolant O rings , and it lasted a fair while and was taken out on a very hot day )
[ btw the viton ring stayed intact ! ]
in oz,, where propylene glycol is not easy to find ,, and temps can be "excessive" then the 1.1 and 1.3 bar caps are the way to go
( provided the engine cooling system is maintained and healthy )
you guys do know that the FD initially came with the high pressure systems,, and dealers retrofitted the 0.9 bar stuff due to factory bulletins
( obviously concerned about the coolant seal wall issues ,, FD pates can be very thin cooling seal walls compared to s4/5 )
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talking head
Joined: Apr 2008
Posts: 2,775
Likes: 15
From: Perth, WA, OZ
look for weepy hoses,, but more likely a dodgy cap
be sure the cap with spring ( pressure relieving cap ) is on the point where the overflow spout goes to the bottle
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From: North Dakota
So if the FC has larger coolant seal walls does that mean they can handle higher or lower psi than a FD? I feel like 13psi is just not enough. I have had my coolant system professionally pressure tested up to 18psi with no leaks.
i have used 1.3 bar and currently use 1.1 bar ( summer ambient is beyond 100 F )
s4.5 hybrid engines
the 1.3 bar led to a fail of the coolant jacket on one engine
( truth be told it wasn't the best plate there already,, and i was using viton coolant O rings , and it lasted a fair while and was taken out on a very hot day )
[ btw the viton ring stayed intact ! ]
in oz,, where propylene glycol is not easy to find ,, and temps can be "excessive" then the 1.1 and 1.3 bar caps are the way to go
( provided the engine cooling system is maintained and healthy )
you guys do know that the FD initially came with the high pressure systems,, and dealers retrofitted the 0.9 bar stuff due to factory bulletins
( obviously concerned about the coolant seal wall issues ,, FD pates can be very thin cooling seal walls compared to s4/5 )
s4.5 hybrid engines
the 1.3 bar led to a fail of the coolant jacket on one engine
( truth be told it wasn't the best plate there already,, and i was using viton coolant O rings , and it lasted a fair while and was taken out on a very hot day )
[ btw the viton ring stayed intact ! ]
in oz,, where propylene glycol is not easy to find ,, and temps can be "excessive" then the 1.1 and 1.3 bar caps are the way to go
( provided the engine cooling system is maintained and healthy )
you guys do know that the FD initially came with the high pressure systems,, and dealers retrofitted the 0.9 bar stuff due to factory bulletins
( obviously concerned about the coolant seal wall issues ,, FD pates can be very thin cooling seal walls compared to s4/5 )
talking head
Joined: Apr 2008
Posts: 2,775
Likes: 15
From: Perth, WA, OZ
i wet tested the aftermarket chord coolant seals to 40 psi ( s4/5 plates )
FC plates tend to have a little more meat around the coolant seal groove than the FD
both FC and FD plates feature the groove in the iron,, was previous ( and later rx8 ) engines have the groove in the alum housing
i use the 1.1 bar cap because i need the extra margin in the cooling system
i would would be perfectly comfortable with the 1.3 again if the situation arose
( bear in mind i cut my own coolant seals and rate them as a better / more enduring seal than stock seal when combined with less than new parts )
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From: North Dakota
<iframe width="560" height="315" src="http://www.youtube.com/embed/fAz3TZQNzWo" frameborder="0" allowfullscreen></iframe>
I ordered a 1.3bar cusco radiator cap today. I cant think of anything else that will help me with this and im pretty sure it will work.
I ordered a 1.3bar cusco radiator cap today. I cant think of anything else that will help me with this and im pretty sure it will work.
Last edited by Shorkyz; Oct 8, 2011 at 01:49 PM.
Joined: Mar 2001
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From: https://www2.mazda.com/en/100th/
i have also seen cars with dirt/small imperfections on the cap or sealing surface act the same way. the worst offenders are the FD's with aftermarket AST's those things fail more than the factory ones!
Try the oem mazda thermostat, some new hoses, and the oem .9 bar rad caps from mazda as well.
I know they're overpriced, but I had a similar issue at the start of this season, where there was very low pressure in the system, and I did all those at once, to narrow out the 'easy' stuff, and it solved my problem.
I know they're overpriced, but I had a similar issue at the start of this season, where there was very low pressure in the system, and I did all those at once, to narrow out the 'easy' stuff, and it solved my problem.
Joined: Apr 2005
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From: And the horse he rode in on...
When you say 'boils it out' what exactly do you mean?
Does it puke the coolant suddenly say, when you drive on the highway and then shut it down? That would sound like a pressure cap problem.
Or does it gradually over several trips leave excessive coolant in the overflow tank until finally the radiator is low on coolant? This is a common issue with FC's. It has been discussed in many many threads. Often this is caused by a leak in the coolant overflow hose, or as in my case a very small crack in the thermostat housing, a bad overflow hose combined with a bad seal in the waterpump. The leaks may not leak coolant(much) but may allow air to enter the cooling system when the system should be sucking the expanded coolant back out of the overflow tank.
