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Vapouriser leaking coolant?

 
 
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iansoady
Just got MTs


Joined: 01 Feb 2006
Odometer: 101
Location: Birmingham



PostPosted: Sat Sep 05, 2009 2:36 pm    Post subject: Vapouriser leaking coolant? Reply with quote

I have a 1993 3.5 v8i Disco with a Landi Renzo single point LPG system - fitted 7 years and 70,000 miles ago when I bought the car. It's been absolutely fine up to now.

Recently I seem to have been losing coolant. Oh no, I thought - head gasket. However, it's also been running a bit rough on LPG. It's also been reluctant to go above 4,000 rpm although may have been like this for some time, as I've never found this necessary anyway.

On a wild hunch, I thought I'd try it just running on petrol - did about 50 miles and no loss of coolant at all. Then about 10 miles yesterday on LPG and the coolant level dropped an inch or so.

It seems to me that perhaps the coolant is escaping via the vapouriser - is this possible / likely? I've pulled the plugs out and they're all a nice fawn colour with no sign of any being "washed" by water from a head gasket failure. The expansion tank isn't being pressurised any more than I would expect, and the engine oil is lovely & clean.

Opinions very welcome.

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Ian.

2001 Disco ES TD5 in Epsom Green
2004 Triumph Tiger 955i on adrenalin.....
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Rossko
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Joined: 23 Jan 2007
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PostPosted: Sat Sep 05, 2009 10:05 pm    Post subject: Re: Vapouriser leaking coolant? Reply with quote

iansoady wrote:
It seems to me that perhaps the coolant is escaping via the vapouriser - is this possible / likely?


It's possible, not especially likely but does it does happen.

Depending how the vaporiser is constructed, there's more than one failure mode.
Actual failure could be internal or external gasket, obviously; but occasionally the castings pinhole. Propane is an excellent solvent and can apparently leach out impurities in the monkey-metal castings.
Either way, pinhole or gasket, failure may seem to come and go.

Communication can occur between water jacket and LPG tank pressure - as LPG runs around 15 bar this will overpressurise the water system while running gas. Water may leak the other way when not on gas ; or it might not! Strangely, you'll rarely smell gas in the header tank - it seems hot water soaks up the odoriser.

Or, communication can be between the water jacket and the low pressure side. On a single point system, this is more likely to leak when running on petrol as the manifold vacuum gets applied, instead of the more or less atmospheric gas pressure. There wouldn't be much trace of a small leak in this manner, though you can check for condensation in the gas hose.

The most common leak is an ordinary external seepage at the water elbows on the vaporiser, or at the the tees into the original hoses; these can be hard to spot.

At 7 years old the vaporiser is almost certainly life expired anyway, so maybe replacement is a good bet - but do have it set up properly.

good luck, Ross K

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iansoady
Just got MTs


Joined: 01 Feb 2006
Odometer: 101
Location: Birmingham



PostPosted: Sun Sep 06, 2009 2:50 pm    Post subject: Reply with quote

Many thanks that's helpful.

Just been for a short run on petrol with no coolant loss, so I've taken the vaporizer out of the cooling system loop and will run on petrol for a week or so to monitor.

I may try running on gas without the coolant connected - is this possible or is it likely to cause problems? I never (well hardly ever) have any issues running on LPG even from stone cold in the winter so suspect the LPG doesn't actually need the water there to vapourise. Or is this just wishful thinking?

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Ian.

2001 Disco ES TD5 in Epsom Green
2004 Triumph Tiger 955i on adrenalin.....
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Rossko
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PostPosted: Mon Sep 07, 2009 7:51 am    Post subject: Reply with quote

iansoady wrote:
I may try running on gas without the coolant connected


Wishful thinking. It doesn't need to be hot but it does need to be stopped from chilling as the evaporating gas sucks out the heat...

You will get 2 or 3 miles and then stall in a strong smell of gas. The vaporiser chills until it reaches -40C internally, whereupon the liquid fuel gets through into the still-warm pipework and expands into waaay too much gas, flooding the engine and spilling out of the air intake. Open the bonnet to see the vaporiser in ball of frost.

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iansoady
Just got MTs


Joined: 01 Feb 2006
Odometer: 101
Location: Birmingham



PostPosted: Mon Sep 07, 2009 8:38 am    Post subject: Reply with quote

Yes, I kind of thought that might happen - like on the odd occasions when I've tried to run on gas in very cold & humid conditions.
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Ian.

2001 Disco ES TD5 in Epsom Green
2004 Triumph Tiger 955i on adrenalin.....
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