Hello, I own a toyota truck v6 4x4 1991, recently I'be been chasing some coolant leaks and ended up replacing a couple of hoses on the back of the engine (u-hose was damaged) and some of the heating hoses also leaked but a little bit, I just replaced them. Afther that, I drove the truck for a couple of days and couldn't find no leaks at all when the engine was on. I just leave it there for 3 days on the garage and today I noticed a pond of coolant under the truck. I check the hoses and everything looked normal but I noticed that it was coming from the front of the engine, and I found that the leak started on the end of the metal part that connects the hose that goes from the TB to the intake manifold, I googled it and apparently its called the Manifold Union No.1. It looks like it is leaking from the internal screw thread, the hose above has no coolant traces at all. Can someone tell me about why is that part leaking only when the engine is off? Can I just simple replace it just unscrewing it and putting the new one, or just tighten it a little bit? Below there is a picture for your reference pointing where the leak comes from. Thanks in advance.

Manifold Union No.1

 

Difficult to see if just tightening the manifold screw nearby would help. If the leak is happening on the male end of the hose connection, looks like there's some adhesive strip covering...maybe something similar or some thread sealant tape can help. Seems like that part developed a crack from the stress of thermal expansion and contraction, which in your case appears to happen during contraction, as the engine cools.

I'd stay away from rad/cooling sys liquid sealers. Rather fix it the right way than potentially make a problem worse.

 

How long have you owned the truck??

By Pond of Coolant it seems as soon as the coolant is above this fitting it just pours out till the level drops below .

As fast as it gets poured in it pours out .

Not knowing where you live or the miles on that engine.

Your saying this fitting is leaking where it threads into the manifold .

Brass fitting going into Aluminum .

It might be leaking because it is already cracked .

I venture cracked above the threads unless this fitting was removed and never installed correct

I would suggest a coolant system pressure tester to pin point your problem to make sure

 

Hello,

Did you ever find a solution to this leak? I have the same leak right now and have just been filling it as it slowly looses coolant. Any suggestions on how to repair?

Thanks,
David

 

Hi, after checking all hoses I ended up removing the lower intake manifold and the gasket was really bad, that was the source of the leak. There was a pond of coolant below de upper intake manifold too. No leaks after replacing that gasket. Hope it helps.