Water Boiling noise!Did it happen to you??
 

I dont know if this is happening to some of you or not, but some times when im driving around with my totally stock 93 FD and stop and turn off my car.....

after a few seconds i start hearing water boiling under the hood, but its a light boiling not really strong, which is not making the Water going out at all.....

is this normal or does it indicate something???

That's the coolant locally boiling at the hot spots in the engine once the coolant is not moving after shut-down. In the stock FD, this is normal, especially with the 13-psi AST cap which was put on in one of the recalls. However, many people use a variety of methods (FC thermoswitch, fan mods, etc.) to lower coolant temperatures to prevent this.

Thanks Man for the answer...

What year of the FC is that thermostat??

What temps are u seeing in Saudi?

I don't think Mazda tested the cars there in the heat.

Did u have the radiator upgraded?

check ur radiator cap too

The item is the THERMOSWITCH that turns on the fans. IIRC, the FC (2nd gen RX7) does it at ~205F vs ~221F for the FD version.

I don't think it is 'normal', I think this indicates that you are getting air into your system.

I was getting these noises until I replaced the caps.

Before I did the Miata thermoswitch, I had mild "boiling" noises whenever I parked the car after driving more than 15 minutes in hot weather. There was no air in my cooling system. Since I did the Miata (same as FC, but different electrical connector) thermoswitch, it no longer does it.

i have the boiling sounds too
hopefully mine is normal...

Are you also seeing any white smoke coming out of your exhaust at start-up? I had that water rushing sound after shut off when my car's coolant seals went bad due to over heating- necessitating a rebuild. I hope that this isn't the case for you.

oh man...thats exactly whats happening with me
bit of white smoke at start up and a bit of water rushing sounds after turn off
:(

Game over.

Which is better? How do you perform this mod?

Don't get alarmed unless you are losing coolant. "A bit of white smoke" at startup could just be your engine burning off condensation that accumulated overnight, and the "water rushing sounds" could be caused by the aforementioned localized boiling.

My FD lets off a little white smoke on cold mornings after start up. I figure it's mostly water vapor or something because my coolant never goes down and the car runs fine.

I only had the boiling sound once... I was racing the car at a track and I went off track and got stuck. I didn't know if I had damaged my car or not so I shut it off. I could definately hear mild boiling. Normally I'd wait several minutes before shutting off after driving the car hard.

I've heard that sound before myself but in my situation, it was because the reservoir was low which left some air pockets in the engine. After topping the system up with coolant and bleeding the air out of the system, it went away. No more boiling noises.

i just did this on sat, i took the car out for a drive about 20 min of light drivng around 60 mph and oh yea i added disstilled water to it before i left becuase im on 122,789 OEM miles, so i get back home and i was taking something out of the trunk and then there it happend i heard this strong rush of gurggling sound, and then i open the trunk and it was my coolant over flow tank spillin over like it had to much to drink on a friday night, so i let it be and it went away, i wonder if i put to much water in the system. let me know if you guys have done thins

lets hope thats the case
my cars been running fine and theres no coolant loss
and the white smoke only happens after i garage the car for over 3 days straight.
but thanks for the info.
leaves me at peace for a bit...

you are gangster my friend!

HOLD ON GUYS! That sound is perfectly normal for a stock setup. Upon hard operation or prolonged slow operation at high temperatures, some water bubbles over into the AST after the engine is shut down. Sounds like a coffee pot percolating. I've been driving my FD going on two years now. No deteriortation in power, performance or anything else. Your suggestion on the FC thermoswitch is something I haven't tried yet. If it reduces water temps that much, I say go for it.

i have a koyo rad and aftermarket ast and mine boils on a hot day

i like cabbage

The FC thermoswitch is better because its connector is the same as the FD's, so it's easier to install than the Miata one that doesn't match the FD connector. Otherwise, their function is the same.

happens to me after a spirit drive

OK. The FC thermoswitch it is..... Now.... Should I go to the Parts department at Mazda and ask for it by name?..... How much is it and where is this installed?

