2001 Tundra Coolant Leak. Please help!!

Hi guys,

I recently changed my passenger side upstream (bank 2, sensor 1) o2 sensor. When I was replacing the sensor, I noticed some dried coolant on the sensor and some around the area. I followed the leak up and it seems it's coming from the upper top of the engine. The coolant also seems to linger around a bolt that is acting as a ground for some wiring (see pics). From the perspective of looking at the engine bay, the leak seems to be coming from behind the passenger valve cover. I basically need help identifying where specific the leak could be coming from. I just noticed the leak today as I was replacing the o2 sensor. I never noticed any white smoke coming from the engine and my temperature gauge has remained neutral. I also topped off the coolant reservoir a couple of months back and now noticed the reservoir is low again. I included pics hoping these would help. I would appreciate any help or feedback! Thank you!

Dom

 

Yes, I believe that leak is covered in this thread, which I'll give you a biased "you should read that" note about. Specifically, this bullet point:

• Coolant leaks: Three common causes: One is the is the gasket behind the thermostat housing, another is the coolant crossover at the rear of the block, and last but not least, old radiators is another source. Here's a list of things to check if you're losing coolant. For repairing the leak behind the t-stat housing, check this out. For the coolant crossover tube issue, you'll likely find coolant at back of the block, near where the trans and engine meet, check this reply for video/fix. For radiator leaks, this is one example of a tiny one - always replace with Denso brand, and know different cab types use different sizes. Proactive radiator replacement is smart. The transmission line routes through the bottom of the radiator, go look up "pink milkshake", it happens in these trucks.

That's the first place I'd look, and if you haven't checked that thread, I'd go for it.

FYI, that K&N intake/filter probably isn't really doing much for you except power loss and introducing more fine particulate into your engine. I'd personally revert back to OEM for the longevity of your engine.

Welcome to the forum!

 

Hey there, Dankydom
I would recommend using black light Dye in to the Coolant system! Then let the Engine get to operating temperature, then turn off the Engine and get the Black Light out and start looking around the back of the engine block and the crossover tube!
Then I would get a telescopic Mirror and shine the black light on the mirror to the hard to see spots!
Good luck!

 

Looks like the rear crossover. You will have to lift the manifold up to get a better view.

 

Thank you guys so much for all the ideas!! At least now I have an idea of where to start. After watching that crossover tube video, I'm certain it's more toward the back end of the tube. Now, I gotta find a vid on how to get the upper manifold out. Thank you!

 

Make sure you keep you fuel rail intact when you disconnect the manifold. they don’t have to be disconnected. I went with the first video I saw and went all in. I had a leak in the front crossover.

I found more videos when I looked up the engine vs the model and year

my leak
https://www.tundras.com/threads/coolant-leak-bypass-pipe-o-ring.81275/

 

Definitely listen to @jerryallday he's been there, done that! You're awesome Jerry!

EDIT: Just realized my link actually goes to that same post. You're the reason I ended up dropping that into the 'so you just bought a tundra....' thread.

 

Thank you! I'll definitely keep that in mind. Thank guys a lot! I really appreciate it!

 

Hey Jerry, since you have had experience with this issue before, do you this it's possible the leak could be coming from the engine block itself? I've just been going down a rabbit hole of tundra coolant leaks and now I'm fearful it might be a blown head gasket or something.

 

I know this isn't directed at me, but I'll tell you this: I highly doubt it's a blown head gasket.

We've also seen leaks at the front of the block end up at the rear of the block and draining out by the transmission: https://www.tundras.com/threads/truck-pissing-fluid.124677/

We've also seen freeze plug leaks: https://www.tundras.com/threads/freeze-plug-replacement-1st-gen.121644/

And even a mystery leak I don't know that we ever solved: https://www.tundras.com/threads/coolant-leak-near-trans.117883/

The best thing you can do for yourself is try to isolate the source of the coolant - go to the highest point where you see coolant. Take pics. Bring it back and post it, maybe we can help you. We've seen a shedload of various leaks on here, and never once has it been a head gasket.

 

Man thanks a lot. I think I’m just panicking at this point. The highest point seems to be at the location where I took the photos at the corner behind the valve cover but I can’t really tell unless I get the upper manifold out. Once I get it off sometime this week, I’ll come back with pics. Thank you!!

 

Totally welcome. Fingers crossed it's something simple. Your truck is at the age that it wouldn't be unheard of for that rear coolant crossover pipe's seals to be shot, it's probably not a bad idea to get in there and do it proactively. OEM part is not expensive. Install doesn't appear hard. Just heed Jerry's advice. You may just want to pick up the parts at the stealership ahead of time (before you pop things off) and do it while you're in there. But *do* check links in the bullet points list in reply # 2. It'll give you some other places to check for evidence BEFORE you dig in.

I'd recommend new intake gasket too, but learn from @bmf4069's experience: Don't buy an aftermarket gasket, his blew out in no time flat. I'm a huge FEL-PRO guy but I've been going OEM after seeing history with other vendor gaskets. Your earlier model is diff't from mine, I have a nice, rubbery press-fit gasket on mine

 

Yeah, I don't even see the ITM brand in there anymore.



But yes, beware cheap gaskets. They WILL break. I'm just glad the blew out and didn't implode.

 

If the leak is at the coolant pipe o-ring it will drip into the valley and out the drain hole under the starter. It could also be at once or the rear coolant crossover pipe gaskets at the back and then it will run down where the bell housing meets the engine on one side or the other

 

UPDATE: I wasn't able to get the whole upper manifold off but I did manage to take off the air cleaner assembly and loosen the throttle body. Taking off the air assembly helped me realize there is another leak (see pic). This leak is above the left timing belt and directly below the throttle cable. Maybe this is where the leak is originating and just flowing down. However, it does not seem like there is any coolant leaking into the valley. Either way, I still gotta take the manifold off.

 

You don’t need to separate upper and lower manifold

 

That’s the front crossover leaking

 

Pretty sure that's the 1st"oddball" leak I listed in reply #10 above - leaking from front to rear.

 

Hey guys,

I think I'm gonna come back to this project later. I put everything back together, topped off my coolant, and rode around the block for a while. I come back to inspect my engine and no new coolant leaks nor did my coolant reservoir go down. I'm guessing it's a seep coming from the crossover. I just don't have a lot of time right now. For now, I just gonna by some coolant dye and when I have more time I'll come back to see where the leak is originating. Thank you, guys, for all your time and help!!

 

I had one of the gaskets at the rear crossover seeping last year shortly after doing the TB and WP. It was losing 1-2 inches from the overflow reservoir per month. I bought the parts and for the past couple months haven't noticed any further losses so I'm just sitting on it as well.

 

I remember we had someone on here who simply pushed the tube in firmly on both sides and it quelled the leaking. The gasket was shot and that made the tube become unseated a hair.

 

That might be my issue. Just remembered, the last time I topped off my coolant was when I did my last oil change which was in January lol. I'm gonna be doing my oil change this weekend so I'll just be tracking the coolant reservoir from here on out