just drain the Radiator first before u do it.

then just fill it up again with new coolant mix.

 

If your OEM radiator is 5-7 years old plan on replacing the radiator!! The plastic crystalizes and you will snap off the little tit when you try to remove the reservoir. Either have a replacement radiator on hand or plan on letting your car sit for a few days while you wait for an new one.

Replace the radiator and then ask the Dealer about replacing the reservoir for free under extended warrantee?

 

I'm in the process of replacing the overflow reservoir right now. Got the old one out which was a little tedious. Those hoses need a little persuasion to come off.
I used an oil extractor pump to get the coolant out of the bottle so I only got a very little spill when removed the reservoir. All fluid I removed was just the volume in the reservoir, didn't drain the rest.
When the new bottle is installed and I'm filling up the system with coolant, do I need to be careful with air in the system? Any way to avoid that, or should I not worry because the air will escape anyway?

My car is 7 1/2 years old but I had no issue with this.

 

^...................you have enough posts to know that search is your friend!

Anyway, some people just raise the front end and have the car idling while they continue to top off until full.

The other way........is................

After performing repairs or any time cooling system coolant is drained, the cooling system must be purged of air. Use the following procedure below to remove air from cooling system:

1. Safely elevate front of vehicle. Elevating the front end only, at a steep angle will allow air trapped in system to escape easily.
2. Temporarily remove a coolant hose to the throttle body.
3. Fill coolant system with proper mix ratio of coolant / water per work shop manual.
4. Start engine and carefully monitor coolant level, topping off as necessary.
5. When coolant begins to flow from throttle body hose, air is bled from system.
6. Carefully attach coolant hose back to throttle body pipe. **Caution, coolant may be extremly hot!
7. Verify proper coolant level and add as necessary.
8. Check system for leaks.

Probably makes the most sense if you drained from both the radiator and engine drains, but can't hurt if you just do the 8 steps.

 

Thanks.

Regarding taking "a" coolant hose off the throttle body... can I take off the top one that's easily accessible without having to remove anything? Or from the bottom (which is harder to reach without removing other things)?
It was not completely clear to me when searching

I wonder if removing the hose is really necessary or the easiest method ("raise the front end and have the car idling while continue to top off until full") will suffice. Is this more risky than the other?

 

Answering in reverse order.............but............
IMO it wouldn't really matter as to which method is better than the other.
Your other questions is.................yeah, you would want to take off the higher one as what you really want is the highest point in the system. Given this statement one could assume this method might be slightly better.\

In any event, take special care if removing the hose that leads from the raditaor to the coolant bottleh as if you break the plastic piece there where that hose connects, then it will be "new" radiator time.

 

I'm done with the replacement. Decided not to remove the coolant hose from the TB, just raised the front of the car and let it idle for about 10 minutes while monitoring the coolant level. Didn't have to top off the coolant, so looks like there wasn't any air in the system. Makes sense since just replacing and refilling the reservoir probably didn't get any air trapped in the hoses.

Drove 40 miles after that and everything seems to be normal.

 

Not sure what I'm missing in trying to replace my reservoir. I removed the two nuts, removed the battery (but not the battery tray). There is just not enough float or room left to pull the resivour back to clear the front body cross member. The battery tray looks like it's held in place with one bolt in the middle and one on the drivers side rear, outside.. but that is very difficult to get to. I don't see any 'easy' way to remove the reservoir? Any tips?

I'm having the occasional coolant level light and figured I'd either try to fix the sensor or replace it.

 

The battery box has to come out.

 

Yep, that's what I figured. Is there a trick to getting that rear battery box bolt out? I couldn't work a socket or open end wrench on it.

 

the bottom hose is a PITA, that aside it isn't too difficult

http://www.finishlineperformance.com...cat=336&page=1

 

I have never had trouble getting the battery box bolts out. Just move the hose out of the way and use a open end or ratchet.

 

Sounds reasonable but on mine there's a plastic bracket directly above the bolt preventing me from getting a socket on it and I can't seem to get even a short open end wrench in from the rear. I'll have to try again.

 

You won't be able to 'fix it' as the float itself loses the ability to - well - FLOAT!

It is in a sealed side section of the bottle so you're stuffed!

 

I just had dealer replaced mine a week ago. So the person told me mazda has came out with a new and improved overfill tank that should fix the problem. Hopfully thats true so my coolant light wont miss fire again.

 

I'm curious, if that is true, why the dash light goes out when the speed drops.

It is a magnetically operated "reed" switch. This is very similar to window/door proximity alarm switches in buildings.
With a full bottle, the float is 'up' and the contacts are 'open'.
When the float drops, the switch contacts should 'close'.
I need to take a closer look at the switch to see if it actuates the switch in the 'full' or 'low' state and if the switch is normally open or closed.
The comment that the float is losing the ability to float, just doesn't seem to work for me. I looked at mine and it seems to be floating just fine and my dash light comes on during every drive.

My thought is the magnet has lost some of it's magnetism and it's not strong enough to keep the contacts apart. There is a momentary closure of the contacts that ECU detects. The ECU then turns on the dash indicator and it remains on until the speed drops (not sure why that is).

 

because when you slow down, there will be more coolant in the tank.

the float absorbs too much coolant in the first place so it was never "float" as high as it supposed to be. That's why when you have that "I wanna go fast" mood, the light comes on.

 

One problem may be that some people don't know not to use anything but distilled water with their coolant mix. If you use well or tap water the solids/minerals/etc will come out of solution and build up on the interior surfaces. This could impact the float level device as well.

 

Or..............you could just read!!!!!!

https://www.rx8club.com/series-i-trouble-shooting-95/coolant-bottle-greatest-secrets-revealed-182793/

 

Let me ask a question...on some car when you loosen the radiator drain plug and the drain starts and when you tighten the plug the drain stops. So you can drain a certain amount not a full flush. Is it the same on the rx8? i.e. Can I drain from the radiator only until the coolant are out of the reservoir and stop?

 

When I changed my tank to a modified 240sx tank all I did was drain the old tank and I didnt have any problem with it leaking anywere just catch what ever is sitting on the tank and you should be fine

 

Short answer is.............."yes".

 

lol good. thanks! I was gonna use a pump to pump coolant out of the bottle, thinking the drain plug is just the same as the engine drain plug, that it's messy to control the flow. Then I found out that it's not that on most car, so I don't need to be worried.

My landlord got a dog, and I don't want to spill coolant everywhere so the dog can stay away from my car.

 

I used the pump method when replacing the overflow tank, and it worked fine. Made the process very easy.

 

Just did this today. Getting that bottom hose that connects to the radiator off, and then on to the replacement reservoir was a PITA.

All in all, though, simple and easy enough. No more annoying light!