I had the same thing happen to me with my FD when I first got it. It was totally stock. Once I got a downpipe and did the fan switch modification, I have not had the coolant boil after shutting off the engine.

LOL. You know what that reminded me of? At the local stealership (it's a Mazda/Nissan one), the parts dept. has a huge poster of a Maxima (95 - 99 body style) that's split in half. One half shows the Maxima in a desert w/ super high heat...the other shows it in a super cold area w/ iceicles hanging from it. The poster says something to the effect of their cars are tested in the most extreme of conditions lol. But still, like I told Jed, I'd be worried about the dry sustained solid heat of Saudi. You can crack your dash in a single day if you leave it in a hot area w/ continued sun exposure. I know ppl who have had it happen. They can see temps up to 140 degrees!

Most stealerships won't have them in stock, and if they don't they'll tell you you have to buy 12 of them at a time because that's the minimum they can order LOL. Such bull. Just call Ray Crowe @ Malloy Mazda: 1-888-533-3400. Ever since Dale Clark discovered the switch fits right in, Ray started stocking the switches.

Now...about this boiling sound. I know most of you guys said this is normal for a stock car, so the chances of you having a water temp gauge hooked up is prob slim...but...anyone know what kind of temps you're getting when hearing this boiling sound? I'm guessing there's a correlation between how hot the engine gets and getting the boiling...

The problem is that the coolant temps always rise after shutdown due to heat soak from the hot engine with zero circulation of (and no cooling airflow for) the coolant, so the actual temp at that point is kind of irrelevant.

Good point. I love your explanations lol. :)

So what's all this talk about AST caps? I'm gonna take a stab at this, and hope I don't miss the mark too bad lol. As Dave said, the Pettit AST caps are rated at 13 psi, while the original stock ones (on 93s AFAIK) were rated at almost 19 psi. The lower pressure caps decreases the pressure in the coolant system, depressing the boiling point, thus increasing the probability that your coolant will boil over? I don't understand why you'd wanna do that...

And IF my conclusion's right, the other part that's leaving me :scratch: is that most of us run a 50/50 mix (or close to) of coolant + water, right? And since coolant doubles as an anti-freeze, it lowers the freezing point and raises the boiling point of the coolant mixture. So it seems to me that running the 13 psi caps is counter-productive...you're losing the positive effects of running a water + coolant mixture, that would have otherwise allowed for a higher boiling point. I don't think you'd want your coolant to boil at a lower temp (or boil at all, for that matter)...so my guess would be that we're using lower pressure caps simply because there are negatives/dangers in running a high-pressured coolant system that I don't know of? And, those dangers are worse than the possibility of boiling your coolant?

A highly pressurized system puts more stress on the hoses and connections. You're more likely to see catastrophic failures such as hoses splitting or popping off. In addition, ethylene glycol is slippery and flammable. You don't want hoses bursting and spilling coolant on your tires or hot engine components.

-s-

I've done that before. I put to much water in and it came out of the overflow tank. It spilled once and it was fine.

OK...now im assuming that i should change my radiatior Cap and the thermoswitch to have my car cool better...will try my best.

the sound isnt actually a boiling sound..its like a running/slushing sound
only happens for about 30 seconds

and no matter what kinda driving conditions, i always pop the hood when im done with the car to cool it off to be on the safe side

I was under the impression that even after shutdown water circulates as long as the thermostat is open.Are you sure aabout the zero circulation?

Once the water pump stops, circulation stops. Super heated water inside the engine will not move to any great degree. Only the heat will radiate, usually upwards until the blanket is saturated, then it should convect sideways into other metal engine parts. Lastly, non metal parts, hoses, etc will heat soak. Low mass parts, closest to exterior air movement will be the first to cool off and will eventually draw heat away from engine and turbos. There's not much air movement inside the engine bay, unfortunately, so convection is the only way that heat is going anywhere once the fans stop. Opening the hood after hot operation would seem to be a very good idea. At least that's what my physics classes would seem to suggest.

