Cooling System Leak?

I just got done doing the 100k coolant flush and replace. I decided to get fancy-like with the OEM Tools Vacuum Re-filler tool.

I drained the coolant from the radiator and both sides of the block. Put the tool on the overflow tank and fired it up. Much to my disappointment, it wouldn't pull a full vacuum. After closing the appropriate valve, whatever pressure was in the truck's cooling system leaked out in about 30 seconds. This indicates a leak.

My first thought was that there must be an overflow hose somewhere pulling air. I searched everywhere to no avail. The only thing I could find was what appears to be a heater core drain hose in the firewall. I clamped it to no effect. Overflow tank only has the stubby nipple plug on the bottom.

I looked at all of the obvious places: radiator hoses, heater hoses, various bypasses. Listened for any hissing. Nothing.

Also, the coolant level was not low before I started. I have never seen any evidence of a coolant leak.

Luckily, I had an old spill-free funnel around. So job is done. But, i'm left a little puzzled.

Thoughts? Ideas? Harsh criticisms?

Edit: my truck has the 4.0

 

If you didn't have problems losing coolant before doing the service, I'd assume your system is pretty well sealed. Stock pressure for the radiator cap is something like 13 or 15 psi (can't recall from memory).

My guess would be to look at the tool itself and make sure things are sealing up. One guy on YouTube said his had leaks until he sealed it up with teflon tape/sealer on some of the threads. I don't have that specific tool but looks like it uses a tapered rubber cone into the overflow so that could leak too if you don't get a good seal. You could do some further testing on the tool itself if you have another spare container laying around your shop - something like an empty water/gas jug would probably work well if it doesn't have the crappy style vents.

If you got it done with the funnel I wouldn't sweat it. Funnels have worked for millions of people in the past and are stupid simple. Simple is sometimes better than fancy and this might be one of those times.

 

Thanks for your reply, @wi_taco. I'll have a look at the tool and check for leaks. I hadn't thought of that. And yeah, sometimes the low tech, tried-and-true method is better. Some things don't need to be fancy, I suppose.

 

Yeah, the way OP explained it.
He would have to pull a vacuum through through the radiator cap?
I don’t know, never done it the way he explained it.

I don’t like using a vacuum fill unless the vehicle is known for air locks.
Something about seeing all those hoses collapsed scares me.

 

The tool goes on the radiator neck. Cap off the expansion tank nipple with a vacuum cap

Don't feel bad. Gotta use it a few times to get the hang. You'll know your doing it right when radiator hoses collapse and squeeze down.

Keep trying, you'll get it

 

That’s how my kit works.
I’ve only used it once.
On a Ram w/ 5.7

I have never had an air lock issue yet with any Tacoma.
2.7, 3.4, or 4.0

 

Yep some engines don't trap air like others.the vacuum fill kits were practically invented for German cars with hoses going everywhere.

Japanese cars are usually easy to fill because the stat is usually somewhere down low, at the lower rad hose. Theres nothing in the way between the top of the engine and the top of the radiator, the air comes right out. American v8s like to put the stat at the top of the block. On those engines I'll either use a vacuum filler or pull a heater hose from the back of the engine to let the air out.

 

Worst I’ve had experience with was a 2.5L in a Nissan Altima.
That’s how I learned what a vacuum filler was? And why you needed one.

 

Sorry it took me a while to respond. No, I used the tool on the overflow tank. That's what the instructions described. It's also how it saw it being used in several YouTube vids.

The thought of using it on the radiator did cross my mind. I gave it a shot and found that the radiator neck inlet seemed too narrow to fit the tool. Maybe it could fit with some coaxing, but the overflow tank felt like the better host.

 

I got it to pull enough vacuum to collapse the hoses. That happened. But, once I removed the air, they would re-inflate after a few seconds. According to the instructions, re-inflation indicates a leak.

 

I think this is an accurate assessment, at least in my situation. After driving for about a week, I've had no pockets reveal themselves. The coolant level is steady and unchanged. No temp spikes.

I did a thorough job with the Lisle Spill-free funnel. The vacuum re-filler seems unnecessary and maybe ineffective (save for my own possible misuse) for the 1GR.

 

Were you shutting the valve on the tool? There's a valve on the tool/adapter that goes on the radiator and there's a valve on the suction hose that sucks in the fresh coolant. Also you have to get the adapter seal seated in the rad neck correctly, it takes some practice.

 

Sounds like the system is leak free, you'd have a drip somewhere by now if it wasn't.

The vacuum filler is a good tool. I'm only using it on maybe 1 out of every 15 cars.. but when you need it, you really need it

 

On the PreRunner turbo build that I did last year with a 1GR, I had to perform a coolant drain and fill. After topping it off, turned the heater on and let it idle. Watching the gauge, I noticed the temp starting to climb past 200. Shut it down and felt the hoses. Coolant wasn't circulating properly. I ended up pulling one of the small hoses by the thermostat manifold. Good thing that I kept my face clear because steam shot out with force! Once the coolant started coming out of the small metal tube, then the coolant started circulating proper at next fire-up. First time in all of my dealings on the 1GR, to ever have that issue.