ASH8

To me if that much 'cold' water is disappearing it is like you have large air pockets in system.

I know this sounds a little contradictory but your Cooling System needs to be 'as normal as possible' as in no air pockets, it needs to be bled first, then has to be engine hot and TS open...to do bubble test..seal leak test.

Return water with compression bubbles comes back via Top Radiator hose and CB return hoses.

And you are not having cold or hot start issues?

The coolant seal test is no different than checking for banger Head Gasket Coolant Leak, it's just not so violent (usually) with Rotaries, unless the Coolant Seal has a hole in it about half an inch!...then it won't start anyway (usually).

RIWWP

iTrader: (2)

Note, the coolant doesn't just disappear and never come back. If I let off the gas and it returns to idle, the coolant level returns to where it was at idle before I increased the revs.

Where it goes? I don't have the answer for that. It would imply that there is alot of air somewhere in the system that is getting displaced by the coolant getting pushed through the block, but when it returns to idle the air goes back to wherever it was, pushing the coolant level back up.

I would also guess that if there IS a chunk of air somewhere, this air heating up is over-pressurizing the coolant system causing the overflow.

But then the question gets back to "where is it coming from?" since I've bled the system several times, including popping the throttle body lines with the car on an incline, with the heater on max. Unless I'm just not ever getting it bled completely?

RIWWP

iTrader: (2)

Agreed about the importance of bleeding, see my last post. I'm following the instructions, I don't know if I'm actually getting it completely bled.

No, I have no starting issues at all. Fires right up in under 1 second of cranking, hot or cold, even if it's sat without starting for a week (as usually happens now, haven't driven it more than ~20 miles in the past 3 weeks while trying to solve this) And no smoke on startup either. So suggesting that I don't have puddles of coolant/water sitting in the housing accumulating until I try to start.

ASH8

If you are running your car with cap off then YES any car will overflow coolant at idle when hot as system is trying to pressurise...without correct pressure cap it will overflow on any car.

RIWWP

iTrader: (2)

Understood.

ASH8

As I have said before....the seal bubble test has to be done quickly, No mucking around.

It is cap off, revs up and look inside...all in 10-15 seconds...with ALL the Hot Coolant Cautions removing Cap.

1.Apart from that, I would have said wrong Cap...but your Miata was OK
2.Air In system.
3.Coolant Seal.

Perhaps someone else can chime in?

ASH8

I would still go for a Genuine Cap N3H1-15-205....for the $15 it is worth it.

Anyone here with an old Coolant Bottle (sensor replaced) with a 'good cap', or someone that could lend Pearl an RX-8 'Cap'.?

Mr_Pieper

Could the cap be good but the bottom isn't sealing properly? This could lead to either the spring being useless or not taking as much pressure to allow coolant past.

RIWWP

iTrader: (2)

I hear you loud and clear Ash. Never fear, I respect the pressure and heat of a hot coolant system. Never know who else might be lurking that doesn't though

I sent a PM to CRH asking him to take a look at this thread when he has time, since his experience with both engines and cooling systems should be able to assist with a diagnosis as well. I'll probably be "mucking about" with the problem all weekend, and using as much of the public water supply as I need to do it. Might even temporarily replace some of the CB hoses with clear ones just to see if I can see air movement through those. Or make a BIG loop of clear hose to the throttle body to see if I can get air to get trapped up there


If I can find any conclusive evidence that it's the bottle or cap, I'm going to be ordering a brand new set from Mazmart. I really don't think it's the cap, but I can't rule out that the bottle itself isn't allowing the cap to seal. Which is why I'm not inclined to just keep throwing money at caps. If I replace the bottle, Mazmart's listing adds the OEM cap in as well so I'd be back to OEM at that point.

The cap/bottle point doesn't explain how this air is getting in the system though, so I am not confident that the problem is there.

ASH8

OK, just logged on to tell you...this has been bugging me...so I doubled checked my new parts..

NC Miata/MX-5 Radiator/CB Cap is 16PSI.

All RX-8's N3H1-15-205 is 13 PSI...NOT 16 PSI .....as I said this cap is ONLY used on the RX-8 CB.

I would not trust a non genuine (Advance Auto) Rad Cap...have you had it tested @ 13 PSI, is the spring identical to OE, seal, etc?

nycgps

iTrader: (1)

I think i have a new cap somewhere in my garage, if u need it i can sell it yo u, thats if i can find it tho

Or i can just lend u my cap to test

Oh have u check the bottle's tab to see if its holding the cap properly?

RIWWP

iTrader: (2)

Ash, the Miata cap I tested is for the 1999 NB, not the NC, and it is 13psi, just like the RX-8.

