robbyD

Yup, I can now sit back & enjoy this fabulous motor car! Of course we shall get the leak attended to & the whole LPG system checked over asap, but boy am I pleased

Panic over! The leak is coming from the LPG plumbing...and it's pretty easy to spot. Not impressed with Lexus & their Visual Safety Report. The job stated the car was loosing coolant & I was assured they would pay special attention to possible causes & that would include the LPG plumbing. Turns out, the leak was staring them in the face & they missed it.

There is still some air in the system then. As has been said, it can be difficult to get all the air out. The whole cooling system has a capacity of around 9 l on the GS430. Yes, I'll be looking at that next. Also, the system probably has a litre or two more with the LPG plumbing added. Thanks guys…the suggestions have been most helpful.

Thanks for your reassurance. What makes me a little paranoid about the coolant loss is the previous owner had it for just 5 weeks & during that time spent out on a full Lexus service, new Lexus rad, lambada sensor, wheel alignment & LPG regulator. He cited change of circumstances as the reason for selling & I've been a little worried that an expensive engine problem was the real reason. As luck would have it, I'm meeting up with a good friend of mine today who's up from Cornwall. He's a brilliant trouble-shooter and is getting a name down there as the go to guy for sorting out car & bike problems nobody else can. From what I've told him, he also thinks it isn't the Head Gaskets. Same goes for the ex-Lexus mechanic I use. There may not be an exhaust gas test but my man reckons his nose is a very good diagnostic tool :D

I've been wondering whether coolant is being dumped straight out of the header tank overflow. The rad doesn't have a cap, just a blanking bolt at the top, but a new header tank cap wouldn't be a bad idea, thanks.

Thanks Phil, but the Block Test I had done is the same kind of thing & it returned a negative result. I think the next step is to make sure the system is properly full with coolant.

Already checked the ATF & all looks fine. I was hoping to eliminate the possibility of internal engine leaks by analysing the exhaust gasses, but it seems no such test exists.

The rad was replaced about 3 weeks before I bought the car. I've been hoping the same thing, that the coolant level will soon stabilise...but after covering 850 miles & pouring in about 4 litres of Red, there's no sign of it levelling off. The car has been LPG converted and the Gas Regulator packed up & was replaced after the new rad was fitted…supposedly because of an air lock. I first noticed something was amiss when the heater blew cold & the LPG system wouldn't cut in. I found it odd that I could only get 1.5 litres of coolant into the system…I expected it would need more from those 2 symptoms. I've done around 100,000 LPG miles with the old GS without any problems. Occasionally had lowish coolant levels but that never affected the heater or the LPG system. The is a small amount of water "sloshing" from behind the dash when revved. I've been topping up the header tank with the engine running.

There's no white smoke as such, but quite a lot of vapour. It's difficult for me to gauge as the car does a lot of short journeys and it has been colder of late. To be fair, my old GS300 emits similar amounts of vapour…but no loss of coolant. I was wondering if the exhaust can be tested for the presence of coolant in a similar way the block test checks for combustion gasses.

Thanks, that's a nasty I didn't know about. Presumably Lexus would have checked the fluid when they gave the car a Safety Check this week but I'll have a look just in case. I did cook the engine a bit on my old GS300 when the rad failed but there was no damage done. Have a horrible feeling the same thing happened to the 430 and it also cooked the Head Gaskets or worse

My recently acquired GS430 is losing around 1litre of coolant every 200 miles. No obvious sign of an external leak. Engine Oil & Cap look healthy. Recent new rad fitted by Lexus. Block test was negative. Can the exhaust be tested for traces of coolant with a Gas Analyser?