Hissing

[alex.mcintosh]

Have been losing small amounts of coolant for some time and I now think perhaps it is evaporating from the expansion tank as occassionaly I can hear the hissing coming from the blue cap area. Have replaced the cap recently - anyone else's hiss?!?

Alex

[plipton]

Can you see/feel (carefully as it'll be a bit warm!!) anything coming out?

Could it be a split in the pipe between the tank and the cooling system? Mine gets reasonably hot (although I put in a slightly lower temperature otter as it overheated in the summer) but never hisses.

[alex.mcintosh]

Pretty sure it's not the pipe. The only other thing it could be is at the join between the neck of the expansion tank and the screw thread...although I have sealed this with liquid metal. Maybe a new expansion tank......

[chimburt]

the cap is vented - ie has a pressure release.
if you have topped up the coolant it is possible that it is just expelling excess coolant/ air bubbles

see the threads on cooling system and prepare yourself for some reading!

[plipton]

Silly question, but how full is the expansion bottle?

If it's too full then it could simply be that the cap is doing its job (albeit noisily).

The tank should be nowhere near full when the engine's cold.

Check the bible for full details (www.tvrbooks.co.uk). £33 well spent.


>> Edited by plipton on Tuesday 28th January 13:47

[alex.mcintosh]

The expansion tank is about 1/3rd full when cold, but due to the "evaporation" gradually gets lower and lower.

>> Edited by alex.mcintosh on Tuesday 28th January 14:48

[plipton]

Mine stays pretty constant (well it goes up a bit when hot, then back down).

Do the fans come on? is it overheating at all? what temp does the gauge say (not that they are all that reliable - mine says 75-80 degrees when the fans come on at just over 90).

If all else is OK then I would suspect a leak somewhere. Check the oil filler cap for mayonaise. I hope it's clean!!

So many questions..sorry

[Duncan Hermer]

getting out of mine a couple of weeks ago the garage filled with a hissing sound. My first thoughts of "puncture" turned out to be a slight split in one of the water hoses. Called AA next morning - he said he'd just fixed another Chim with the same problem - rubbing on the steering column and overtime just wears thin.

Slight water leak that i wouldnt have noticed had by garage floor not been totally dry and dusty. Hissing was very loud though. May be worth getting on a ramp and checking for leaks.

[cockers]

When you replaced the cap, did you buy from TVR or VW?

I bought a VW one and there was a washer missing, which allowed too much evaporation. Dealer spotted that at the next service and replaced it.

>> Edited by cockers on Wednesday 29th January 13:02

[alex.mcintosh]

I got the blue cap from a TVR dealer and have checked the washers - as per the last one....unless both are faulty!

The noise is definitely not coming from a split hose, but the top of the expansion tank.

No problems like overheating, head gasket, etc....

[plipton]

My header stays about 1/2 full (natural level). The bible says the natural level can vary between cars. Maybe yours is much lower. (shpub's is 2" below the top)

Does the tank ever run completely dry?

Have you bled the system to remove air locks? these might couse more pressure and blow past the pressure cap.

[dannyboyo]

Just a stupid question!! But do people put water in aswell as Coolant/Antifreeze. So far I've just been topping up with Antifreeze, which I don't suppose can hurt at this time of year, but I presume water can go straight in too!?!

>> Edited by dannyboyo on Wednesday 29th January 14:12

[plipton]

dannyboyo said: Just a stupid question!! But do people put water in aswell as Coolant/Antifreeze. So far I've just been topping up with Antifreeze, which I don't suppose can hurt at this time of year, but I presume water can go straight in too!?!

>> Edited by dannyboyo on Wednesday 29th January 14:12

I don't think antifreeze is that brilliant at transferring heat from one place to another. I think of you ran 100% antifreeze you'd probably overheat in the summer.

Personally I mix it first in an old antifreeze bottle and keep that in the boot for topping up (about 1/3 AF to 2/3 water - but it never really gets cold enough to freeze down here!)

[alex.mcintosh]

If I don't keep a close eye on it, the expansion tank does run dry. Originally there were no air locks, but when the expansion tank does get empty, I suspect air is then drawn into the swirl tank. Vicious circle really....

[plipton]

I can't fathom it - it really does sound like there's a leak to me or the level should settle down in the expansion tank.

I'd suggest doing a full check on the cooling system - water pump, pipes, otter, fans, rad, heater matrix...the lot. This might reveal the problem.

[ABBTVR]

plipton said:
I'd suggest doing a full check on the cooling system - water pump, pipes, otter, fans, rad, heater matrix...the lot. This might reveal the problem.

FWIW Usual leak tester is soapy water!
Just "Splash it on all over" and look for the bubbles. Would advise keeping it off the electrics though.

Big Al.

[Beano500]

alex.mcintosh said: If I don't keep a close eye on it, the expansion tank does run dry. Originally there were no air locks, but when the expansion tank does get empty, I suspect air is then drawn into the swirl tank. Vicious circle really....

Hmm!? On my Griff, when the coolant level starts to fall I pretty soon find that it won't idle happily. Symptom, I believe, of getting an air lock into the system just where a sensor is, hence ECU goes AWOL.....

.....topping up always seems to cure it immediately.

[shpub]

plipton said: My header stays about 1/2 full (natural level). The bible says the natural level can vary between cars. Maybe yours is much lower. (shpub's is 2" below the top)

Does the tank ever run completely dry?

1. That was on one of the TVRs I have had. Current Griff runabout is a 2 inch from bottom of tank'er.

2. If your head gasket has gone they will run dry as the water either becomes mayo in the sump or gas in the exhaust. Might be worth checking. Also if a gasket is going gases can pressure the cooling system and dump the water. A hydrocarbon check will confirm this. Available from Frosts if you don't fancy it yourself.

steve
www.tvrbooks.co.uk

[ribol]

You can get the cooling system pressure tested by any decent garage, should not cost a fortune. Sometimes there can be a leak that you cannot see, the pressure test forces coolant through the same spot. If they are not familiar with TVRs it may be worth pointing out that the rads cannot take too much stick!

Ivan

[alex.mcintosh]

Have had several pressure tests done by dealer and a hydrocarbon as well - all OK apparently. Due for a service in a few weeks...maybe same tests AGAIN! If all is still OK maybe I'll put it down to just one of those TVR things!