Disappearing coolant - don’t know where it’s going? (1 Viewer)

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May 24, 2016
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Location
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So I noticed 2 weeks ago that my wife’s LX570 coolant overflow reservoir only had about a half inch in the bottom. It’s never overheated or had the temp gauge elevated - although we’ve only owned it 3-4 months. It’s a 2014 with 170,000 miles.

PPI was done at a Toyota dealership with an additional inspection done at a Lexus dealer a month after we bought it (2 months ago). Everything checked out and no mention was made of the cooling system.

Radiator looks fairly new and is not OEM. So I figured they just had not put enough coolant in. I filled the reservoir up and 2 weeks later it’s back down to just a half inch. I filled it up last night while the engine was still slightly warm and filled it up the the F. I let it sit overnight and the coolant is all the way down to the L line. (Pictures below). There are no signs of leaking anywhere around the radiator or on or under the reservoir. No signs of leaking under the vehicle or puddles of any kind.

I ran the engine and brought it up to temperature and the coolant level rose about 1” in the reservoir tank.

Hoses appear in good condition, the upper radiator hose is not collapsed and the radiator cap looks in good condition as well.

Coolant level inside the radiator is up to the very top, bright pink and looks good.

There does seem to be a very slight sweet Smokey smell coming from the reservoir side of the engine. It’s very slight but not what I’m used to smelling with either of my 100’s or the 80 that I’ve had. Definite not the smell of oil burning like you’d get with a valve cover gasket leak. I’ve never owned a vehicle with any radiator or cooling system issues or coolant leaks so I may just be missing something.

Any ideas of what to look for or where my coolant could be going?

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Had the same issue with my 2104 LC this year. Kept noticing the coolant was low. It was a valley leak.
 
Check all hoses for fraying and potentially dripping coolant but this sounds like a valley plate leak. If you have a borescope you can quickly confirm.
 
I was already planning on taking the 570 in for a full tune up and baseline. Was going to do water pump and thermostat, radiator and hoses ( if needed), heater T’s, serp belt and tensioner, idler pulley, fan support bracket and heater hoses, along with spark plugs and any other worn belts.

If it ends up being the valley plate, does it make sense to go ahead and have all the other stuff done at the same time? Anything else I should do while they have it pulled apart? PCV valve? Alternator?

Should I trust that aftermarket radiator or have that replaced with OE as well? Does the newer version of the radiator have a different part number and is that compatible with my ‘14?

I also saw there is a specific $$$ sealant to use when doing the valley plate. Is this different than what Toyota used?
 
Radiator part number didn’t change but the units delivered after late 2018 are the updated design. As for whether to change it preventatively.. that’s a tough one. Yours may go for 100k. Or it may not.

Yes check the above linked thread. Not too hard to get under the truck and look for evidence on the bellhousing. If nothing else top up the reservoir and monitor it for change.
 
Radiator part number didn’t change but the units delivered after late 2018 are the updated design. As for whether to change it preventatively.. that’s a tough one. Yours may go for 100k. Or it may not.

Yes check the above linked thread. Not too hard to get under the truck and look for evidence on the bellhousing. If nothing else top up the reservoir and monitor it for change.
Any issue with continuing to drive and top up for a week or two until I can get it into my mechanic?
 
Any issue with continuing to drive and top up for a week or two until I can get it into my mechanic?
Literally what I'd tell a family member to do if I couldn't check it out for them.
 
Any issue with continuing to drive and top up for a week or two until I can get it into my mechanic?

No problem - also please note that the coolant reservoir should be at the F mark when the engine is stone cold. When the engine is warmed up, the reservoir level will be above the F mark.

HTH
 
No problem - also please note that the coolant reservoir should be at the F mark when the engine is stone cold. When the engine is warmed up, the reservoir level will be above the F mark.

