2004 1grfe mystery coolant loss

Hello,

I bought a SR5 4runner with a couple years ago and have had a longstanding issue with coolant loss I haven't been able to figure out. It started after the car heated up while slowing down after a highway drive, which lead me to replace the fan clutch, but I eventually realised the issue was the loss of coolant. Topping off the coolant fixes the issue for months at a time of city driving, but the coolant slowly and steadily disappears. The coolant seems to drop the fastest during highway drives, and after about 3 hours of continuous driving I have been able to add close to half a gallon to the radiator. The car has a new (within past 2 years) radiator, thermostat, water pump, radiator cap and fan clutch. I can't see visible leaks anywhere, and there are no leaks when I let it sit. I took it to a shop and had the cooling system pressure tested, and they reported no leaks. I thought maybe it could be HG, so I did a cylinder compression test and found excellent compression (150+-2) in all cylinders, and there are no other symptoms (no white smoke from exhaust, no milky oil, no rough idle).

After replacing the radiator cap and finding that I am still slowly losing coolant, I decided to come here as I am at a loss. Anyone have any ideas? Thanks!

 

Welcome to the forum.

If you have done all of the above with no noticeable leaks. It will probably be time to do a leak down test or a block test.
To get an idea of available options, search for BT-500 combustion, block test kit.

 

Also, a simple test would be the dye test in the radiator filler neck. The dye changes color when exhaust gasses are detected in the coolant. You'll know in seconds when you put the dye in at the radiator cap.

 

Sooo.... Not to be "THAT GUY" but you may be in for a bad time.... I've got a 1GR-FE that is about to get head gaskets and it started the same way.
I could go for weeks - if not months - around town with little to no fluid loss... but get that bad boy out on a 3 hour jaunt across the country side and I'd better had a jug of coolant with me.
Complete conjecture but it MAY slowly morph into hard rough startup and throwing a cylinder misfire code ... P0306 in my case ...

As others have said ... dye test your rig before it gets more expensive ... cause right now it may only be gaskets

At any rate good luck!!!

 

Thanks for the replies!
I tried the dye test today, and I was only able to get a few bubbles through but the fluid didn't change color. Looked nothing like the amount of gas that the youtube videos were able to get through, after the first few squeezes it stopped getting any gas through all together so I gave up on it. I did try the "glove test", and attached a photo with how that looked. It definitely didn't fill up the glove, but when I put the glove on flat I could see there was some pressure building up when I revved. Not sure if this is normal or sign of bad HG.

 

What did this rough startup sound like for you? Occasionally on cold starts It will crank normally and then sort of whisper/hesitate for a second before starting, but the rest of the time it starts right up.