| T O P I C R E V I E W |
| metallicpearl |
Posted - 02/06/2012 : 10:10:26
Good morning!
I have a question for those of you with mechanical car knowledge, if you'll entertain it!
Here goes...I noticed yesterday that there was a slight hiss coming from the duchess' expansion tank yesterday. I traced the sound to the cap and promptly bought a new one today. The thing is, I am normally able to squeeze the big radiator hose (sorry for the lack of appropriate terminology here) but after fitting the cap (hiss gone - w00t) and taking her on a good run, I physically couldn't squeeze said hose due to the amount of pressure. This was when the engine wasn't running.
Is this normal or should I be worried? I have no warning lights (yet) and I seem to have lost a very small amount of coolant, though I would have thought that this would be down to the fact that the gasket on the old cap is a bit knackered. Otherwise, the car is an noisy as it normally is for an old diesel and seems to run okay. |
| 4 L A T E S T R E P L I E S (Newest First) |
| metallicpearl |
Posted - 02/06/2012 : 10:55:04
quote:
Originally posted by Th0mas25
quote:
and usually the design of the cap is to act as a pressure relief valve should the pressure get too high
Indeed. It's quite possible the cap didn't need replaced, maybe it was just releasing pressure. If I were you I'd check the old cap to see if it's got a pressure release valve... and ensure that the new cap has that also. No valve = no release of pressure = rock hard hoses = well.... something will give at some point!!
Thanks for this.
I actually got an identical cap to the one that was fitted before. The gasket in the old cap has started to overlap the screw thread so I think it's had it  . |
| metallicpearl |
Posted - 02/06/2012 : 10:53:47
Thanks for your reply, Stakka.
I'll cross my fingers! I've got quite a few long journeys next week so I'm glad I've got RAC cover.
I have actually had heater problems and I ended up replacing the heater valve no less than 5 times in 6 months (I kept buying cheap parts...false economy). My oil cooler failed about 18 months ago and the coolant system was flooded with oil so I check my coolant at least twice a week - perhaps the constant on-off of the cap has contributed to its premature demise.
Thanks again. |
| Th0mas25 |
Posted - 02/06/2012 : 10:52:54
quote:
and usually the design of the cap is to act as a pressure relief valve should the pressure get too high
Indeed. It's quite possible the cap didn't need replaced, maybe it was just releasing pressure. If I were you I'd check the old cap to see if it's got a pressure release valve... and ensure that the new cap has that also. No valve = no release of pressure = rock hard hoses = well.... something will give at some point!! |
| stakka |
Posted - 02/06/2012 : 10:47:26
Some...but not necessarily all, hot water hoses should become quite pressurised - and usually the design of the cap is to act as a pressure relief valve should the pressure get too high. The hoses will probably also stay pressurised for a while after the engine is stopped whilst everything takes a while to cool down.
The previous cap may have blown though due to underlying problems, but only a slight chance I would say. Things like your car heating system playing up will also show underlying issues.
But if the car seems to run ok then you should be ok..... but you will soon know if all is not well when it blows up !
And obviously follow the golden rule in never removing a cap or hose when everything is hot or pressurised !! |
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