Steam from cooler cap.

[Shaun70]

Hi. I was just out in my tr6 and after about an hours drive turned into a supermarket car park. I heard a ‘pop’ sound and steam started to rise from under the bonnet. When I inspected the radiator the pipe going from the radiator cap to the overflow bottle had blown off (it is old and brittle), I assume that was the ‘pop’ and the steam was coming out of the small nipple that the pipe is supposed to be connected to. The temperature was reading normal on the gauge. Any ideas what may have caused the pipe to pop off and why there was so much steam? 
 

cheers.

[john.r.davies]

Does a TR6 have an 'overflow' bottle?     To catch coolant displaced from the block by the small amount of gas there expanding in the heat, so that it may return when the car cools?    Older cars may have just dumped it on the road.
 

As to why, I think you have answered it!  "Old and brittle" like us all!

John

[Shaun70]

Hi. Thanks. It does have an overflow bottle, yes. I have ordered a new pipe but I assume that the steam means something is wrong? Or is the steam normal if you remove this pipe?

[john.r.davies]

Hot coolant is escaping - a normal effect!    - of course it steams, especially in this weather!

[Shaun70]

Ah. Thanks. So its not necessarily a sign that the engine was over heating? I just saw the steam and thought something was terribly wrong. 

[Colin Symonds]

It's escaping from a sealed pressurised environment, which raises the boiling point, to the atmosphere with normal 100C boiling point, thus the steam.

Edited December 30, 2023 by Colin Symonds

[Shaun70]

Thanks. I don’t understand how its sealed though as the overflow bottle is simply a bottle with a hole in the lid through which the overflow pipe goes?

[BlueTR3A-5EKT]

5 minutes ago, Shaun70 said:

Thanks. I don’t understand how its sealed though as the overflow bottle is simply a bottle with a hole in the lid through which the overflow pipe goes?

Shaun, does this help with your understanding of how the system works?

 

https://mechanicbase.com/coolant/how-a-radiator-coolant-overflow-tank-works/

 

 

[Shaun70]

Very helpful, thanks. I guess the pipe that goes into the overflow bottle has to be under the water level? Could the fact that this overflow pipe blew off the nipple on the radiator cap have caused any problems like air being taken into the cooling system?

[Shaun70]

I have done a bit of searching and I am a bit worried the head gasket may have ‘blown’.  When I turned the engine off just now there was a very clear gurgling sound coming from the radiator area/overflow bottle.

[FatJon]

1 hour ago, BlueTR3A-5EKT said:

Shaun, does this help with your understanding of how the system works?

 

https://mechanicbase.com/coolant/how-a-radiator-coolant-overflow-tank-works/

 

 

This does miss a very important point. When the cooling system cools the vacuum draws the coolant back from the expansion bottle and into the radiator. That little valve in the radiator cap is an inspired bit of tech.

[Shaun70]

One more thing. How full should the actual radiator be?

[RogerH]

Hi Shaun,

 just above the vertical pipes you see inside the rad.

 

Roger

[Shaun70]

Cheers.

[charlie74]

On 12/30/2023 at 1:48 PM, Shaun70 said:

I have done a bit of searching and I am a bit worried the head gasket may have ‘blown’.  When I turned the engine off just now there was a very clear gurgling sound coming from the radiator area/overflow bottle.

If you had a blown head gasket and were getting coolant into the combustion chambers, you would see your exhaust turn white…

[Shaun70]

Thanks. I am getting a new overflow hose and cooler cap. Hopefully this will fix it.

[Steve-B]

On 12/30/2023 at 6:48 PM, Shaun70 said:

I have done a bit of searching and I am a bit worried the head gasket may have ‘blown’.  When I turned the engine off just now there was a very clear gurgling sound coming from the radiator area/overflow bottle.

Shaun, 2 little tests I learned with a K-series engine to check if you’ve had head gasket failure to try. Caterham’s sometimes ate head gaskets which was why those of us with higher Bhp cars updated our gaskets. The below isn’t a perfect set of tests however they’re so easy to do.

1. Take 1 panel of kitchen roll and roll it up diagonally into a small straw. Open cooled radiator cap and dip into the fluid. If it’s coolant colour you’re likely ok however if it’s brown, black or smelly (oil or petrol) you may have an issue. 
2. Check the dipstick on a cool engine and closely look for only oil and not brown/ brownish mayonnaise because if mayonnaise you may have an issue. Should this be mayo-like drain a small bit of oil from sump, if same you likely have an issue. 
 

Fingers crossed for your not having either!

Edited January 1 by Steve-B

[Ian Vincent]

You can buy a little kit for checking off the head gasket is blown on eBay. They consist of a cork and a small glass or plastic S bend into which you put a small amount of a chemical. This then plugs into the radiator filler while you warm up the engine. The expanding gasses in the radiator pass through the chemical in the S tube and a change in colour warns you of a potentially blown gasket. 

Rgds Ian

[Ralph Whitaker]

The type as used on the TR5 and 6 could more correctly be described as a catch bottle where the radiator has a pressure cap fitted as per a normal radiator, and any water that is pushed out past the cap seal, such as expansion when the rad has been overfilled, is directed into a catch bottle. Upon cooling down and the water in the engine contracting and causing a vacuum, the suction opens a small valve in the radiator cap and allows water back into the radiator from the catch bottle, the pipe from the radiator to the catch bottle is open at the catch bottle end and therefore should never be "under pressure", being there purely to transfer excess water to the bottle and back again.

If the pipe blew off with a "pop", and the stub then emitted lots of steam, that to me would indicate a sudden increase in pressure overpowering the rad cap and pushing water out quicker than the breather hole in the catch tank could cope with.

In all engines the water in the block gets hotter when the engine is switched off because the pump stops circulating the water  and the block and head are still hot, but in a big cast iron lump such as the TR6 this can be enough to push the water past boiling point and may have been the reason why it chose that moment to force a load of water/steam out, and the old and rotten rubber pipe could not cope, although Shaun states that the temp gauge was reading normal at the time.

Ralph

[Lebro]

Agree with all of that, & that's the system I have on my TR3, & it works.

Bob

[RogerH]

The Temp gauge could read normal but have localised heating elsewhere remote from the Temp sensor.

 

Also remember to have the bottom of the catch tank pipe cut at an angle of 45' or so.

To stop it getting sucked onto the bottom of the catch tank.

And to always have enough coolant in the tank to allow 'Refill' suction to take place.

 

Roger

[DRD]

19 hours ago, Shaun70 said:

Thanks. I am getting a new overflow hose and cooler cap. Hopefully this will fix it.

Good idea to get a new radiator cap as the original may not be holding the correct pressure - hence the sudden release of coolant.

[TR Rob]

3 hours ago, Lebro said:

Agree with all of that, & that's the system I have on my TR3, & it works.

Bob

My TR3A just vents straight onto the road! I know this as on my first trip out I forgot to manually turn on electric fan when parking and as I got out I was met with a trail of coolant on the floor. On returning to the car after it had cooled down I checked the coolant level and it was about 20mm deep in the built in radiator ‘header tank’

I think it had overflowed as it had been possibly over filled prior to me picking up car.

Seems very stable at this level.

Did think of adding something like a TR4A expansion tank, but not sure where to fit it….if indeed it is necessary ?

Any thoughts from anyone ?

[Ian Vincent]

My TR3a also vents straight onto the road if I overfill the radiator but once it’s done it the level stays pretty much in the same place without any need for topping up. So I’ve never bothered with an overflow tank. 

Rgds Ian

[TR Rob]

Thanks Ian, think I will leave well alone and just make sure I keep coolant at present level.