Help finding the source of a coolant leak

I am trying to track down a coolant leak on my 03 Tacoma 5vz-fe with 115k miles.

I first noticed a few drops on the mechanical pulley tensioner at the bottom of the engine. I had to do my valve cover gasket and decided to take a deeper look and find the highest point at which I can see evidence of a coolant leak. I can see dry crusted red stuff as far up as the camshaft position sensor bracket located at the front of the engine behind the black plastic cover. However I can't see anything else in this area as the source so I am stumped. Everything is covered by this black sheet metal piece behind the large cam pulleys.

-The water pump was replaced along with the timing belt 15k miles ago with OEM and does not appear to be leaking around the seal or directly below it
-The throttle body (2 rubber hoses) were not leaking
-The top central coolant hose was not leaking nor was the gasket where it enters the engine
-I saw no coolant pooled under the intake manifold on top of the engine
-No coolant at the rear of the engine as far as I can tell.

I understand there is a "bypass pipe" that runs around this general area?

Any ideas?

 

Yeah the bypass pipe runs in the valley between the heads and can be inspected by pulling the lower intake manifold which is going to require the fuel rail to be removed with it unless you can get a tiny camera in there from the front or back covers at the end of the valley where there’s some insulation. Pulling the intake isn’t too bad though and the fuel rail doesn’t need to be removed separately I think - ie it can remain on the injectors and be taken off along with the lower intake. Look up how to’s on replacing knock sensors - it’s like the same procedure.

 

Is it possible that coolant can leak from that bypass pipe area to the front of the engine? From my research it looks like people mostly see the leaks in the rear when it leaks there.

I don't have a small camera but I already have the whole intake off so it's only one more step to remove the lower intake manifold I guess.

 

The fast easy way is with a Cooling system Pressure tester !

Makes trouble shooting so easy! I use mine often.

Most parts stores loan or rent these out.

Good luck!!

 

Yeah it would most likely fill up the valley and drain out the back if you kept refilling it.

 

I found the coolant leak - it appears to be the coolant bypass pipe that runs under the lower intake manifold. There is red crusty stuff everywhere.

It looks like I need to order:
-Bypass tube gasket
-lower intake manifold gaskets (2)
-coolant

I am having a hard time finding the bypass tube gasket. Is it FIPG or an actual gasket? Would it be a bad idea to make a gasket for this instead of using the problematic FIPG again?

 

See post 6 - Dirty Pool has a deep knowledge of these trucks and I resealed mine w/ RTV when I swapped an engine and it's been doing good.

https://www.tacomaworld.com/threads/smoke-coming-from-back-of-engine.716853/#post-25513256

 

Post 6 is my post? Or am I missing something?

 

Sorry - check the link I forgot to put in there

https://www.tacomaworld.com/threads/smoke-coming-from-back-of-engine.716853/#post-25513256

 

@c0bra here's a video of the install on that from a guy that only follows the FSM in his videos:

https://youtu.be/_G_zqDC9kFM?t=254 if you click it, it should go right to the part, but if the link isn't linking to that time, it's right about 4:10

 

Oh I've seen this dude's videos. Thank you!!

FIPG is just silicone? Or is it something special? I have had good luck using Yamabond and Permatex also sells some cooling system specific sealant. https://www.permatex.com/products/g...mp-thermostat-rtv-silicone-gasket-maker-5-oz/


Also, another question...

Since I had to remove the fuel injectors to get to this point, I want to replace the seals since they will possibly leak if I reuse them. I found this kit - https://theinjectorshop.com/product...ter-seal-kit-for-toyota-tundra-3-4l-2000-2004

Any other suggestions?

 

FIPG (Form in Place Gasket) is Toyota's own "brand" if you will, of RTV.

I use Permatex.

Looks like a pretty good deal. I had found these when I had my engine apart but I think you found a better one.

Fel-Pro Fuel Injector O-Ring Set - ES70600

https://www.oreillyauto.com/detail/.../v/a/8218/automotive-truck-1998-toyota-tacoma

 

I purchased new OEM gaskets, factory coolant, as well as the fuel injector seals from the link I provided above.

I did a bunch of research on sealants, and apparently the correct FIPG for this joint exposed to coolant is Toyota 1282b (as opposed to the common 103 type), which is costly and hard to find. I will be using this, which is a specially designed RTV for ethylene glycol contact with a plenty high temperature rating: https://www.permatex.com/products/g...mp-thermostat-rtv-silicone-gasket-maker-5-oz/

Still somewhat tempted to make a gasket and use that in conjunction with the RTV but maybe I will just stick with the RTV only as it did last 100k miles.

 

While you are in there replace the knock sensor harness. It is an known “issue” sometimes and is cheap enough to replace.

 

$50 for the harness! PN

$45 82219-34010 is Compatible with Toyota 4Runner, T100,Tacoma,Tundra

82219-34010

Do they normally break at a certain point I can inspect? It looks fine to me but.. don't really want to tear this apart again especially with the cost of those gaskets.

 

Two things:
1. While removing the knock sensor harness it broke in my hands. Both connectors broke and the wires were rigid and brittle. Easy decision there...

2. Upon closer inspection, it was not the bypass pipe after all. It appears to be the intake manifold gasket. I was really worried it was the head gasket, but you can clearly see the stream of coolant from up above. I just hope it's not both the intake AND head gasket.

 

Was it the original gasket?

 

Yes, from 2003.

 

I keep looking at my photos and second guessing. There is clearly a leak at the intake port that has been dripping down, but by golly there's a lot of buildup around that head gasket. Coincidence? What are the odds of it being the HG at the same time? I don't want to do that job if I don't have to, but it would suck to put it all back together and still have a leak.

That said, this is probably the easiest type of leak that could be fixed with *gasp* stop leak *gasp* because it's just an external leak and not going into the cylinder.

 

Do a compression test while you've got your engine apart. O'Reilly's rents the tools as well as other parts stores for free.