Coolant boiling over and spilling from overflow pipe
 

Hi there folks, I've searched other coolant leak threads but just wondering if you guys have a direct answer for my prob.

Basically my coolant is boiling over in the coolant bottle and coming out the over flow pipe.

I don't think my fans are turning on

Could the fans be the direct cause for this to happen?

Or is it possible a blockage in the system could make coolant bubble over ?

Going to check fans today.

Also there's no visible leaks apart from the coolant bottle overflow pipe

Any guidance is a big help!

Cheers

Yes, it could be either of the things you mentioned.
Overheating is very, very serious in the rotary so don't let it get to far while checking it out.
First,with car off I would spin the fans by hand and see if there is any blockage to them. If they spin freely, then it's time to see if they work when they are supposed to kick on.
Then of course you could have a bad water pump, thermostat, and/or blockage.
Do yourself a favor right now and extend the overflow hose down below the power steering connectors and if they have gotten coolant on them from the overflow hose now, then clean them up really well so you don't face the PS issue of it going out later on.

Worth buying a new coolant tank cap. It's a long shot but sometimes the spring can get weak, allowing preasure to be released early, allowing the water to boil. Theyre cheap so worth doing.

More likely you got a fan problem though, if its hot enough to boil, they DEFFINATELY should be running.

Forgot about the cap as a potential issue, but thinking that you'd see some escape there as well and not just the overflow tube? Worth a check for him though for sure.

Hate to alarm you, but unless your water pump has failed, the alternative is your engine is most likely failing. I'm assuming when this is happening, that you are just driving normally, or idling, no serious load on the engine. Under those conditions, temps should be well below boiling and there is no normal cause for the behavior. Fans only come on when the temps are a bit too warm and need a cool down, your problem may just be pressure in the system from seal/gasket failures. Extended idling could do that, but light load driving shouldn't engage the fans. I would suggest you get to a dealer ASAP, if you can do it under its own power, in order to save a tow charge.

My engine failure started like that, me finding green coolant spilled around the overflow tank for no reason, increasing amounts, then finally... new engine time.

^..................depends on how long he's letting it idle........................doesn't it?
If fans aren't operating it will get hot enough to boil(over I'm almost certain).
I seen cases where something has fallen into the fan shroud area and not allowed fans to turn, and boiled over, so he needs to check that and then the fans.
You're right though.....................you don't want to muck around much when debugging and seriously overheat this car.

^^^^^Agreed.

I know the cap is unlikely but I always mention it as i've seen alot of cars (not rotary engines) that had an overheating issue and it turned out to be a £2 rad cap! If the spring is weak, the coolant isn't kept under pressure and therefore the water boils. No, you wont see water comming from the cap, just the overflow tube as the spring allows the rubber seal under it to lift just enough to alow the pressure to be released (as its designed to do), but as its weak, it's letting it happen at 90-100 deg instead of what it should be.

Either way, if youre not good with mechanics, you NEED to get this to a garage ASAP. There is no way we can diagnose something this vague on a forum, anything said is pure speculation.

i can confirm the above. though in my case, it was not the cap, it was some tiny hairline crack in the overflow around the filler neck. i have a water temp guage, so i knew it wasn't a major problem, but it was pretty much impossible to track down until the piece broke off altogether.

Guys thanks for the comments,

Me and my mate tested both fans with a battery and their goosed

Ordered a fan set off eBay and should be here soon

Agree about connector clean good point

"Engine failure" comment scares the crap out of me

I hope the fans sort it.

Thank for your input!

Don't forget to extend the coolant overflow hose down below those connectors.

Filled coolant and later that evening while idle the front of my car was steaming
 

So did i add too much coolant and thats just the excess coming out or is there a bigger problem? Fans still turn on, no overheating on my gauge, A/C was cold then hot then cold

Did you open the hood to see what was steaming and where? Maybe you were roasting a rabbit or something. We can't even begin to provide an answer to why you had steam until you can give us WHAT was steaming :)

It only did it that one tiime and byt the time i looked at it it wasnt steaming anymore, the coolant lid cap broke off very easy and i ordered a new reservior and hoping that was the only problem

More than likely was.................some bottle lips have cracked and/or given way. That would produce steam. It may have just cracked and you finished the job.

