TyneeGX

Anyone ever have a coolant leak at the front water bypass joint? There is an O-ring there that I think has failed. There are also lower gaskets on the bottom of the bypass joint, the left one has pooled coolant around it, but this may just be leaking from the O-ring above. The O-ring seals the slip joint connected to the water inlet housing. See diagram and photos.

So...:
1. Has anyone had a similar problem?
2. Is the O-ring a common failure part, or if I am getting into this, should I look at doing the lower gaskets too?
3. Is this repair fairly straightforward, or a PIA?
4. Should I attempt myself, or give to a shop?
5. If I attempt myself, what parts and supplies should I have on hand for the procedure?

Symptoms:
The truck heater was only functioning at high RPMs. I added coolant, over a gallon, burped the system, and topped off the reservoir (which was dry). Now, I've found the leak, but when the coolant is topped off, and the engine gets up to hot, the overflow tank fills over capacity and starts to drain out the drain tube on the top. Not sure if this is an indication of bypass joint failure or not?
Thanks for any help:

6080prado

I had to replace my O-ring. It was tough to find since the coolant would pool on the intake and burn off. It can get nicked pretty easily when doing the timing belt or water pump. I assume that's how mine got done as it had the timing belt done by the PO about 10K earlier. It is easy to replace: two bolts hold the inlet and you don't lose much coolant in the process.

Yours is clearly leaking and should be replaced. However, it should only cause loss of coolant, not the other symptoms you describe.

As to your other symptoms, I guess I am not fully understanding your description. You said you "topped off" your reservoir. You should only fill it to the lower line when the engine is cool. This is because it will expand when the engine heats up. So if you truly topped if off, I'm not surprised it overflows when it gets hot. That would be normal. If you had it at the lower line and it is overflowing, that is an issue.

So if it overflows after being filled to the lower line, two things come to mind:
A bad radiator cap. A proper functioning radiator cap will send fluid out when hot and suck it back in when cool. But when they go bad, they sometimes don't allow fluid back in. So it keeps letting fluid out when hot but never sucks it back in. Eventually overflowing the reservoir. This would take a couple heat cycles.

The other thing, gulp, could be a bad headgasket. If your truck overheated, the head could have warped and now it is sending hot combustion gasses into the coolant. this hot, pressurized coolant gets past the cap and overflows your reservoir.

Let's hope I'm just misunderstanding your post or it is just the cap. Hopefully not a headgasket.

FrankT

Oh heck yea, replace that O ring and reseal the water inlet housing with your favorite flavor of RTV...
You should be good after that.
No need to dig any further.

Drain at least 1/2 of the radiator and disconnect the radiator hose.
2 bolts hold the water inlet housing along with the RTV that acts like glue, so some gentle prying might be needed.
Clean off all the old RTV from both surfaces and reassemble with a new O ring and RTV.
There is a short hose that is easier to disconnect and connect with the water inlet housing off then you can bolt the housing on.

Good luck...


Cool light BTW

TyneeGX

Awesome, thank you both.
I agree, I think it's just the o-ring. I'll replace that and see where that leads me, I appreciate the quick response and personal experience.
As far as I know, the engine hasn't overheated. I also did fill to the "full" line, so hopefully that explains the overflow. The oil and coolant both look clean, so I'm hoping no seals have been compromised. Pretty sure the water pump, etc. was recently replaced just before I purchased, so that may explain the failed o-ring.

So the last piece is the O-ring part number, anybody have that?
Thanks all!

TyneeGX

Thanks about the light, another amazon find. Funny thing is, look at one of the pics, the engine cover nut is attached to one of the light magnets. Almost lost that sucker...

FrankT

O- ring part number 96761-35035
aftermarket Part Number: C31699

TyneeGX

Stellar, cheers!

mswtoyota

Last time my Supra did that, it was the head gasket.

