GX470 Coolant leak - head or ? (1 Viewer)

[bgampe]

2003 GX470 with 150k miles. Pump and belts done by PO at ~120k, and I just replace the thermostat inlet housing o-ring which I though was causing the leak due to visible seepage.

After filling the reservoir to the full line, the next day it's back to half full. Coolant is visible on the front passenger side of the engine where the head mates to the block. I removed the PS bracket and the belt cover but can't really tell if the leak originates further up. I can also see wetness on the block under the manifold on the same side so assume it's related.

This has been going on for a while but the leak is getting more prominent. Any thoughts on the source? Hoping it's the water pump and not a head gasket.

Don't know if the engine ever overheated but it runs great and temp is always at mid-point on the temp gauge.

 

[z00t3ch]

There are two small coolant lines that go through the throttle body and back toward the passenger valve cover. Have a look at those, the hoses are rubber and the fittings plastic so perhaps you have some age-related dry rot or whatnot.

 

[Tanaman]

I would also check the coolant line that runs into the back of the thermostat housing. Mine had an O-ring that was crushed due to poor installation and was leaking.

 

[bgampe]

There are two small coolant lines that go through the throttle body and back toward the passenger valve cover. Have a look at those, the hoses are rubber and the fittings plastic so perhaps you have some age-related dry rot or whatnot.

I see two water bypass hoses going into the throttle body from the passenger side - those are dry. I don't see where they come out.

I would also check the coolant line that runs into the back of the thermostat housing. Mine had an O-ring that was crushed due to poor installation and was leaking.

The coolant line into the thermostat housing appears to be metal and I don't see any sort of clamp/connection. It's also clean. The only place I saw pink dry coolant was around the inlet pipe o-ring which I replaced and resealed the unit.

I placed a balloon over the radiator fill hole and started the engine cold - the balloon didn't fill up and I didn't see any bubbles in the reservoir. I'll rent a combustion leak detector / block tester tomorrow and try that next.

Visually, I don't see any leaking hoses, but also see a wet trail down the center of the oil pan and up in the plastic belt cover (weep hole?) when looking up at the crank pulley from underneath. That may be water from yesterday's work, or it could be the source of the leak, which seems odd if the WP only has 30k mi on it. if it's the WP, does it make sense that coolant is running along the head gasket and down the block behind the PS bracket, but the Driver's side of the block in dry?

 

[z00t3ch]

I see two water bypass hoses going into the throttle body from the passenger side - those are dry. I don't see where they come out.

One in, one out...

 

[bgampe]

I had the system pressure tested the other day and no leaks according to the shop I took it to. They had it pressurized for 30 min. Visually all leaks were dry, but again this morning there's coolant running down the side of the block and the vin area under the throttle body looks partially wet. Since I don't see leaking from the two water bypass hoses, and I just replace the thermostat housing inlet o-ring and resealed the port mating surface (no visible leaks there), it's possible the leak is coming from the back of the water pump inlet o-ring.

Any suggestions on how to confirm this is the leak?

 

[IwantPrado]

I had the system pressure tested the other day and no leaks according to the shop I took it to. They had it pressurized for 30 min. Visually all leaks were dry, but again this morning there's coolant running down the side of the block and the vin area under the throttle body looks partially wet. Since I don't see leaking from the two water bypass hoses, and I just replace the thermostat housing inlet o-ring and resealed the port mating surface (no visible leaks there), it's possible the leak is coming from the back of the water pump inlet o-ring.

Any suggestions on how to confirm this is the leak?

View attachment 2182789

View attachment 2182805

Any luck finding the source of the leak?

 

[bgampe]

Any luck finding the source of the leak?

As far as I can tell it's the other o-ring behind the water pump. Oddly, it only leaks when the coolant level is above a certain point in the reservoir (somewhere btw low and full). I suspect that's because leak is at that point, so when it's lower it doesn't leak. In any case, it's not overheating and the level isn't dropping so I'm not fixing it till it's time for new belts/pump.

 

[IwantPrado]

As far as I can tell it's the other o-ring behind the water pump. Oddly, it only leaks when the coolant level is above a certain point in the reservoir (somewhere btw low and full). I suspect that's because leak is at that point, so when it's lower it doesn't leak. In any case, it's not overheating and the level isn't dropping so I'm not fixing it till it's time for new belts/pump.

Thats good to know!
I just noticed a couple of quarter sized pink spots on the driveway floor. Its right in the middle between and behind the front axles. The car has been sitting for a couple of weeks. Weird. I'll have to investigate mine... I'm like you, had TB, WP and radiator service within 15k miles. Maybe old hose/connector leak.
Thanks for response!

 

[subspd]

I have a crazy slow leak somewhere too. It takes about a year to drop from full to minimum. Nothing is visible. WP and TB and Radiator are all less than 2 years old. I kind of just don't worry about it right now. It is so slow. But I suppose I need to get it pressure tested and try to find it...

 

[IwantPrado]

I found my leak: driver side intake manifold gasket is leaking towards the back. Gathering all the parts for the gasket replacement job. Thinking about SAIS bypass and starter replacement while I’m there.

 

[GX460fan]

I just completed TB and WP service at 177329 miles. I was really not happy to do it since there were no indication it had EVER been done. The belt I took off looked great and I felt even more uneasy to pull apart a perfectly functional engine but I figured I was nearly done with disassembly. Turns out the water pump was failing and I didn’t even know. Fast forward and now I have a serious leak. Not the o ring at the top and it looks like from behind the tb covers. Guess who gets to do the job again...The tb/ wp on my kids 1999 Toyota Camry 4cyl wasn’t this much of a pain...

 

[IwantPrado]

I just completed TB and WP service at 177329 miles. I was really not happy to do it since there were no indication it had EVER been done. The belt I took off looked great and I felt even more uneasy to pull apart a perfectly functional engine but I figured I was nearly done with disassembly. Turns out the water pump was failing and I didn’t even know. Fast forward and now I have a serious leak. Not the o ring at the top and it looks like from behind the tb covers. Guess who gets to do the job again...The tb/ wp on my kids 1999 Toyota Camry 4cyl wasn’t this much of a pain...

How did it go?
I did my intake manifold gasket and recorded my experience here:



But 2 months later I smell the coolant again, and, although the coolant tank is nearly full, I saw the first drop of coolant on the garage floor again after the truck sat for a week. Scratching my head...