rstl99

2004 GX470 2UZFE 120,000 miles, purchased about 3 months ago. Timing belt and water pump replaced 4 years ago. Original rad and hoses as far as I can tell.
The coolant level in the overflow tank is dropping gradually. I noticed it was low after I bought the truck, I topped it up a few times and then it seemed to stabilize. After a highway run the other day the level was down again and needed to be topped up.
I've looked everywhere for a sign of a leak and can't find any (around water pump, hoses, sides of heads, rad, etc.).
I've replaced the radiator cap and no effect.
Maybe there's a pin hole leak somewhere that is allowing coolant to vent while vehicle is at speed, and leaves no traces?
No sign of head gasket failure (spark plugs are clean, blue fluid tester for fumes at rad reveals no exhaust gases present, no noticeable fumes in the exhaust). I know these 2UZFE engines are not known for head gasket issues.
A bit of loss is probably natural, but I've probably added half a gallon of coolant since buying the truck, to top up the level in the overflow tank.
Any ideas on where else to look for where the coolant is going? Should I replace the top and bottom rad hoses in case there's a pin hole leak in one that I can't see?

Forgot to say: my mechanic did a cooling system pressure test today and all was good. He's also the one who looked at the spark plug condition and checked all around the engine for signs of leaks.

chiph9

Are you still on the original radiator? I had to replace mine last year (also a 2004). The sign was that there were red crystals building up along one of the end caps. If you've got a pinhole leak in that area, it might be evaporating before crystals can form.

Otherwise - sounds like you've checked the usual things - no suspiciously clean spark plugs, no white exhaust smoke, no red spots on the garage floor.

Chip H.

rstl99

Thanks Chip. Yes, I believe it's the original rad still in there, and I'm starting to think along the lines you suggest, that I might be due for a new one, even though there don't seem to be any outward indication of it leaking. It would certainly make things less stressful for me (thinking worst case scenario ie. HG) to think it might be the rad... Maybe I should just replace it as a preventative measure (even though I know some people will say "I've driven 200,000 miles on my original rad and never had a problem")...

yackowski

I would definitely look for the red-ish colored crystals chiph9 mentioned before swapping radiators. Mine was clearly leaking below the radiator cap, along the end cap seam at 90k. Good luck to you though.. hopefully it isn't the heater core or anything mentioned on the other forum that requires dash removal- yikes!

Cole

bbrowncods

The anti-freeze is evaporating at the leak point under the heat and pressure. The best way to tell where it is leaking is to use a pressure tester while the system is cool. Any AutoZone or Advance will loan you one. Since the fluid will be cool, you will see exactly where it is coming from by where it is dripping on the ground.

rstl99

The mechanic pressure-tested the cooling system when the engine was warm and no leak was revealed.
He then left the system pressure-tested overnight and again no leak.
He says he's pretty confident there isn't a head gasket issue.
So where the coolant is going remains a bit of a mystery for now. I will stop fretting about it, and just keep topping up the overflow tank when it needs it and keep monitoring for possible leaks.
Yes, hopefully it's not the heater core or something like that...
Weird...

neub

you are asking for a crystal ball type of answer, so crystal ball answer you shall get. It's most likely your radiator. My radiator passed the pressure test hot and cold - didn't matter. I still kept topping off, ended up removing it to see that it's leaking in three different palaces at 150k. PO replaced the water pump some time prior to my purchase. He bough the cheapest pump possible that called for a FIPG - that's a bad idea. That was leaking. He never changed the coolant outlet gasket at replacement, that too was leaking.


If you have not done your timing belt yet, it's time. All those parts get removed as a part of the job. You will find the leak. Good luck

mswtoyota

I agree with neub, it is most likely the radiator. I've had radiators with plastic tanks on other vehicles pass pressure test hot and cold, but there was a pin hole or small crack (it usually shows up under where the top hose connects to the rad). Sometimes they didn't leak at all, sometimes they did. Last weekend found the rad leaking on a 2008 Grand Cherokee with 80K on it. Same thing: sometimes there was a puddle under it, sometimes there wasn't. Tiny trickle of a leak coming from under the upper hose connection (through the plastic).

BradTank

I know mine had the infamous radiator leak, and it was also a 2004. It was in the lower, driver side corner where the plastic meets the aluminum. You could see the pink crusty buildup at around 100k miles. Not sure why the pressure test didn't reveal it, maybe it wasn't at the right temperature?

I would go ahead and preemptively replace the radiator, it's not much more expensive than a new car battery. It's pretty clear that problem is widespread enough to indicate almost all of them will eventually leak. Not worth something like an overheating situation where you can really have some expensive damage.

rstl99

Well, consensus seems to point the rad itself as most likely suspect.
Funny, I would have thought a cooling system pressure test would reveal that, but maybe I misunderstood the purpose or characteristics of this test.
It would be a good idea to replace it (and the two main hoses) if only for good PM.
I'll educate myself on OEM vs good aftermarket rad's and prices for the GX470.
Thank you.

bbrowncods

Really need to put the pressure to the system of at least the cap pressure, and I go 5 psi more than that. Not really looking for a pressure drop as I am wetness at the weak points in the system (rad ends, hoses, WP, thermostat, etc. What the test will not check is the cap itself, the seal around the rad and cap, the hose between the rad and overflow tank. Even the overflow tank can have a leak.

rstl99

I've never done such a pressure test myself, so what you say are helpful hints If I do it in the future. Yes I also thought about the overflow hose and tank. Checked the hose and it looks fine, and will take a look at the tank itself for good measure.

Amboss72

Recently had my radiator, clutch fan and thermostat all replaced to the tune of $1100. My Gx had overheated and those were the items they determined in need of replacement. Took the Gx back to the shop to have Lexus coolant put back in the new radiator once it was determined ther were no leaks. Woke up the next morning to coolant all over my garage floor. Immediately took the truck back to the mechanic as I had driven the truck the night before with no problems. Mechanic says the water pump needs to be replaced as coolant is leaking out a "water pump seepage hole". Water pump and timing belt were replaced 20,000 miles ago. Does this sound right? Anyone have suggestions?

Goosed

wouldnt be the first time someone "replaced the TB and WP but actually didn't do anything and said they did"

tz693

Water pump is a big job. I would get a second opinion.