TyneeGX

Thanks everyone for the input and help. Replacement complete. So far so good. When I popped off the water inlet housing, it easily slid off the block. The rtv gasket was crumbling and failed. The o-ring was flattened, and when removed, it was brittle and cracked in half. So I'm pretty positive this was the only problem. It looks like this housing may have been removed for service, and the o-ring and rtv not replaced but reused. The procedure was pretty simple. I drove around for 2 days, and there is no moisture on the block or coolant dripping below. Fingers crossed.
Next week: transmission fluid and filter change.

TyneeGX

Help! Apparently my celebration was premature. There is no longer any leakage at that slip joint, it's all dry and clear, but coolant continues to slowly drip down the engine block and drip off the lower frame cross member and front of the transmission.
Has anyone had a leak elsewhere? Somewhere underneath the intake manifold? I can't see a leak, but there is moisture on top of the block, just behind that bypass joint tube...

neub

Dealing with the same issue, so I hear your pain. I've narrowed down to the o ring at the water pump outlet. The said o ring sits between the water pump outlet and the heater pipe (not hose - it's metal). Now that was the possible good news.

There are two ways to get to this o ring:
1. Remove radiator, fan, thermostat housing, timing belt cover, accessory belt, detention the timing belt, remove the belt - replace o ring. Then repeat in reverse order.
2. Remove the plenum, disconnect fuel lines, disconnect throttle cable, disconnect plugs, fuel pulsator....remove intake manifold, then you see the pipe.

Still haven't decided if it's time for an early timing belt or new intake manifold gaskets....

TyneeGX

Egads, Batman!
I was afraid of that. Ok, well the next questions I guess would be:
1. Is this something a weekend mechanic could handle without seriously damaging the engine?
2. Which procedure is easier?

I just did the brake discs and pads, transmission pan drop and fluid flush/refill, and then this last coolant fix. I guess I saved enough to warrant having a garage do this last procedure for me, but I always hate letting someone touch my stuff. Volkswagen dealers have caused $5,000 in damage to my other car, and tried to blame me. Trying to avoid that fiasco ever again... And I did do an intake manifold gasket replacement on a GM minivan before, with success, so I feel a little better about going in from the top. Plus the GX seems to have a lot more space than a transverse-mounted mommy-mobile engine bay.

Have the "IH8MUD" guys done this before? They seem to have experience with the 4.7L.

Please keep me posted on what you find out. Thanks!

neub

This is a pretty useless forum as it seems. Ill be going the new timing belt water pump route.

If your tb/wp are fairly new I'd suggest removing the intake manifold. DIY or pay a shop 4 hours labor. Good luck

neub

[QUOTE=TyneeGX;9365869]Anyone ever have a coolant leak at the front water bypass joint? There is an O-ring there that I think has failed. There are also lower gaskets on the bottom of the bypass joint, the left one has pooled coolant around it, but this may just be leaking from the O-ring above. The O-ring seals the slip joint connected to the water inlet housing. See diagram and photos.

So...:
1. Has anyone had a similar problem?
2. Is the O-ring a common failure part, or if I am getting into this, should I look at doing the lower gaskets too?
3. Is this repair fairly straightforward, or a PIA?
4. Should I attempt myself, or give to a shop?
5. If I attempt myself, what parts and supplies should I have on hand for the procedure?

Symptoms:
The truck heater was only functioning at high RPMs. I added coolant, over a gallon, burped the system, and topped off the reservoir (which was dry). Now, I've found the leak, but when the coolant is topped off, and the engine gets up to hot, the overflow tank fills over capacity and starts to drain out the drain tube on the top. Not sure if this is an indication of bypass joint failure or not?
Thanks for any help:











[/QUOTE

Also if your radiator is original. It's likely leaking, in fact my old leaking radiator passed a pressure test without issues.

Remove the shroud and look down left or right hand sides. Coolant is soft so it leaves brine stains.

TyneeGX

[QUOTE=neub;9401500]Naw, radiator is clean. All the under shields are removed, and the fluid is leaking down the backsides of the engine block and transmission, nowhere near the front radiator.