Boiling coolant?

[Natec91]

Hi!

So I had my first ever rx7 delivered up to me this week and it’s got a few little niggles ( I don’t think they’re too serious )

first and most worrying is that I can hear the coolant bubbling/boiling once the cars been switched off … the temp gauge sits steady in the middle of hot and cold so it’s not overheating
Is this just a case of renewing the coolant or is this a known issue?

there’s a couple of other issues but I’ll not ramble on!
Cheers!

 

[Satoshi-FD3]

Where do you hear it from? Have you isolated the location?

 

[Natec91]

Front centre mainly mate

 

[Satoshi-FD3]

If you start it a few minutes into the sound, do you get any white smoke from the exhaust? Do you know the history of the build? TBH that sounds more like coolant in the twin turbo pack.

 

[Natec91]

If you start it a few minutes into the sound, do you get any white smoke from the exhaust? Do you know the history of the build? TBH that sounds more like coolant in the twin turbo pack.

I’ve asked the dealer I bought it off if they’ve anymore history but I think it’s a case of sold and now we don’t give a …
The only receipts I’ve got with the car are:

engine rebuild at 109k km in 2014 at RX Motors? (it’s now at 115k km ) so it’s probably been sat a while

turbos replaced back in 2014 also
There’s a touch of smoke on start up when cold and that goes away but I thought that was normal

what do you mean start it a few minutes into the sound? Fire it up while it’s warm? If so I’ll give that a go tomorrow as she’s all tucked up

 

[Ceylon]

Is the hose from the AST to the expansion tank warm? Could be a faulty pressure cap, I'd check that first.

 

[Natec91]

Is the hose from the AST to the expansion tank warm? Could be a faulty pressure cap, I'd check that first.

I’ll give that a check .. how do you tell if it’s faulty? Just a dodgy seal
Thanks for the help!

 

[Ceylon]

I'd replace it, they are a common failure point.

The OEM gauge is not linear. It will stay on "Normal" until it's really hot then suddenly rise fast. You can do a mod to linearise the gauge or most people opt for an aftermarket gauge to read the temp.

If when you replace the cap you're still getting the boiling noise while the motor is running then report back. When the car is turned off it is quite normal to hear bubbling and gurgling noise from the turbos for a few minutes.

 

[Natec91]

Great thanks mate

Ordered a new cap and some
Fl22 coolant ill get it all swapped out and report back Noise is coming more from the front of the car opposed to where the turbos are sitting so hopefully it’s just the cap

 

[MILLION]

I get that. It's the air separation tank doing its thing

 

[CarbonRX]

Ive recently found that if you have the correct amount of coolant in the overflow tank it stops this from happening. Having recently changed the complete cooling system mine was boiling over when I turned off the car. once the coolant levels are correct in the car, you top up the expansion tank and it all works correctly without any issues of boiling or bubbling. The AST vacuum's water back in from that tank so it appears to be quite important you have it all set correctly hence the overflow tank having a full level on the dipstick lid.

 

[Natec91]

Okay I’ll try all of this when I get in from work, I’ll swap the coolant and cap regardless then I know it’s been done

Is the boiling causing any harm if it’s just in the system
Also I noticed it’s orange and I’m sure I read some where that’s a no go and it should be green?

 

[MILLION]

the coolant wants a flush. I've done it three times to mine now. Very easy and straight forward.

One bung in the engine under the spark plugs. Another bung in the lower left had corner of the rad.

When refilling take the small coolant hose off the top of the throttle body for easy bleeding

This wot be popular. But, the first time i flushed it, i actually used a hose to get it all out as there was loads of shit in it. Then flushed with distilled water (about 10L). Then FL22.

 

[Huds1]

Looks like tap water instead of coolant, and mine used to make a similar noise , it was boiling up tho just the coolant being pushed into overflow and / or retracting back

 

[erachter]

You might want to add a proper water temp sensor.
Fortunately for you I have one for sale with sensor and loom

Greddy 60mm Water Temp Gauge with loom and sensor Supra Skyline RX7 R32 R33 R34 | eBay

Greddy 60mm Water Temp Gauge with loom and sensor Supra Skyline RX7 R32 R33 R34.

www.ebay.co.uk

 

[Natec91]

So I got the coolant swapped out over the weekend, gave it a few flush cycles while it was on the stands until it was as clear as it was getting
Put the new fl22 in, finally gave it a run out last night and the result was no boiling coolant Hopefully that’s an end to that!