coolant issues, or rebuild required? :S

[hcDave]

I have a 1986 RX7 (non turbo) and it's acting strangely... It used to be that when I was on the highway it would overflow the coolant and give me the low coolant warning and I would have to stop, let it cool down, and refill it. This only happened once in a while and never while driving around town. Then it started to occur more frequently on the highway (every 50km of constant travel) and finally, now it's occurring around town :(

I had the radiator rodded and have replaced the rad cap.

I have done some research, and think it is either a bubble in the coolant system (there is supposed to be a kit which resolves this - if anyone knows of a link to this, please let me know) or a seal has failed (is there a way to test for this without pulling the engine apart?)

I have run the engine with the rad cap off and added coolant until there are no more bubbles present - this seems to help, but does not resolve the issue. I can also idle the vehicle up to operating temperature and it does not overflow (within 15 minutes of starting the vehicle anyway)

Any comments and suggestions are most appreciated!
Thanks in advance.

Dave.

[Phoenix7]

1. do you have an underbelly tray? I ask because without one, the air doesn't go through the radiator at higher speeds.

2. what's having "a radiator rodded?" don't know what you did.

3. By removing the cap and turning the car on you should have gotten rid of all the bubbles in the system already. A sign of coolant sel failure is if you turn your car on every morning and WHITE, SWEET, SMOKE comes out of the exhaust.

4. Have you checked your stock fan? maybe the clutch-fan has failed and isn't pulling air through the radiator? You still have a stock shroud right?

Gotta be frustrating.....slowly tackle these things and don't let it overheat anymore.

[hcDave]

Hi Phoenix,

I do have an underbelly tray - but the cover that helps to divert air into the air intake (right hand side looking at the vehicle, right in front of the intake) is missing - I have put in some cardboard (temporary fix)

Rodding out a radiator is the process of removing the radiator tanks and pushing rods through the radiator core to clean it.

I talked with a mechanic at Mazda the other day and he said that without the kit it's next to impossible to get the air out of the system. He could not find the notice in his book though, and was quite busy, so suggested I try to find info about it online...

I just went out to check if there was any sweet white smoke when I started it and there wasn't any - do I have to wait until morning? (the car had been sitting for a couple of hours) I also noticed that the coolant level in the reservoir had returned to normal (I will edit that in my original post)

The fan seems to be turning fine, and I do still have the stock shroud.

Some good news (I hope) is that it has never overheated to the point of boiling over (it did get to about 3/4 of the way though once while I was going over a mountain pass) but I have always pulled over and toped off the coolant as soon as it indicates that it is low. (I hope this does not mean that it is pressurizing due to something other than air trapped in the system)

Thanks again for your assistance!

Dave.

[Rx-7fetish]

The stock fan will still turn even if the fan clutch has not engaged, it will spin but it is free wheeling on the clutch. Try replacing that, the thermostat, and fresh coolant make sure you mix it 50/50 with water. check for absolutely any possible coolant leaks.

[TitaniumTT]

Pressurize the system leave it overnight. If there are no signs of antifreeze on the ground and the pressure is zero, the coolant had to go somewhere. Start the car and look for the puff of white smoke or the sweet smell of it burning in the exhaust.

From what you're describing, you have an iron that is corroded away and when it get's hot enough, is allowing combustion gases into the coolant system. You could also take a sample of your antifreeze and have it analyzed for hydracarbons.

[N.RotaryTech]

Pressurize the system something like this if you can. Requires the water-pump-housing to be taken off. This is from proz07's 3rd gen build thread.

http://rotarycarclub.com/rotary_forum/attachment.php?attachmentid=4394&stc=1&d=1235181848
http://rotarycarclub.com/rotary_forum/attachment.php?attachmentid=4395&stc=1&d=1235182159

[TitaniumTT]

Neat little gizmo. I need to build something like that and like the Fighters Garage Turbo testing kit.

You might be able to borrow a tool that accomplishes the same thing from autozone or advanced that allows you to remove the radiator cap and pressurize the system without removing anything else. I have one. It's worth it's weight in ............ silver?

[hcDave]

Rx-7fetish,

I can hear the fan engage and when the engine gets up to temp. Also, while topping off the coolant with the engine running and the heater on full I could see the coolant flowing by. And the engine does not overheat before loosing coolant :S

Thanks for the suggestions though.

Dave.

[hcDave]

TitaniumTT,

I think you may have hit the nail on the head - I will head out today and see about obtaining something to add some pressure. Thanks to N.RotaryTech for the images - if I can not beg, borrow, or steal something that replaces the rad cap I`ll be building something similar ;)

I`ll keep you guys updated - good or bad...

Dave.

[hcDave]

TitaniumTT - quick question... what's an iron? (I could not find anything via google which referred to engines or cars)

[Rotary Inspired]

The engine consists of 3 irons or side plates and 2 rotor housings. They are sealed together with a total of 8 O-rings and held together with 18 long dowels. On the FC and FD Mazda moved the grooves for the O-rings into the irons or side plates. Unfortunately this was not as good of a design as the previous grooves in the rotor housings. Over time the cast iron plates can rust on the outer side of the groves from the coolant passages. Once it weakens it often breaks. I have fixed one by having it welded w/ a nickel rod and then resurfaced flat. It was a major PITA and I only did it because it was a RE plate. Good luck and keep us posted

[Rx-7fetish]

What TitaniumTT is describing is the same as i was thinking and is also let your coolant into the combustion chamber, where the coolant is going to burn through the engine, meaning that you need a rebuild. The stuff i was getting you to try was stuff to problem solve to rule out everything but a seal. The engine is not overheating until the coolant gets low for that exact reason you have a possible bad iron, or a blown seal, letting the coolant leak into the combustion chamber and then your engine is overheating due to loss of coolant. The only fix is a rebuild. The reason i suspect for your problem getting worse over time is because the "hole" that the seal is letting coolant leak through into your combustion chamber is getting bigger overtime. This is exactly what happened to my first engine when i got my car.

[hcDave]

... I wish it was the fan or thermostat... hopefully it's just a blown seal!

[NoDOHC]

Hopefully it is a leak in the radiator, a hose or the heater core. If it is a blown coolant seal, you will need to tear the engine apart. (Not that that is very difficult).

[rx4ur7]

How many miles on the motor? Life expectance for the FC NA here was 120/140. Or actually 10 years is more the norm. It is more time related here.
Easiest way to tell if it is a motor, fill up the cooland system, leave the cap off the motor fill. Start it and watch for bubbles. The first sign are very fine bubbles that can form a foam. Next stage is larger bubbles where you can see grey smoke when they burst, third stage, water blows right out as soon as you start it. At the first stage it may have to come up to full operating temperature. Some fluid will come out as the coolant expands.
On filling the puppy, raise the nose of the car as high as you can, try to get the top of the radiator higher than the hose that goes into the back of the upper intake manifold, that and the heater are the main places air gets trapped. Open the heater to full hot.
Fill it up, pump the lower radiator hose. Put the cap on run it till it gets to full warm up. Check it after it cools down.
You can also fill it, use a pressure tester to pressurize it. Release pressure and fill, keep doing that.
Another test for seals is pressurizing the combustion chamber with compressed air. This was the test we used at Mazda. Remove leading plugs and add compressed air. Watch coolant level.
Symptoms for seals are overheating, smoke on start after it sits for a while, early on it may take a couple of days,
Overheating can be caused by of course loss of coolant, thermostat, radiator, partially blocked exhaust.
Loss of coolant should be easy to find. If your tester is good and it drops, and no fluid is found externally, and there is none going into the motor, Check your heater core. See if your carpets are wet.