I do that any time I can.

I second that.

I get mucho white smoke on startup, for the first 2 or 3 mins, but it dissapears at the edges, doesn't smell like coolant, and I haven't had to top up the coolant in months. The smoke has been getting worse in the cold weather (winter down under atm). It's just moisture.

I used to get some localized boiling, but now I use my turbo timer to run the fans after shutdown (about all it's good for!) and drive gentle for a bit before I park, and I don't have localized boiling anymore.

I use Evans NPG+ at zero pressure and NEVER get boiling sounds :D

Thanks :)

Jed, as Dave mentioned, this was part of the recalls. Like I told you earlier, since you have a 93, make sure you call Mazda and check if all the recalls have been performed. Any recalls that have indeed been performed will result in a sticker on the door jamb on the driver side. That's a positive sign (if you find any of these recall stickers), but it doesn't mean that all of them have been performed.

So to sum up this thread boiling noise bad, better cooling effeciency and opening your hood to better air flow good.

I'd say that boiling noise is NOT necessarily bad, but, of course, things to help the engine stay cooler ARE better.

Yup... So do I .... I always pop the hood so my rubber hoses don't get crispy and so I can help extend the life of the motor....

i was at the dealers picking up some clips for my shifter panel today
and saw some guy with a riced out 3rd gen.
i asked him why he had this jaguar emblem on his hood
he said it looked "sleeper"
man he was smokin some good shit

just a random flashback

:eek: :ar:

You didn't leave the FD suffering like that, did you??? :nono:

mmm...bruchies..

I used to get some mild boiling noises when I had a worn coolant filler cap. After I replaced it, I have yet to hear/see any boiling.

The boiling will not acutally -hurt- anything, though it may break down the coolant a little quicker. Usually, boiling after shutdown is caused by low coolant - in the engine. Check the coolant level in the overflow bottle - it may be very full. Follow my dissertation:

Think of the engine as a coolant pump to and from the overflow bottle. When the engine warms up the coolant expands and forces its' way through the overflow tube into the overflow bottle. When the engine cools down it creates a vacuum, which sucks coolant back from the overflow bottle.

This works fine until one of your coolant caps develops a vacuum leak at the rubber seal. Then all that happens is some percentage of the coolant in the engine is pumped into the overflow bottle and remains there, leaving the engine a little low. This allows the pressure to drop after shutdown (because air is compressible), which in turn allows the coolant to boil after shutdown. The metal in the engine holds a lot of heat when the engine is running, and this is ok as long as there is coolant flow to carry it away. Once the flow stops, the coolant will heat up more than normal, and if the pressure is low enough, it will boil.

The classic event run is you notice the engine coolant level is way down (checking when cold, of course) when you look in the water pump fill tube. You pour in more water. It gets pumped into the overflow bottle (to stay as you have a vacuum leak and can't get it back to the engine). You are now nervous, and check the level in the engine every day (morning when the car is cold), and fill it. Soon (two to three days) the overflow bottle is full to the top and leaks out where the filler tube (removeable) joins the bottle. You see the puddle and panic.

It happened to me. Solution - replace both caps (they were old), replace all small coolant hoses to/from overflow bottle - they are not designed for pressure use as there is no pressure in this part of the system, so they are thin and can be collapsed under suction - stopping the coolant from returning to the engine. I replaced them with suitable pressure coolant hose routed so it would not kink (it's thicker so care must be taken when routing it - it will not bend as well).

I have not had coolant boiling after shutdown since - 6 years running now.

Hope this solves your problem.

new motor here it come.

Lots of white smoke on start up for the first 2-3 mins, lots of boiling bubling noise after shut down.

No problem on cold start, idle high as normal but car stalls once idle goes down to normal within first 5-10 min of start up. Once car warms up properly no stalling problem, weird.....