Boiling Over

[nigelt]

So I have re-plumbed the overflow/expansion bottle to come off the radiator and blocked the other pipe as per Steve's suggestion. However I used a length of clear pipe so I could see what was happening. First the radiator started sucking back the coolant from the bottle in fits and starts until it was empty. Then after a little longer, it flowed back into the bottle and out the little breather hole, about a foot into the air. Now this is no great pressure, because if I squeezed the pipe off, it didn't try and push the pipe off the radiator, which is not a tight fit. I looked at the cap and it looks like a 0.8Kg/cm which works out to be just over 11psi. If it is supposed to lift at this pressure then I would have expected the coolant to have gone higher than a foot.

 

So I'm thinking this cap is faulty but also is 11psi a bit low anyway?

 

Nige

[Guest Gargoil]

I may be teaching people to suck eggs but make sure the overflow/expansion bottle isnt sealed. Mine has a cap on it that when screwed down seals the bottle from the air. This means that when the engine cools and it tries to suck back the water, it cant.

[Guest Gargoil]

While I am on a roll of egg sucking, is there too much coolant in the system? You just need a little in the bottom of the expansion bottle so there is plenty of room for the water in the system, to expand to. You may even want a bigger bottle. I only mention these two things because I have had something similar happen to me recently. When I stopped screwing the cap down on my bottle everything worked as it should and it found its own level after a few heat and cooling cycles.

[Guest chris brown]

Also have you got the right rad cap? It needs to be one with a rubber seal in the top of it to ensure water is sucked back into the rad when it cools. I must admit by what you have said it does sound like a head gasket failure.

[nigelt]

Thanks for all the replies,

 

Definitely the right cap, as it has the two valves inside. The outer one for overflow and the inner one for the vacuum. So yes it draws the coolant back in. I will try tonight to blow and suck on the pipe, ( a clean bit ) to see if the cap is sealing correctly. I may also have an air lock now, as I noticed that the pipes around the auto choke were not getting hot. Failing all that yes we maybe looking at a head gasket.

 

Nige

[Guest mower man]

Would sooner have a 14 psi /1.1 kg cap than the one you have fitted my ops only mower man

[nigelt]

Hi Mower man,

 

Yes it was the one that came with the kit and I thought it was rather low.

 

Nige

[Guest chris brown]

I agree with Mick 14lb is what it should be which would raise your boiling point to about 120 degrees C

[Al Milton]

Just to add to the advice given, check that the rubber seal on the rad cap is fully sealing to the radiator.

This was one of the contributing problems to the boiling over issues I had.

 

On my rad, with a new cap fitted, there wasn't the 'witness mark' fully around the seal. So I cleaned up some gunk from the mating face of the rad (it was new rad anyway but still had some 'gunk'), fitted a slightly thicker rubber seal to the rad cap just to be certain and this eliminated the problem of the weeping rad cap.

 

There is a test you can conduct on the head gasket, if the obvious emulsion is not present. It was recommended to me by Longboarder and some others. Go onto the Frost Auto website and get a bottle of indicator fluid (can't remember if this is the correct name). You sample your coolant and add to the fluid. If there is a colour change, then exhaust gases are present in the coolant and this could be overpressuring the cooling system. A lot simpler and cheaper than taking the head off if you don't need to.

 

Process of elimination unfortunately

[nigelt]

That's a great idea Al, I will look into that.

 

I disconnected the auto choke today, as it sits slightly higher than the top of the rad. Ran the engine and after a while I had some overflow, but not too much. I left it and all seemed to settle down, found its own level as Gargoil suggested. However, I am now concerned that the level is a bit on the low side. I will also look to get a higher pressure cap. Any suggestions where? the ones on CBS don't seem to have the middle valve to allow the drawing back of the coolant from the expansion tank.

 

Cheers

 

Nige

[Bob Tucker]

You need the one that has 2 rubber seals.....I think its this one.....check with CBS first tho'

http://www.carbuildersolutions.com/uk/radiator-cap-chrome-rubber-upper-seal

[Guest mower man]

That's a great idea Al, I will look into that.

 

I disconnected the auto choke today, as it sits slightly higher than the top of the rad. Ran the engine and after a while I had some overflow, but not too much. I left it and all seemed to settle down, found its own level as Gargoil suggested. However, I am now concerned that the level is a bit on the low side. I will also look to get a higher pressure cap. Any suggestions where? the ones on CBS don't seem to have the middle valve to allow the drawing back of the coolant from the expansion tank.

 

Cheers

 

Nige

Got mine from Halfords [it was Sunday],,take care there are 2 lengths l and s , believe it inc in part no, a long cap may just be bludgened into short rad neck and locks every thing up ,a short cap falls into a long neck and not seal properly !!!!!! mowerman :search:

[nigelt]

Just to keep you posted,

 

Al mentioned a chemical test that could be done to prove if the head gasket has had it. Its called Block Tester and it starts off blue and if there is any combustion gases in the coolant system, it turns yellow.

 

Mine turned yellow, so I have a gasket failure, well lets hope that's all it is.

 

Off to the garage to start the strip down.

 

Cheers for all the advice everyone.

 

Nige

[Al Milton]

Hope you get it all sorted.

The sun is on it's way out at last!

[nigelt]

Just a BIG thank you to all.

 

Head gasket changed and now sweet as a nut.

 

Cheers

 

Nige