Brown stuff in coolant
 

Bubbles usually mean coolant seal failure. Do you have any other symptoms, such as white smoke on startup?

Brown stuff can be caused by Redline Water Wetter.

Never use tap water in the cooling system, unless you are planning to thoroughly flush the entire system with distilled afterward. Distilled water costs 80 cents per gallon. There is really no excuse for using tap water at that price

Does the smoke smell sweet?

It could be Water Wetter scum, if you have used Water Wetter. WW is well-known to cause brown and black scum in cooling systems, where modern coolants are used. It is an outdated formulation that should not be used, except with pure distilled water. Even then, there are better products, such as Motul Mocool.

The bubbles and history of overheating are not great signs, but you can easily confirm if there is a seal breach with a block test (tests coolant for exhaust gas).


Whatever the cause, drain the junk you have in there and thoroughly flush the system, and refill with FL22. Random coolant is bad for the seals and tap water erodes metal.

Never knew that about tap water..... oops.

Yeah, depending on where you live, tap water can be hard and leave mineral scales in your cooling system, which reduces its efficiency as well.

I don't see why you would not use FL-22. At least in North America, it's not very expensive and available at any Mazda dealer.

Good news on the block test.


Zerex Asian Blue is fine to use in your RX-8. The second paragraph in this document is why. If you use it, be sure you flush out all the old coolant with distilled water, unless you really like the color brown.

I have not used Zerex Asian Blue, but I have used Zerex Asian Red in my Tacoma, and after 5 years and 100K miles, it looks just like the genuine Toyota coolant did after the first 5 years and 100K miles, which is pink and perfect.

Also, Amazon sells Mazda FL22, although the price has increased recently. People report buying Ravenol concentrate and mixing with distilled water with good success. It should be fine as well.

Crazy white smoke!!!
 

Hi everyone I’m sorry to bring this up in this thread, but I’m confused by something that happened to my car recently and thought this thread could help.

I have a s1 05 Rx8 148,000 miles 6speed

I noticed a misfire in rotor 2 code and a flashing cel so I changed my plugs. So far that fixed the cel light and the misfires. Once finished I tried starting the car and it wouldn’t start. Against my better judgement I cranked it again and tapped the gas to about 3500rpms and let go. It was about 40 degrees outside so kinda cold but I cloud of white smoke came out of my exhaust for about 15-20mins followed by a sweet coolant smell. Once the car was nice and warm the smoke cleared and the smell slowly went away. But the cloud literally covered the street. I drove it around monitoring everything and nothing out of the ordinary happened, it had great power and idled very well. The next day I checked the coolant reservoir and it was a little low not much of a surprise though. The reservoir looked a little dirty so I filled it up. I then started the car and no smoke at all. It started great and drove amazingly when redlined. Not sure what happened?

I thought I blew a coolant seal but it’s driving amazingly and there wasn’t any smoke on a cold or hot start up and it’s driving is great. Has anyone ever experienced anything like this before or might know what happened?

if there is a coolant leak into the engine
when you let the car sit for a day or two, the coolant leaks inside the combustion chamber
and when you start the engine it puffs out the smoke

"condensation" is normal on cold days
but if you can smell coolant and the smoke is thick enough you can't see through it that is a very bad sign
anyway, just drive the car around like normal and check if the coolant is getting lower or let it sit a few days then start it and see if you get another smoke cloud

have you ever had an engine rebuild before? 150,000 miles is a champion

if you do have a coolant seal failure you can check by driving the car around on a hot day and then stopping, open the coolant reservoir and see if it is bubbling.
in serious cases, the coolant will be pushed out and spill all over due to the combustion gases expanding and you can pressure test the coolant system.

Thank you for you fast reply! I actually let it sit a day before changing the plugs and I always suspected there could have been a very small leak but not a bad one. I also premix when I gas up and figured some of that smoke could have been from that, but it’s unlikely that it would make that thick of a smoke.

Would it smoke like that if it was somewhat flooded?

It is is the original engine for the car I picked it up almost a year ago and I’ve been fixing a few things on it. I run 10w30 motor oil. I had a rotary specialist check my compression a few weeks ago and he said the numbers were higher than his race cars 13b. And he also helped me out and hooked me up with a new coil system that runs with 98 Chevy truck coils I believe and that’s made a huge difference in performance so far.

Other than that one giant smoke smoke cloud I didn’t see it do anything strange when I drove it yesterday. Also the sweet exhaust smell went away. I was gonna drive it today and see if there are anymore strange symptoms.

Do NOT do this.

Borrow a block tester from the auto parts store and test your coolant for combustion gases. This is the safest, most accurate method for testing the disposition of your seals.

Thank you. I think I’ll do that. So far I’ve noticed about 2-3 seconds of thin white smoke on cold startup and some boiling in the coolant reservoir. However the cars driving great. Engine has never overheated before and I’m watching it to make sure it never does. How long do 8s run once they’ve blown a coolant seal, and are there any other symptoms that point directly to it being a coolant seal failure?

Thin white smoke is just condensation. Perfectly normal.

And yeah, DO NOT attempt to open a hot coolant reservoir. I once opened a lukewarm one in a Civic and it still sprayed a good bit. I am already pretty dumb for doing that. Now imagine a bigger spray with boiling water and steam.

If your coolant is boiling on idle, perhaps your fans aren't turning on. See if they work.

Between 0 and 1000 hours. To confirm either get a block test, as suggested, or check your spark plugs for deposits, but even that isn't super conclusive, so just get a block test.