Pressurising Fuel Tank ?

[grey]

I've started to get a funny sound coming from the rear of the Chimp, it sounds similar to an oil can popping but louder. It's not all the time. Usually restarting after a short stop can set it off. Anyway, from looking back at the cars history this doesn't seem to be a new problem, and the service records indicates the tanks breather has been looked at to sort out the problem in the past. Has anyone ever heard of this sort of thing before and/or have a solution, or can someone point me in the direction of the breather, and how I can access it. Any help greatly appreciated, while we have a little good weather left. Cheers Graham < '96 400 HC >

[macca]

Very common - posted many times on this BB, its the walls of the tank expanding\contracting under pressure. Not sure how to fix it but wouldn't worry. Mine does it but only after starting within 20 mins or so of shutting down. Edited by macca on Wednesday 3rd October 21:52

[Neil Hyde]

grey ' see the thread on "Weird Noise" as to what happens if the filter isn't kept clear . The repeated expansion can lead to the baffles separating .

[philr]

As the boys say, this is a common "feature" and doesn't seem to cause any problems - other than briefly scaring the life out of you. I have discussed this with my dealer who stated that this is not a problem and is just down to the equalising of presures. First I've heard of it causing problems with baffles etc. I suggest that you ignore it and after a while you wont even notice it happening.

[KarenH]

quote:I suggest that you ignore it and after a while you wont even notice it happening.

If the petrol tank is frequently expanding/contracting that fiercely, it makes sense that the baffles will eventually over time work loose. Let's face it, the noise isn't just a little "pop" but an almighty BIG BANG - hard to ignore too. Your Chim's next owner will probably post a "what's that banging from side to side in my petrol tank" thread.

[.mark]

Isn't there a tiny breather hole in the filler cap that allows the presure to equalise?

[Neil Hyde]

Phil R . I would be interested to know which dealer you checked with . If that is the advice they gave you ,it is a place where my Chimp won't be going for a service .

[grey]

Cheers for all the advice. Although It is very hard to ignore, and if it may lead to separated baffles I want to at least try and do something with it. I've read elsewhere that the tank breather leads to a carbon filter "At the front" of the car, and if this gets blocked or filled with water it stops the petrol vapour from escaping and so causing the bulid up in pressure. Does anyone know where this filter is? With us all driving these 4-5 litre monsters I'm sure we're all very concerned about the enviroment but this aside would it be safe to vent the tank to atmosphere. It seems safer than Possibly having the tank split. Any more Ideas? Cheers Graham <'96 400HC>

[trefor]

The carbon filter is behind the front grille. Accessed by removing the grille on older models, not sure about post '96 cars, must be a hole in the engine bay?? I think there may be two types of bang being referred to here: - A light pop, loudish, but not frightening. Probably pressure equalisation and no big deal. They all do that sir. - A loud bang which is scaring some people (as mentioned by Karen H). This could be more serious. Trefor/.

[philr]

Neil Hyde,
I wont name this dealer other than to say that it is one of the dealers that is always quoted as being one of the top TVR dealers. I have always been very happy with this dealer and trust thier advice on this and other TVR related matters.
Incidentally, my Chimaera has not made this noise for a while now, so maybe it is something that was resolved at the last service - but I'm not aware of any work done to the breathers or tank.
Maybe my idea of a loud bang is different to that of other people.
If people are worried about this noise then they should get it checked out by a TVR dealer.
In my case, and other TVR owners I have talked to, this noise has been a "feature" rather than a problem.

[Neil Hyde]

Phil R .
The dealer who replaced my tank after the baffles detached does not have a particularly good reputation and put up a fight about replacing the tank . But when I collected the car the service manager also handed me the filter which was more like a sponge it was so wet . But what would I know ,I'm only an aircraft engineer !

[ATG]

It strikes me that these threads usually end with the conclusion that the problem is a wet breather filter. Surely replacing the filter has got to be a better option than potentially replacing the tank. Or have I missed the point?

[KarenH]

quote:
this noise has been a "feature" rather than a problem.

Like it! You're not a car salesman are you Phil?

[philr]

Sorry Karen, I slipped into software speak.

up until this particular thread I hadn't heard of a need to change the fuel tank just because of a bit of presurisation. I guess that if you have a problem gas presure in your tank then this can be nasty.
Gas isn't a problem I have any more. I do understand how embarising it can be for some people though, to make a loud noise as their gas pressure is released.

[grey]

Thanks again guys, and girls for all the info. It seem that I should start with the filter, which I now know is just behund the grill. Just in case I'm a complete idiot, what am I looking for? How big? shape? colour? Is it an oil filter type can or maybe an air filter type black box?

Sorry about all the questions, but I get worried when I pull apart my nice new car and havn't got a clue what I'm looking for.

I'd already thought about the hole in a the filler cap, is this a really bad idea? If I bought a nice shinny leven one, I could drill a small hole in my old one and try it. What do you think, daft idea or what?

Cheers

Grey <'96 400HC>

[trefor]

Daft idea. I think it would make sense to find the cause of the problem and cure it instead of bodging it.

If you do insist on trying this then why not drill the old gas cap - then if it all goes pear shaped you still have your Leven cap.

The carbon cannister is a huge mother of a thing - looks like a foam air filter element (ITG style) - you won't be able to miss it. There isn't that much stuff where you'll be looking. It will probably look a bit soggy and sorry for itself. Thing is, are you going to replace it? If so then have you got one to replace it with? (When I first got my Chimaera Henley replaced this under warranty and it cost £300 - I'm not saying the part costs that much, but be aware).

I'd really suggest getting an independent expert to look at the problem. You can mess about when petrol is involved.

T/.

[atg]

If anyone has any doubts about what happens when petrol catches fire, I suggest you take a tea cup full and pour it on the driveway. Stand back about five feet and start throwing lit matches at it. If you do this on a nice warm sunny day you'll probably find you are standing somewhere near the middle of a big puddle of flames. Petrol is f***ing dangerous. It is in a totally different league to fuel oil, parafin or meths. It forms puddles of invisible and explosive gas in any dips and hollows ... like the boot of your car ... given half a chance. Treat with caution.

[grey]

Thank again guys, Advice well taken. I'll get it looked at at the service.

Cheers

Grey