chucking coolant out onto the road when I switch the engine off

[Rubce]

Hi All

Whilst on our day out to Llandudno today, the Stag decided to act up which to be fair to it is pretty unusual. Whilst the engine was running the temperature was fine with the needle in the middle of the gauge. When I came to switch the engine off it then proceeded to dump a load of coolant out of the expansion bottle down onto the road. It did this twice on the run across to Llandudno. As we approached the summit of the Great Orme, the temperature started to climb and kept climbing. By the time I pulled over into a place to park, the needle was almost all the way across. I popped the bonnet and left the entire thing to cool down whilst we had a picnic and flew Toby's kite. After about an hour I filled the radiator back up (+4 litres) and she started up okay. On our way through Deganwy we got stuck in slow traffic and again the temperature climbed. I pulled over as the gauge again reached the top end. Again I let her cool down and then topped up with 6 litres! We then drove top the beach with no problems. On our way home along the A55 she was fine apart from from when we pulled into a petrol station for some sweets. As soon as I turned the engine off she then dumped water onto the road. We stopped once more on the way home but no coolant appeared and again when we arrived home no coolant appeared.

The engine oil looks fine with no trace of water.
No cloud of steam coming from the exhaust pipe apart from on a cold morning start up.
No water in the Vee.
No water dripping from any of the hoses
Cannot see any external defects with the hoses
Fuel mixture seems okay as the spark plugs are a light brown colour.

Any suggestions as to what is causing the coolant to dump out seconds after I switch the engine off?

Regards

Bruce

[andy p]

i had this happen and it turned out to be the filler cap needed replacing

[Danny]

Sorry to say but it sounds to me like a head gasket has blown. I really hope I am wrong an it's what Andy P reckons.

Danny

[martin]

Have to agree, as the engine stops, the last remnant of coolant stops circulating, boils and expands, blowing past the pressure cap. Martin.

[E-LAD]

the coolant in my expansion bottle was doing the same- i noticed this when parking up in a car park.I was worried that it was HGF /After using a block tester on it & coming out negative, i found there to be cold spot areas on the radiator.I have replaced hoses,filler caps and had the rad pressure tested which ended up being recored and replaced thermostat and flushed out system with hosepipe.....i think thats cured it!

[Rubce]

HI Guys

Thanks for your thoughts. I will purchase a new pressure cap and also get my finger out and fit the header tank. I will keep you informed of the results.

Regards

Bruce

[martin]

Hi, if you have a 20lb cap, it won't boil till about 140c, that's VERY hot, and/or pressurised. A header tank will make no difference to that particular problem. Fingers crossed that it's a knackered cap. Martin.

[Richard Saunders]

I had a leak from the expansion bottle when the brass neck fits onto the plastic, but not enough to dump litres of coolant, just enough to let water weep out and air get in...

[flying farmer]

If the cooling system is still pressurised when cold suspect the head gaskets. If there is no pressure then there could be an internal leak, inlet manifold gaskets are a possibility.

Try the cap first, and as Richard says also check the metal ring where the cap sits is properly sealed to the plastic bottle

Neil

[Rubce]

Hi All

Well I have been using the Stag everyday this week to go to work etc and she has behaved impeccably in traffic with no hint of overheating. This is without changing any parts.

As recommended by Martin and others I purchased a new pressure relief cap with a 20psi (140kpa) rating. Went to fit it this evening and discovered it won't fit as the lugs are too wide. Has anybody else come across this problem? The new one is on the left in the two photos. The old one is a 145kpa rating.

I took the opportunity to replace the fibre washer on the radiator filler plug as it looked a bit pasted it.

Puzzled

Bruce

[martin]

A little difficult to tell from the pic, but on the new cap, the seal doesn't sit low enough, definitely not a Stag item. The thing about self curing problems is that they tend to return, good luck with it. M

[V Mad]

The new one on the left looks more like the usual stag cap than the old one. Dont forget that items like this are made to a very low cost, and they are not precision parts. I buy a lot of these and I test them all; theres always a couple of rejects in each lot.
You need to remove the expansion bottle, and see why it does not fit. You can often bend the tags slightly to get a fit. Or just replace it with another cap.

[Stocky]

The last cap I bought had a seal that was marginally too small in diameter, thus hot coolant escaped and it took me a while to work out why.

[Richard Saunders]

Bruce, I have a spare 20 psi cap. The lugs look the same as the l/h version in your pictures. You're welcome to have it though if you want it. Just PM me your address and I'll pop it in the post.

Rich.

[Gresley]

I wonder if you have been sent a Triumph 2000 cap by mistake?