Coolant is coming out of the over flow tube of the coolant tank. Thermostat is good, also changed the coolant cap. Please help! 2004 rx8

I had this problem and it ended up being a crack under the cap seat as pictured.

It wasn't obvious for being so out in the open, but I found it by pressurizing the tank to like 5 psi by holding my hand over the cap seat and lightly shooting an air nozzle in between my fingers hoping to listen for leaks. When I first heard the leak under my hand I thought it must not be sealed well but then I knelt down and saw the crack.

Did you put too much coolant in? There's a max fill line on the passenger side of the bottle, if you go too far over that it will come out of the overflow as the car warms up.

When does it come out? Is the car overheating?

once the engine gets to normal temp the water in the coolant tank starts to boil and comes out of the over flow tube. all the water drains out. also slow compression at taking off

Coolant boiling over after new rad cap
 

I just recently replaced my OEM rad cap with some aftermarket cap from jiffy lube. I had my fluids all checked and a oil change done and the pressure on my OEM cap "failed" they replaced my cap with a new one and filled my coolant tank up. But now when I drive the car it boils over and squirts out the backside of the cap. I've had 2 new caps put on since I had this done (two days ago). I let the car cool off and it looks like all the coolant had dropped out of the caR. Could over filling cause boiling?

Did u check for the small hairline crack under the rad cap as mentioned above here in the Thread?

If the cooling System can't buildup pressure the coolant will boil earlier.....

Greetings
Thomas

I'm having similar symptoms.

Car details:
- Replaced expansion tank (brand new Mazda)
- Replaced rad cap
- Flushed cooling system thoroughly
- Fresh coolant, proper ratio and type
- Radiator appears to be in great shape
- Undertray is in place
- Cooling system was bled following Mazda recommendations

If I drive the car hard (such as autocross, or track, or highway pulls), I will get a small quantity (just dribbles) of vapor and coolant spurting / spitting from the overflow tube. The temperature needle never moves from optimal, so it is not due to over-temperature (needle starts moving at about 230F thanks to thread below). The radiator fans kick on when needed (typ. sitting stationary). The upper and lower radiator hoses are both hot, suggesting flow through the thermostat (unless this assumption is wrong???)

Maybe I'm a pessimist, but if I'm getting over-pressure without overheating, SOMETHING other than temperature is overpressurizing the cooling system. I suspect something blown inside the engine allowing combustion pressure to over-pressurize the cooling system. I've heard this could happen on rotaries.

To troubleshoot, I plan to borrow a cooling system pressure tester from Advance Auto. If I'm truly getting overpressure, and not overheating, i'll look into causes of excessive pressure (obstructions, or internal engine failure, others???) I could also have the overflow bottle "sniffed" for CO gas, which would indicate combustion gases leaking into the cooling system.


Any other recommendations for why I'm getting overpressure without overheating?


...

You can be well over 220 f before the needle begins to move. I made a thread showing the temperature it actually moves at. I can't remember the thread name. But a weak radiator cap can cause it if your above 212f. Or bad engine seals. My first test for bad seals would be remove the cap and let the car idle up to temp. Maybe monitor the obd water temp to get an accurate temp when it starts boiling. If it's over 212 then I'd start by replacing the radiator cap.

Thank you for the link. I've replaced the radiator cap twice.


"My first test for bad seals would be remove the cap and let the car idle up to temp. Maybe monitor the obd water temp to get an accurate temp when it starts boiling. If it's over 212 then I'd start by replacing the radiator cap."


I'm not following; if the cap is removed, how will this diagnose a bad cap?

It would test for bad seals. If they are bad then it'll probably boil over below 212f.

Are you overfilling it? It's an expansion tank. The coolant level goes up by approximately 1 inch when hot. Don't fill it up all the way. Keep it at the F (Full) level when the engine is COLD. If the coolant level is at the F mark when the engine is cold, it should be about an inch higher than the F mark when the engine is hot.