HTH
So, both times I refilled when engine was still warm. Yesterday I refilled to the F when warm and after about 5 hours sitting it was down about midway between the F and L. I let it sit overnight and it was down to the L (pictured above). But it appears to have stopped dropping. Engine is now stone cold and I've filled to the F line and it is holding steady and has not dropped anymore. I'll just keep driving it on my short 10 min drive to the office and monitor what goes on with the levels. It would be shocking to me to lose 1/4 gallon of coolant just sitting overnight without any evidence of a leak underneath.
 
So, both times I refilled when engine was still warm. Yesterday I refilled to the F when warm and after about 5 hours sitting it was down about midway between the F and L. I let it sit overnight and it was down to the L (pictured above). But it appears to have stopped dropping. Engine is now stone cold and I've filled to the F line and it is holding steady and has not dropped anymore. I'll just keep driving it on my short 10 min drive to the office and monitor what goes on with the levels. It would be shocking to me to lose 1/4 gallon of coolant just sitting overnight without any evidence of a leak underneath.
I am no mechanic, but can't it leak inside engine and get into the oil?
 
I am no mechanic, but can't it leak inside engine and get into the oil?
I’ve not heard of this on cruisers… but I think either you can see a problem when you open up the engine oil cap or the radiator cap. In my case both look totally normal. But I’m not very mechanically inclined either.
 
So, both times I refilled when engine was still warm. Yesterday I refilled to the F when warm and after about 5 hours sitting it was down about midway between the F and L. I let it sit overnight and it was down to the L (pictured above). But it appears to have stopped dropping. Engine is now stone cold and I've filled to the F line and it is holding steady and has not dropped anymore. I'll just keep driving it on my short 10 min drive to the office and monitor what goes on with the levels. It would be shocking to me to lose 1/4 gallon of coolant just sitting overnight without any evidence of a leak underneath.
Maybe whoever replaced the radiator did not get all the air bubbles out and when you began to top off the overflow tank the system slowly burped the air out? Once all the air bubbles have been removed, the coolant on the overflow tank will stop dropping. So keep an eye on it; if the coolant level holds steady, you can stop worrying about it.
 
Maybe whoever replaced the radiator did not get all the air bubbles out and when you began to top off the overflow tank the system slowly burped the air out? Once all the air bubbles have been removed, the coolant on the overflow tank will stop dropping. So keep an eye on it; if the coolant level holds steady, you can stop worrying about it.
Something similar happened to me. They replaced my radiator and the next day the reservoir was empty. But when I filled it back up it was good to go. I did not have to add a second time. The dealer thinks the original coolant in the reservoir was gobbled up by a void in the new radiator.
 
On my last oil service, the shop pressure tested the radiator cap and it failed despite the radiator only being 3 years old. It seemed to my eyes the coolant had been slightly dropping, but that stopped with the new cap.

Upvoting this as an easy and possible contributor.

It's normal for coolant to expand when the engine is hot. A weak cap will tend to let more volume out, and overflow the expansion tank. This can create more air pockets in the coolant system when it cools and contracts.
 
Start cheap with a good coolant purge/bleed. Also look at the back of your engine where it connects at the transmission. If it has wet/dry coolant then it's definitely the valley gasket. Good luck
 
If it turns out to be the Valley Plate leak, any other maintenance I should do that would save on labor? I've got 178,000 miles and most everything is still original except the newish radiator?
 
I’d do thermostat and water pump, probably hoses and possibly clamps too.
 
I have been battling a similar issue.
Owned a 2013 for a couple years now, noticed the coolant overflow tank was low soon after I bought it and poured some in there.
Checked a few days later and it was low again.
Rinse and repeat this process even after replacing the radiator / hoses and cap.

I still haven't figured mine out.
I've crawled under the rig with a flashlight and don't see any pink residue anywhere on the backside of the motor/bellhousing.

Need a borescope to confirm a valley leak. However I think it's unlikely with no residue on the bellhousing etc.
I'd rather not think about a head gasket issue, but not sure what else it could be once I rule out the valley plate.
 

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