colin4989

Disappearing Coolant Ls430

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Hi all

Hope you can help!

I've had a dropping coolant level (even after the dealer has topped it up )

Been like this for over a year had it pressure checked by dealer about 3 times ( including at service)

It's done this before and after I had the timing belt and water pump changed

Any advice would be great thanks colin

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It has to be going somewhere.

Coolant reservoir pressure cap is one possible cause, a leaking heater matrix is another, head gasket failure is possible but unlikely.

These engines (well ay least the LS400s) can be notoriously difficult to completely bleed of air in the cooling system.

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Hi Steve thanks for the reply.

The pressure cap has been replaced

The dealer can't find anything wrong but as you quite rightly point out it has to be going somewhere and it is definitely dropping

Colin

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How much does it drop? My old RX would dump most of the coolant out of the expansion bottle, below the min, but then wouldn't drop any further. It was the same for all the years I had it, gave up topping it up in the end as it made no different - the rad was always full.

I would suspect there is a tiny leak in the rad. Worth making sure your transmission fluid is at the correct level and nice and red, you don't want to find out too late that coolant is getting into the transmission cooler which is located inside the radiator.

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Hi colin

Like yours it's the same thing. It's currently sitting just below min mark when engine is cold

Dealer said they checked rad out and no leaks

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Colin how do I check the trans fluid on the 430?

Hi Colin. I assume your vehicle has the 6 speed transmission? It isn't easy become there is no dipstick so you have to get under the vehicle, remove the transmission cover, remove the refill plug and then check the level comes up to the bottom on the hole.

The older 5 speed had a dipstick which you could use to check the level, and also use to syphon/refill the fluid.

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Colin thanks for the info

Not very good with that it sounds like I could break something

Will take into the garage to check

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the fluid shouldn't need to be replaced however a drain and refill every now and then is normally a good thing. You just need to make sure the correct fluid is used - Toyota WS I believe for your transmission but your dealer should be able to confirm. Don't mix different fluids and a standard drain will only replace about 1/3 of the total fluid within the transmission.

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Colin thanks so much for answering my questions, if I get Lexus to do it am I asking for a full flush and refill so all the fluid gets changed?

Thanks again

Colin

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I don't normally recommend using a flushing machine as that can disturb dirt in an old transmission that hasn't been flushed before and cause problems, although I doubt a Lexus dealer in the UK will have a flushing machine anyway.

I'd make sure they know how to perform a full change of fluid - it isn't something they normally do.

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Hi guys

Update. Put car into garage. They were aware of the probs with gearbox and coolant mixing with these models

They replaced coolant free and pressurised the system again and gearbox oil (at my request) and checked the car over thoroughly but couldnt find any leaks noting only that the gearbox oil that came out was slightly dirty but not contaminated or burnt. I use the Lexus garage (servicing and warranty etc) a lot and I'm confident that they have been checking it thoroughly.

Got the car mot(£27) at same with no issues woohoo

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