After I posted this, I found another leak in the waterpump seal.
Good luck!
Does it puke the coolant suddenly say, when you drive on the highway and then shut it down? That would sound like a pressure cap problem.
Or does it gradually over several trips leave excessive coolant in the overflow tank until finally the radiator is low on coolant? This is a common issue with FC's. It has been discussed in many many threads. Often this is caused by a leak in the coolant overflow hose, or as in my case a very small crack in the thermostat housing, a bad overflow hose combined with a bad seal in the waterpump. The leaks may not leak coolant(much) but may allow air to enter the cooling system when the system should be sucking the expanded coolant back out of the overflow tank.
Get the pressure test. If it passes, get a new MAZDA radiator cap.
Before you start to rebuild the engine, try everything else first.
Does the coolant expand into the tank as the engine warms up? Then does it correctly pull back into the radiator when the engine cools? You can have a vacuum leak between the cap and the overflow tube that allows air to be sucked into the radiator when the engine cools. Then some of the coolant stays in the overflow. Next time you run the car the process repeats.. Eventually you are low on coolant. At this point when you run the car, the hot air and steam is bubbling into the tank and the car acts exactly like it has a blown coolant seal, only it doesn't. At this moment, you will be in very great danger of overheating your engine.
I had this exact problem with my 90 Vert N/A. I tested everything, compression, cooling system pressure test. I replaced my rad cap, my tstat with oem. The problem still existed. When the overflow tank got full or when the low coolant buzzer went off, I poured the overflow tank back into the radiator. I found I wasn't losing coolant, just moving it one-way into the overflow tank. I didn't know to test the overflow tube for a leak, so I lived with it like this for months. I then eventually changed the cooling system over to Evans NPG+ and went the nonpressurized route. It works great for me, but I don't recommend it for anyone unless they have thoroughly sorted out the cooling system and are very sure that EVERTYTHING is in perfect operating order.
Good luck.
Before you start to rebuild the engine, try everything else first.
Does the coolant expand into the tank as the engine warms up? Then does it correctly pull back into the radiator when the engine cools? You can have a vacuum leak between the cap and the overflow tube that allows air to be sucked into the radiator when the engine cools. Then some of the coolant stays in the overflow. Next time you run the car the process repeats.. Eventually you are low on coolant. At this point when you run the car, the hot air and steam is bubbling into the tank and the car acts exactly like it has a blown coolant seal, only it doesn't. At this moment, you will be in very great danger of overheating your engine.
I had this exact problem with my 90 Vert N/A. I tested everything, compression, cooling system pressure test. I replaced my rad cap, my tstat with oem. The problem still existed. When the overflow tank got full or when the low coolant buzzer went off, I poured the overflow tank back into the radiator. I found I wasn't losing coolant, just moving it one-way into the overflow tank. I didn't know to test the overflow tube for a leak, so I lived with it like this for months. I then eventually changed the cooling system over to Evans NPG+ and went the nonpressurized route. It works great for me, but I don't recommend it for anyone unless they have thoroughly sorted out the cooling system and are very sure that EVERTYTHING is in perfect operating order.
Good luck.
Good luck!
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Joined: Aug 2011
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From: North Dakota
I guess from what i have experienced it "pukes" the coolant out. I just got home from my dads place and it was fine, shut off the car and heard no bubbling/spewing in the catch tank then for a split second after shut down i heard a few bubbles then it stopped again. So it is has to be the cap because i have already put a new waterpump in and the thermo housing is not cracked. Like i said in a post above it has been tested up to 18psi with no leaks so it has to be the weakest link!
When you say 'boils it out' what exactly do you mean?
Does it puke the coolant suddenly say, when you drive on the highway and then shut it down? That would sound like a pressure cap problem.
Or does it gradually over several trips leave excessive coolant in the overflow tank until finally the radiator is low on coolant? This is a common issue with FC's. It has been discussed in many many threads. Often this is caused by a leak in the coolant overflow hose, or as in my case a very small crack in the thermostat housing, a bad overflow hose combined with a bad seal in the waterpump. The leaks may not leak coolant(much) but may allow air to enter the cooling system when the system should be sucking the expanded coolant back out of the overflow tank.
After I posted this, I found another leak in the waterpump seal.
Good luck!
Does it puke the coolant suddenly say, when you drive on the highway and then shut it down? That would sound like a pressure cap problem.
Or does it gradually over several trips leave excessive coolant in the overflow tank until finally the radiator is low on coolant? This is a common issue with FC's. It has been discussed in many many threads. Often this is caused by a leak in the coolant overflow hose, or as in my case a very small crack in the thermostat housing, a bad overflow hose combined with a bad seal in the waterpump. The leaks may not leak coolant(much) but may allow air to enter the cooling system when the system should be sucking the expanded coolant back out of the overflow tank.
After I posted this, I found another leak in the waterpump seal.
Good luck!