However, no, the caps are not the same. The generic one has a spring external to the center "shaft", the Miata cap apparently has it's spring internal. The handles for gripping are different dimensions, however they have the same size and type sealing right, retaining cap, and gripping flanges. I have them sitting side by side in front of me as I type this.

If I had any suspicion at all that it was the cap, I'd have already ordered an OE one from Mazmart. The local dealer here is a tiny shared dealer, and they don't really stock Mazda parts that I can find.

With the same expected rating between the two cars I have and each cap fits each car just as snuggly, I would expect that a cap failure problem would have just transferred the problem to the Miata when I swapped caps. However the Miata did perfectly fine for 150 miles of driving, including slogging through I-80 traffic into the office yesterday morning. And the 8 continues to push coolant and air out of the overflow.


IF it's a failure at the cap/bottle end, then I would suspect the bottle itself is not allowing the cap to seal. But that doesn't explain the reaction of the coolant level when I increase revs, it doesn't explain how after reving I have more air in the system that gets pushed out at idle that wasn't before.

This is why I'm going to substitute two of the normal lines with clear lines today to test with, to see if there is actually air getting pushed around the system, and when. (No, I'm not going to keep it that way, I know this tubing isn't designed for the heat of the engine bay, and if it fails while I'm standing there it's easy to instantly shut off the engine, not going to drive with it like that)


I'll take video of behavior and post it. Have a few errands to run with the wife over the next couple hours, so I'll start posting updates and results this afternoon.

RIWWP

iTrader: (2)

Ok, thanks Ray. It's a better / more detailed diagnosis of what I was headed toward anyway.

Since I still have 1,400 miles left on the 12k service warranty from my replacement at 96k, I have a chance at getting a replacement covered. Any recommendation in how I approach the dealer for a replacement? I don't think a compression test would fail at this point, or within the next 1,400 miles?

RIWWP

iTrader: (2)

Sounds good.

Fortunately the infamous (famous?) Wayne Mazda is 45 minutes away, just got to find out if the service warranty is good between dealers or just the issuing dealer.

If I get turned down or not viable, I'll be chatting engine rebuilds with you

RIWWP

iTrader: (2)

Yeah, I expect that to be the case. Just want to have Mazda Corp validate it



I'd just grab a personal loan to cover it in the short term and start pulling this engine. I've said the remans are good for 10,000 to 100,000 miles, just didn't expect to be on the short end of that stick



Shrug. Not terribly concerned about it.

9krpmrx8

iTrader: (46)

Did you ever send off the oil to be tested? I am pretty sure it is a coolant seal same as my last motor but the oil test confirmed it for me

RIWWP

iTrader: (2)

Yes, last week.

Posted this elsewhere earlier:

9krpmrx8

iTrader: (46)

So did you get the results back from blackstone?

RIWWP

iTrader: (2)

Haven't been contacted by them yet. Not sure how long the usual turn-around is.

9krpmrx8

iTrader: (46)

It's quick, shouldn't take long at all before you get a call or email.

RIWWP

iTrader: (2)

Well, sent Thursday, so "not long" would be last Friday? Today? Tomorrow?

9krpmrx8

iTrader: (46)

I would expect you to hear from them today or tomorrow. Depending how the mail. You sent it USPS?

RIWWP

iTrader: (2)

Ash, Ray,

I think this tells the story. This is after the engine is up to temp, thermostat open, and after about 3 minutes of my wife holding the RPM at 2,500. The video is at idle, then back up to 2,500rpm.

The tube is a section of clear tubing I added between the upper coolant bottle return hose and the bottle specifically for this test.

Aerated water.

ASH8

It is when your wife raised the revs is when you check for a bubble string, (hard to see then, vid finishes).

The rotaries I have viewed (Coolant Seal failure, Coolant entry) for a minor blow back it is a constant fine bead around the size of a 'pin' head.

A small match head size bubble string and larger you would have major starting issues...Coolant use/ entry.

Repeat...you have to keep revs high 2500-3000 and constant.

RIWWP

iTrader: (2)

Yup Ash. We did that before I grabbed the video. It basically looks like aerated water, pinprick bubbles. You can see them gushing through the tube in the video as a gush or whiter water. All bubbles. You can also see farther to the right along the tube where they were collecting on the inside of the tube and releasing as they accumulated enough. When the revs first come up in the video you can see the entire tube water flow turning white, and it's all air bubbles. (or some other gaseous substance)

Is basically a solid stream, though the volume changes at different times, idle OR higher revs.


It's definitely there, no doubt about it.