Regarding the blown coolant seal theory, do you get white smoke from the exhaust when starting it in the morning? That's a dead giveaway. If you don't, the easiest way to test for an internal coolant leak is, like you said, to do a coolant system pressure test. See if the pressure drops.

With that said, RX-8s have a weak cooling system. A lot of these cars overheat on the track.

Good luck and keep us posted! :)

I rented the Advance Autoparts cooling system pressure tester. My system seemed to hold pressure when I pumped it to ~10psi, and my cap seemed to hold pressure when I pumped it to ~13 psi.


Would coolant start to vent past the radiator cap, even when the needle hasn't moved past 12-oclock? I'm going to either get a an aftermarket water temperature gauge or a scangauge to measure my temps while on track.

Coolant is at "L" when cold, and just above "F" when hot, so it's not overfilled.


I do not get smoke from the exhaust.

12 o'clock is 237f. So yes it could.

Did you do the test with the engine hot and cold?

Coolant boiling over and spilling from overflow pipe
 

This is something that everyone who tracks their car should do.
You want to monitor a few areas.

If it's at "L" then your coolant level is low. Fill it up to the "F" line. Half an inch above the "F" is perfect.

poo;4735053]12 o'clock is 237f. So yes it could.

Did you do the test with the engine hot and cold?[/QUOTE]

Yes.

No bubbles when cold.

Some bubbles when fans are cycling on/off (engine hot with cap off).

Adding a thorough amount of radiator ducting foam has eliminated the boil-over due to improved cooling. however, I suspect I'm still running hot so I will improve the sagging undertray and run a higher percentage of water and see if that helps.

Get a Bluetooth OBD2 adapter off eBay and monitor your temps. That will tell you for sure if you're running hot or not.

Running a higher percentage of water will cause it to boil sooner. Ask me how I know.

Or dump that coolant altogether and go waterless: Evans waterless coolant, prevent engine overheating

How can it boil sooner? Coolant is only used to stop the liquid from freezing. Not boiling. The system is pressurized to stop it from boiling.

The ratio of antifreeze to water in the coolant effects the boiling point of the coolant.

Derp.

I run Evans, it works very well. The only downside to it is getting it, so you always have to have extra on hand or reuse what you drain out if you are working on something.

i plan on adding oil and water temp gauges to confirm the actual temps (and oil pressure, of course).

Extremely good foam sealing, using a zip tie to prevent undertray sag, and a 70% water solution seems to have solved my cooling issues. Thanks all!

Glad it worked and many thanks for updating us. What are the temps? :)

my data logger works through a laptop so I can't use that on the track. real gauge set is next. but I am seeing 200F after several hard 2nd/3rd gear pulls without cooldown.

Something else worth considering is backflushing the radiator fins. I find that this car's radiator and condenser collect a lot of junk that needs to be washed out every once in a while.

Im having a similar problem too and i found a blockage in one of my fans. I don't know how long its been there. Both of my fans don't turn on at all. If one fan is blocked will the other fan still turn on? I replaced the fuse already. Are the motors to the fans individual? Should i replace my entire assembly?

Yes they have individual motors. Yes if one fan is blocked, the other will still turn on. I'm guessing one of the rubber grommets from the air filter box tray dropped through the hole and jammed the fan. They're right above the fan blades. You don't need to replace the whole fan assembly but you might have to replace the fan motors. First check if they're getting power. Check the fan relays. If they work, directly give power to the fans and see if they spin. If they don't, time for a new motor.

At one point I had a fan issue where it appeared and acted like a stuck fan, but turned out to be a brush inside the motor that became unseated and stopped the fan from turning properly or passing current.

The fan setup is kind of interesting so if the passenger side fan is damaged neither fan will come on until the high speed mode is engaged (which, in the case of a bad passenger side fan still only turns on the driver's side fan).

Nah I had these dirt wasp things build a nest and it stopped the driver side fan from spinning. But the passenger side won't turn on either even though it appeared to be free spinning and moved when I spun it by hand. That's why I was asking if one is stuck will it stop the other. How do I test to see if power is getting to the fan motors?

Jump the fan relays. You test the fans by directly wiring them to the battery. Don't worry about the polarity. It's not a problem.