I just got done changing the thermowax pellet on my 86 NA and it bothered me that the highest point in the cooling system is the housing for the thermowax so while I had it apart I put an air bleed in the top of the sensor housing. I used a short 3/16 brake line nut which I tapped to accept a 1/4 20 bolt with an o-ring seal. Then I screwed the bolt into the fitting without the o-ring and ground the bolt and fitting down to half the original length of the fitting so it wouldn't interfere with the coolant flow through the housing. I drilled and tapped the housing to accept the brake fitting. If you drill from the inside of the housing you don't have to worry about drilling a straight hole like you would if you tried to drill the curved outer surface. I used locktite red to seal the fitting into the housing, and the o-ring seals the bleeder bolt. It worked great, and filled the cooling system completely with no air bubbles.

 

just use the plug on the radiator.

 

The plug on the radiator isn't the highest point in the cooling system. It's not even higher than the fill cap is. Wouldn't you want to bleed air from the highest point in the system? I could understand if you said "just pull the coolant hose loose from the thermowax housing" that would achieve the same result as my bleeder, so maybe it is a dumb idea.

 

Your idea seems pretty practical and well done to me...I'd prefer not to mess with waterhoses once they're installed and your method looks relatively foolproof.

 

the radiator screw is where mazda intended you to bleed it from. your supposed to run the engine whille filling through the filler neck with the bleeder screw open. close screw,top off filler neck, your done. read the FSM.

 

Yeah, but Mazda was the same bunch of idiots who used a thermowax pellet for cold start instead of a nice reliable idle air control solenoid like everyone else in the world, then buried it behind the engine so you can't even see the adjuster without a mirror. Do you realize there are 3 seperate systems that control idle on a 13B? They could have had one solenoid and been done with it.

My coolant filling method doesn't require the engine to be running, fan blowing coolant all over as I'm pouring it in the fill neck. Tell me, if your engine's coolant system is empty and the thermostat is closed, how long will you have to run your engine that way before the thermostat opens and allows the air to escape and fill the motor with coolant? What happens when that cold coolant rushes into your hot, dry engine which is running? You won't find the answers in your FSM so I'll tell you. First, what coolant there is in the block turns to steam and if you are lucky it's enough to open the thermostat and the cold coolant rushes into a semi-cool engine and disaster is averted. If you are not so lucky, the engine gets really hot and any coolant which seeps in is instantly turned to steam which pressurizes the block and pushes the coolant back towards the radiator until the thermostat housing itself gets hot enough to open the stat via heat transfer through the block. You won't know this is happening because there is no coolant around the coolant temp sensor. Finally the stat opens and the superheated air and steam blasts up the fill neck right into your waiting face and jug of antifreeze. At the same time, the coolant from the radiator is trying to fill the engine but there is so much heat trapped that it is being turned into steam furiously and the coolant has to fight its way through the whole engine spitting steam out the fill neck the whole time. Rapid contraction of the engine block due to the shock of the coolant causes cracks and seal failures throughout the engine and its game over for your engine.

I'm not against the FSM, in fact I pay damn near $200 per month for Alldata online which contains FSMs for every vehicle from 1982 to the present. As an ASE Certified Master Technician with 22 years experience in the automotive field and my own repair and tuning shop I know how to read the manual and I also know the science behind how vehicle systems work and when I find that a manufacturer made a stupid design, I re-design it so it works better and more efficiently. This mod allows me to fill the engine completely in about 2 minutes and rest assured before I even turn the key that there are no air pockets in MY engine.

 

why would you pour cold coolent into a running engine?if the coolent is about 70-80* its fine. if your coolent is running so hot when your idling the car for 5 minutes to fill up then you have a problem. i just did this to my car a few weeks ago and it went smoothly. i would not suggest ripping the cap off to fill it with coolent after a spirrited drive unless you want to admit yourself to the ER for burns.

 

Hello, I have a Mazda RX7 FC S4 N/A from 1987.

I would like to use this topic to make some questions:
1- The FSM states that the cooling system in this car should be bled with the engine at idle. However, in all other engines that I've worked in my life, the cooling system is to be bled with the engine at 2500 RPM.
What's your opinion on this? Should I do it with the engine at idle or at 2500 rpm?

2- Usually I can tell that a cooling system is bled by watching the cooling fan kicking in while bleeding the cooling system. But this happens on cars with electrical cooling fans, how will I know that the cooling system in this car is bled if the fan is mechanical?

 

1: Do what the FSM says, rotaries aren't like other cars.
2: You take off the upper coolant cap and keep adding until the coolant level doesn't drop below the base of the plastic neck.
3: It's ok to make a new thread when the last one was 5 years old and a slightly different subject.

 

Well, I used this thread because is one of those that I found while searching on the forum that talked about bleeding the cooling system.

What do you mean by "base of the plastic neck"?

 

The upper filler neck is plastic [bolted onto the thermostat cover neck], you want to fill the coolant all the way up to the bottom of the plastic part [so there's no air left in the metal neck that it's bolted to]

Look at page 3-5 in the S4 FSM's cooling system section. Picture 67U03X-009 shows it [the little raised part that his finger is dripping into]

 

Oh, you mean the piece where the cap fits. I see.

Thank you very much for your tips

Cheers.