DanIrl

wow thats a pretty big leak, do you have any pictures of the offending pipes? Were they split or cracked?

FatherTo1

As far as my mechanic can tell, it was leaking at the entry pipe O-ring towards the front of the engine (like@Doublebase suspected), where the yellow arrow points to, and also at the rear of the valley plate seal (yellow circle).

It was leaking pretty good and coolant in the reservoir tank went from full to below Low line in four days, yet engine temps never rose, no smoking nor smells, and no drips or puddles underneath the car. There was no way to see the leak from above the engine until the late stages and only if you knew exactly where to look. I can see it now through a crevice from the top but could not see it at all a week ago, even with an endoscope camera. It was still Summer temperatures outside so I didn't use the heater yet but apparently that is a telltale sign of a leak if you don't get enough heat. Sometimes the AC blew too cold but I just proudly thought the system was working too well. I am just glad it wasn't a head gasket leak.

Doublebase

Mbbarron

Wow, sorry to hear about this coolant leak! Thanks for keeping the rest of us informed so we can look out for this type of thing. I'm learning so much from everyone on this forum! The quote from your trusted indy mechanic sounds pretty reasonable all things considered.

Kuhan

Thanks for a wake up call. Does the LS have a low coolant warning? I have to check the coolant level tomorrow.

FatherTo1

Not to my knowledge. I recall a post asking the same question and the consensus was no low coolant sensor or warning light.

Just being proactive and checking regularly should be sufficient, although I know it's kind of a hassle to remove all the paneling just to take a quick peek.

In short, here are potential symptoms:

-Coolant keeps disappearing, yet no drips or puddles under the car
-AC appears to work too well
-Lack of heat at idle or not enough cabin heat during cold weather
-Coolant stain near transmission (you can see this underneath without raising the car, but probabaly even easier to see for those with the air suspension and Height High option)
-Lastly, I haven't confirmed if this is actually related to coolant leak yet, but I notice a lot of crackling sounds when I turn off the car. I know it is common with the expansion of aluminum engines and contraction as it cools but I am curious if I'll hear less crackling sounds after my coolant leak is fixed. The LS 430 doesn't make any crackling sounds after it shuts down (well, maybe just one or two pings).

abs

Looks like I have a similar issue. Car has very low miles (about 17k now) but original owner did not maintain the cooling system and the second owner swapped the fluid with non-OEM. Bottom line, I have coolant running down over the rear of the passenger side valve cover and need to keep refilling the reservoir every few days. I do not know if the issue is just the o-ring or also the valley plate seal. Anyone have a good recommendation how to test it? I suppose I could buy a simple pressure test kit and try to isolate the leak.

jkittlesen

Good post Father to 1.

FatherTo1

Sorry to hear about your discovery, abs. If it is towards the rear then it probably is the valley plate. My O-ring was also leaking but you can see in earlier photos that it's a much smaller area up front and would be tough for the coolant to travel all the way back towards the firewall. Good job catching it early. Worst case is the repair bill is relatively modest and you can have the car back in two days time. I wish there was more I could offer to help. Hope it all gets resolved for you soon. Please keep us updated.

abs

FatherTo1:

Appreciate your reply to my post. I've just been researching this topic and specifically reviewed the photos you had posted as well as the shop manual. It appears that there are two coolant bypass lines (steel lines) which then connect to rubber hoses right above the rear passenger valve cover. I can see that the leak appears to be dripping down from above the valve cover itself, so I'm now suspecting this may be a somewhat different issue than either the o-ring or the valley plate. I will dig into this in the next day or so and see what I am able to determine and post back here. It would be better if this was in fact one of those coolant bypass lines I mentioned as I suspect it may be an easier repair. Also, I know for a fact that the prior owner had his local shop (not Lexus) do the coolant exchange, it would not surprise me if that shop messed around with those fittings to help bleed the system afterwards. Of course, I'm quite sure they did not have the shop manual nor did they realize that there was a bleed valve at the upper radiator hose connection to the radiator.

roadfrog

Reminds me of the dreaded "coolant pipe leak" found in the BMW 4.4 V8's. I had it in my 7 series BMW. It was a MAJOR job that was extreme drama to replace.....to the tune of 3-5k dollars.