LS460 - Failed Water Bypass Gasket

[OJWM]

Hi all,

At the weekend, my '07 LS460 was emitting a reasonable amount of steam from engine bay after a 2 hour motorway run (with engine temp creeping up in the short piece of town-driving after motorway).

Seems that a coolant leak had developed. Engine bay rather wet. Got a breakdown person out to it who was pretty confident that I have a failed Water Bypass Gasket. 

So I'm curious on a few fronts:

• Has anyone else experienced this?
• Would you advise I get anything else done at the same time this is being fixed?
• Breakdown person thought it was quite an easy fix - is he correct?

As a bonus, if anyone has any recommendations re: mobile mechanic services (Kent-based) that could help with this, that'd be amazing. Having a struggle finding any company that even answers its phones!

[Malc1]

Just as a starter .............  has the radiator been changed at 100k / 10 year intervals  ?  .......  as recommended on here !  ( date , mileage etc would help maybe )

Malc

[OJWM]

Believe radiator is original, so that's a great shout - thanks. Mileage is 112k and it's a 57 plate.

[Malc1]

there might of course be other issues .............  another Ls460 owner might pop up with summat useful

Malc

[steve2006]

I’ve never heard of one failing yet, assuming it is the front water bridge it should be a reasonable job once the plastics are removed, hoses off, 4 nuts.

If you want the gasket part numbers let me know 😀

[donkmeister]

On 3/14/2023 at 11:02 AM, OJWM said:

Believe radiator is original, so that's a great shout - thanks. Mileage is 112k and it's a 57 plate.

I did the rad on mine - it was a surprisingly straight forward job as I had very little in the way of corroded fasteners (the only one was a screw holding the rad to the a/c condensor at the bottom). I replaced the water pump, hoses and ATF cooler lines at the same time, and Toyota even helpfully explain the fill/bleed procedure on a sticker (on the header tank IIRC). Even with fiddly clips it was a summer Saturday's effort. Lexus quoted me £1k for the labour alone, hence the interest in doing it myself. 

If I were you, as a first step I'd refill the coolant then run the engine whilst watching to see where coolant/steam appears from. If it turns out you've just got a split hose or leaky rad then you'll spot that fairly easily. It's not impossible to have more than one leak at a time, but as you would need to fix them all anyway you may as well do the easier/cheaper ones first!

Also there is a YouTuber called Car Care Nut (who is a Toyota / Lexus mechanic of many years standing) has done a few videos on the LS460 when he has had them in his shop for various leaks... Suggest you look up his LS460 videos and see if you can correlate anything he shows with what you are seeing. I'll warn you in advance that he doesn't seem to rate the reliability of the LS460, don't take it personally 😁

[OJWM]

Thanks v much all for the responses (and sorry for my own belated reply)!

It turned out that the main culprit was the water pump. Got a mobile mechanic to fit gasket - he found that the pump is wobbly and was showing quite a leak...

Also had the radiator's 'nipple' decide it was time to shuffle off this mortal coil (I now understand it is infamous for doing so)...

So now I've sourced replacement parts, various necessary tools, the factory mechanic manual and watched various YT vids (incl car care nut) and am planning to replace parts myself on Fri/across the weekend 🙂

@donkmeister - I've bought hose pinch tools for the lower hoses going into the rad (which I understand are transmission fluid). Assume you replaced the fluid so didn't need to, but I don't want to enter into more complexity than I need to. Do you think I'll be OK with the pinch tools?

[donkmeister]

Yes, I was surprised at how little trans fluid comes out when the engine is off - it only pumps it round when the engine is spinning the transmission. The amount lost is not enough to warrant an ATF change as it's within the "margin of error" for trans fluid capacity. What I DID do after disconnecting each pipe was to immediately cover each pipe with a rubber glove held on with a rubber band to ensure no grit or grot got into the system.