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Coolant system pressure test

Old 05-15-2019, 05:29 PM
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Coolant system pressure test

Hey everyone.

I've noticed a bit of a coolant consumption issue with my truck (3VZE) and performed a test on it this afternoon.

I put the FSM specified amount of pressure (17.1 psi) into the system via the radiator and could hear a hissing sound coming from the top-front-driver side of the engine and the pressure fell rapidly. More or less, where the arrow is pointing in this photo ( https://imgur.com/moNad93 ). I didn't see any liquid coming out, the sound seemed to be air. The engine wasn't completely cold, but it wasn't warm/hot either. I started up the truck and watched the exhaust vapor for anything unusual, but there was nothing visible coming from the exhaust. I let the truck warm up and ran the test again. This time, the system held the pressure @ ~ 17.1psi with a very small, gradual, drop in pressure (like, a 1psi drop over the course of 10 mins). I noticed a small amount of moisture at the base of the radiator on the passenger side, which seemed like it was probably coolant escaping.

Aside from probably having a leaky radiator, can someone help me understand what is causing this difference in results with the engine warm vs. cold? Do I need to investigate the source of the pressure leak when the engine is cold?

Thanks in advance for any insight.
JB
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Old 05-15-2019, 05:33 PM
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I can't open your photo, company firewall blocks it, but I would say your coolant was low when you first tried the pressure test, Air will move faster through a hole than coolant.
If you are sure you have a leaking radiator you will need to fix that and recheck to see if you have any other leaks.
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Old 05-15-2019, 05:35 PM
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Here's the pic
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Old 05-15-2019, 06:22 PM
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Temperature = expansion ( hot ) or contraction ( cold ). Check for a loose clamp or bad hose at where your arrow is pointing. If all clamps are tight when cold they should not leak when hot. That is considering hoses and connections are in good condition.
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Old 05-15-2019, 08:08 PM
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Your arrow is pointing to the hose from the throttle body, which turns and fits onto a tube that points straight up from the intake manifold. On my truck, that tube has some corrosion under the hose. Mine doesn't leak, but if the corrosion gets a lot worse it probably will. I would look closely at that connection.

If you're tempted to replace that hose (why wouldn't you be!), don't try stock auto parts store hose. It's a formed hose (16281-65010), and stock hose would kink if you tried it. Less than $12 (but plus shipping) from an online dealer.
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Old 05-15-2019, 09:25 PM
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Originally Posted by scope103 View Post
Your arrow is pointing to the hose from the throttle body, which turns and fits onto a tube that points straight up from the intake manifold. On my truck, that tube has some corrosion under the hose. Mine doesn't leak, but if the corrosion gets a lot worse it probably will. I would look closely at that connection.

If you're tempted to replace that hose (why wouldn't you be!), don't try stock auto parts store hose. It's a formed hose (16281-65010), and stock hose would kink if you tried it. Less than $12 (but plus shipping) from an online dealer.

Thanks, scope. I took a close look at that connection today and mine is definitely not looking great, I'll snap a photo tomorrow and show you. My question would be that since the tube, coming up out of the manifold, is badly pitted/corroded, is replacing the hose alone going to make a difference? Do I also need to sand that area to try to remove some of the roughness and improve the seal?
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Old 05-16-2019, 08:30 AM
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Originally Posted by scope103 View Post
Your arrow is pointing to the hose from the throttle body, which turns and fits onto a tube that points straight up from the intake manifold. On my truck, that tube has some corrosion under the hose. Mine doesn't leak, but if the corrosion gets a lot worse it probably will. I would look closely at that connection.

If you're tempted to replace that hose (why wouldn't you be!), don't try stock auto parts store hose. It's a formed hose (16281-65010), and stock hose would kink if you tried it. Less than $12 (but plus shipping) from an online dealer.
Scope, here are the pics: https://imgur.com/a/fzZmTlj

The red tinted buildup at the base of that tube coming from the intake looks to be indicative of the leak. Is that tube replaceable as well?
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Old 05-16-2019, 09:19 AM
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Looks like this is the part in question. https://www.yotashop.com/toyota-cool...n-90404-54036/
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Old 05-16-2019, 04:05 PM
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So, I ran another pressure test today, keeping a closer eye on that tube coming out of the intake (part is called a Union) and I was able to see coolant bubbling out of from the intake, not from the tube connection above. That being said, in order to fix this issue, is there any way to replace that part (or repair that connection) without tearing apart the engine?

In another thread, I saw Scope mention that trying to replace the Union itself is risky business because, if it's corroded, it can damage the threads on the intake body.

Anybody successfully replaced this part?
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Old 05-16-2019, 06:27 PM
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The best fix is to replace the intake gaskets if they are leaking. Might try to tighten the intake bolts a little bit, never works for me tho. Usually leaks worse. LOL I removed my union with a deep socket.
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