Coolant Leak - Need Help Finding

[BigMike18]

Hello all, I recently found a pretty significant coolant leak in my 05 4runner 2UZFE with 249,500 Miles on it. I've attached some photos below of where I'm seeing coolant leak out, but I'm wondering if its a more serious area like the water pump based on how much I'm losing.


I fully filled up the coolant reservoir (from empty) around 3PM yesterday, drove 2 mins then sat for a 8 hours then drove 2 mins back and I go out today around noon to check it and completely empty.

For reference ive done the timing belt and water pump whole kit around 3 years ago (228,500 miles) and had no issues since, radiator was replaced last year and my main suspect right now is this upper thermostat housing combination leakage of both the o ring circular outlet and RTV gasketed water pump square part.

In a perfect world id much prefer that than to tear down the entire front end just to find out I gotta do the water pump again. Is there a way to rule out any possible leak spots. I considered taking the timing cover off for a better view at the pump itself.

Any help on this would be great.

P.s. The car has never overheated while under my ownership and never goes above 190F even on the hottest summer days.

 

[changed]

Do you see the coolant on the ground under your car?

 

[BigMike18]

Do you see the coolant on the ground under your car?

I mostly park in grass/sand area, but when I do park under concrete there is a medium sized pooling of coolant, more than a few drops but less than it all coming out at once

 

[rdruss]

IMO, whatever you have to do, you have to do! Yes, I'd pull the timing cover off to get a better look and then make whatever repair deemed necessary, you can't be losing that much coolant and feel comfortable.

 

[Hungryhawk]

I had a replaced water pump& timing belt on my Pilot start leaking at 20,000 miles because I let a shop select the brand! Obviously lower quality.
Had a premier shop redo belt & water pump with top brand (forgot names of brands).
Your pink deposits are surely coolant escaping. I would do the easy stuff first and keep a close eye on your engine oil for signs of dreaded coolant intrusion.

 

[BigMike18]

The teardown has begun.


Went out today and there was a pretty significant puddle underneath the front engine cross member. I drained radiator and began trying to take off as little as possible to rule out possible areas of leakage.

I attached some more photos below if anyone with more expertise would like to chime in. I see patches of crusty pink coolant residue but nothing that makes me say yeah thats the spot for sure.

 

[BigMike18]

Realizing now that I'm not 100% confident in a leak area I should have pressure tested the system using distilled water first... Would that help eliminate a majority of concern areas?

 

[BigMike18]

Current solution so I can drive and hopefully diagnose further over weekend is
Putting everything back together
Resealing upper thermostat housing with new FIPG and OEM O-ring (Part #16323C)
Refilling coolant with Peak Asian vehicles coolant and watching overflow reservoir meticulously over the next few days, multiple times a day.

 

[BigMike18]

So now 9 months later I have a coolant leak at the exact same spot as before. I believe this is more pointing towards the O-Ring and maybe a little bit on the gasket itself.

So before I had use an OEM O-Ring and actually not exact Toyota FIPG but Permatex thermostat housing gasket maker (dont use it is not as good as the actual FIPG stuff).

Below are the conditions of the O-ring and the gasket surfaces, I tried my best to clean up with a chisel and a box cutter blade.

My concern is that this is just going to leak again from that O-Ring spot it was in the same condition as the OP photo where the O-ring is jutting out a bit from the seal point and torn up. It seems there is a slight bit of plaque buildup or something of the sort on the inside of the o-ring connection point.

What should I do to ensure a smooth reinstall process at these two point.

 

[BigMike18]

I was able to find this in the service manual, but wanted to hear some experiences people may have had with this method.

 

[Jcmeadows82]

In the OG post, you shared 3 pictures. In the first 2 pictured it looks like the O-ring is popping out of the O-ring stay and smunched/possibly moved between the two metal components. Also I see what LOOKS LIKE might a gasket maker/silicone gasket material being used the last time this was opened? Maybe? I would strongly advise against anything but the OE gaskets, O-rings, and seals.

To be more certain of success, when you put all of this back together, make sure you replace all of the gaskets and O-rings with Toyota (or other high quality I guess...) OEM replacement components as well as replace the fluid with the correct coolant. Not all coolants are compatible with the 2uz. Usually the coolant is "Asian Pink" or something like that. With the O-rings, use a very small amount of some silicone grease on them to ensure they slide in without damaging or moving the O-rings.

*Edit
Really need to clean remnants of old gasket/O-ring off all of the mating surfaces and make sure none of the edges are sharp/rough. if you do any fine sanding of surfaces, just make sure you stuff a rag or something in the holes to keep junk out of your engine. You can get fine wire wheels that you attach to a rotary tool or drill. don't use any wire wheels that are too abrasive, just enough to smooth out the mating surfaces and remove junk. If you can remove components with flat surfaces, grab some fine sandpaper (220 or finer), place the sandpaper on a very smooth/flat surface and sand the components.

Additional note:
I did a timing belt/water-pump (shameless plug for my writeup in the how-to section of the forum... XD) and made the mistake of NOT using silicone on the O-ring for the tube that goes from the front to the back at the top of the motor, put it all back together and had a massive leak... was a mistake I wont make again with O-rings...