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Offline sezian

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coolant boiling in expansion bottle
« on: July 17, 2018, 09:00:01 PM »
I'm currently riding round the middle / South of France temperatures are high 20's and my coolant is starting to boil and gurgle in the expansion bottle with some spilling out - why ?

The temperature gauge is normal. The coolant is filled to mid level but after stopping the coolant seems to completely fill the expansion bottle (with some overflowing) before it slowly cools and settles back to normal level ???

I've had various comments from the people I'm on tour with ranging from, head gasket has gone - I don't think so no signs of water in the oil. Thermostat might be sticking, radiator needs flushing - Coolant was changed at 12,000 miles bike has now done 29,000 miles.

I'm planning a full service when I get home which will include a coolant change, I'm also considering a thermostat change (where is it located - easy change?).

Any other ideas suggestions of why this might be happening ???


Offline Rtwo

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Re: coolant boiling in expansion bottle
« Reply #1 on: July 17, 2018, 09:14:57 PM »
The thermostat sticking is the obvious cause

It's below 1&2 throttle bodies and a bit of a pain to get to

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Offline Turbotom

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Re: coolant boiling in expansion bottle
« Reply #2 on: July 18, 2018, 09:37:24 PM »
Could be the radiator cap. It should keep the coolant under pressure.

Tom
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Offline CSAW

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Re: coolant boiling in expansion bottle
« Reply #3 on: July 18, 2018, 11:18:36 PM »
*Originally Posted by Turbotom [+]
Could be the radiator cap. It should keep the coolant under pressure.

Tom

 :028:  That would be my starting point also.

Offline street tango

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Re: coolant boiling in expansion bottle
« Reply #4 on: July 19, 2018, 07:19:37 AM »
Yup. Rad cap.

Offline sezian

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Re: coolant boiling in expansion bottle
« Reply #5 on: July 19, 2018, 08:35:43 PM »
You will have to excuse my ignorance but how does the radiator cap come into play / keep the system under pressure?

The coolant when very hot seems to send loads into the expansion bottle and pretty much fills it up, sometimes to overflowing, which looks like it's boiling and eventually after cooling settles down to around the bottom level marks.

Please explain what changing the radiator cap will achieve ?

Offline street tango

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Re: coolant boiling in expansion bottle
« Reply #6 on: July 19, 2018, 09:00:29 PM »
There is stuff on YouTube that can explain it beer than me on here. They are cheap. Just do it.

Offline Bladerunner99

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Re: coolant boiling in expansion bottle
« Reply #7 on: July 21, 2018, 01:49:18 AM »
I take it you have made absolutely sure that the system is completely free of airlocks. check the rad cap seal or as stated replace the cap.  The system is under pressure when hot which allows the temperature of the water/coolant to rise above normal boiling point.
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Offline CSAW

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Re: coolant boiling in expansion bottle
« Reply #8 on: July 21, 2018, 02:32:45 PM »
*Originally Posted by sezian [+]
You will have to excuse my ignorance but how does the radiator cap come into play / keep the system under pressure?

The coolant when very hot seems to send loads into the expansion bottle and pretty much fills it up, sometimes to overflowing, which looks like it's boiling and eventually after cooling settles down to around the bottom level marks.

Please explain what changing the radiator cap will achieve ?

Correct, the cap does hold pressure in the cooling system.  Pressure raises the boiling point.  Caps are set to a specific pressure.  Once it goes above that pressure it releases coolant to the overflow reservoir until it gets down to the specific set pressure.

When it cools off the cap also allows the coolant to be sucked back into the engine.

If the cap is bad it doesn't hold as much pressure as it should and allows too much coolant to pass to the overflow.  Also not holding pressure allows the boiling point to come down then boil and let the engine run hot.

Hope that makes sense.

Offline AvgBear

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Re: coolant boiling in expansion bottle
« Reply #9 on: July 21, 2018, 04:12:45 PM »
*Originally Posted by CSAW [+]
Hope that makes sense.
Yes it does -- good explanation.
All except this part: "Also not holding pressure allows the boiling point to come down then boil and let the engine run hot."
The reduced boiling point of the coolant may be a problem -- but, it does not (directly) cause the engine to run hot.
(indirectly, if the engine would run low on coolant...)
The engine's operating temperature is controlled by the coolant thermostat and radiator fan.
If the fan runs constantly, the coolant may become hotter than the temps. set by Triumph (i.e., "run hot").
If the fan cycles off & on it isn't running hot.
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