Joined: Mar 2001
Posts: 31,837
Likes: 3,234
From: https://www2.mazda.com/en/100th/
I guess from what i have experienced it "pukes" the coolant out. I just got home from my dads place and it was fine, shut off the car and heard no bubbling/spewing in the catch tank then for a split second after shut down i heard a few bubbles then it stopped again. So it is has to be the cap because i have already put a new waterpump in and the thermo housing is not cracked. Like i said in a post above it has been tested up to 18psi with no leaks so it has to be the weakest link!
Joined: Oct 2003
Posts: 1,600
Likes: 49
From: Norcal/Bay Area, CA
It's leaking from the overflow bottle cap because it can't handle the pressure, so you decide to increase the pressure? I don't see how the rad cap is going to help. Get a new overflow bottle cap. Pressure testing won't tell you if there is an issue with any of the overflow tubing or cap, so don't rule them out.
Finally watched the video and that's an odd one.
Finally watched the video and that's an odd one.
Joined: Apr 2005
Posts: 3,785
Likes: 30
From: And the horse he rode in on...
Those two tiny unshrouded fans? What are those, 10" maybe 12" fans?
I couldn't tell if they were running in the video, but look at the size. They are not covering 30% of the radiator. There is no way they are providing sufficient airflow for the application, especially considering that the majority of the radiator face is not experiencing *any* airflow except for ram air when the car is moving.
Either shroud the belt driven fan or fab a shroud for the 'twins' so they can cool the entire face of the radiator.
Look, the problem may ultimately not be the fans, but having 3 (yes 3) unshrouded fans on an FC is not a good idea. When trouble shooting eliminate the obvious.
Shrouds and an OEM cap is where I would start.
I would also do a cold cranking coolant seal test. Just in case.
I couldn't tell if they were running in the video, but look at the size. They are not covering 30% of the radiator. There is no way they are providing sufficient airflow for the application, especially considering that the majority of the radiator face is not experiencing *any* airflow except for ram air when the car is moving.
Either shroud the belt driven fan or fab a shroud for the 'twins' so they can cool the entire face of the radiator.
Look, the problem may ultimately not be the fans, but having 3 (yes 3) unshrouded fans on an FC is not a good idea. When trouble shooting eliminate the obvious.
Shrouds and an OEM cap is where I would start.
I would also do a cold cranking coolant seal test. Just in case.
Thread Starter
Junior Member
Joined: Aug 2011
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From: North Dakota
I do have the shroud for the stock mechanical fan which i put a new fan clutch in but im still sceptical if the new fan clutch even works.
I've ran 3 different set ups:
Stock fan w/ Shroud - I've been told this is the absolute best setup because it pulls the most CFM
Stock fan w/ Shroud and 1 electric fan - worked best for keeping coolant in the system
Stock fan and 2 electric fans - lowest coolant temps
I've ran 3 different set ups:
Stock fan w/ Shroud - I've been told this is the absolute best setup because it pulls the most CFM
Stock fan w/ Shroud and 1 electric fan - worked best for keeping coolant in the system
Stock fan and 2 electric fans - lowest coolant temps
Those two tiny unshrouded fans? What are those, 10" maybe 12" fans?
I couldn't tell if they were running in the video, but look at the size. They are not covering 30% of the radiator. There is no way they are providing sufficient airflow for the application, especially considering that the majority of the radiator face is not experiencing *any* airflow except for ram air when the car is moving.
Either shroud the belt driven fan or fab a shroud for the 'twins' so they can cool the entire face of the radiator.
Look, the problem may ultimately not be the fans, but having 3 (yes 3) unshrouded fans on an FC is not a good idea. When trouble shooting eliminate the obvious.
Shrouds and an OEM cap is where I would start.
I would also do a cold cranking coolant seal test. Just in case.
I couldn't tell if they were running in the video, but look at the size. They are not covering 30% of the radiator. There is no way they are providing sufficient airflow for the application, especially considering that the majority of the radiator face is not experiencing *any* airflow except for ram air when the car is moving.
Either shroud the belt driven fan or fab a shroud for the 'twins' so they can cool the entire face of the radiator.
Look, the problem may ultimately not be the fans, but having 3 (yes 3) unshrouded fans on an FC is not a good idea. When trouble shooting eliminate the obvious.
Shrouds and an OEM cap is where I would start.
I would also do a cold cranking coolant seal test. Just in case.
Joined: Mar 2001
Posts: 31,837
Likes: 3,234
From: https://www2.mazda.com/en/100th/
Thread Starter
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Joined: Aug 2011
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From: North Dakota
Joined: Apr 2005
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From: And the horse he rode in on...
Except that you ejaculate coolant all the time! Something doesn't add up.
Extra pressure from the cap is not going to help anymore than having three fans will help.
What are you doing for the main thermostat? I bet it is either faulty or you don't have one.
Extra pressure from the cap is not going to help anymore than having three fans will help.
What are you doing for the main thermostat? I bet it is either faulty or you don't have one.
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