Rear Water Bypass Leak

[MARK LOVECCHIO]

Ive got a leak coming from the rear coolant bypass where the metal tube goes into it. shouldnt there be come sort of clip or gasket on this tube? I can wiggle it out pretty easily. Does anyone have any diagrams or pitures or experiance with this?

thanks

f.y.i. this is on a vvti 4.0 its actually a gs400, but same engine on the LS400

[92Lex]

There should be a clamp of some sort on all rubber coolant hoses. If it's a metal tube going into another piece of metal/plastic, then there should be a gasket/o-ring on that tube.

[MARK LOVECCHIO]

Ill have to check for one. I suspect the tube might be bent too from me prying around back there. If not, would coating the outside of the tube in RTV or something similar then sliding it in the hole work to seal it? could this cause cooling system problems at all? If it makes any difference, coolant flows out of the hold up the tube and into the heater.

[92Lex]

I wouldn't trust depending on silicone to stop a leak in a pressurized system. I suggest adding a clamp to that hose.

[mehullica]

The metal tube is pressed into the water bypass and sealed from the factory. I would replace the bypass.

[MARK LOVECCHIO]

well mine surely doesnt look pressed or machined by any means. it just slips into the hole, and if I wiggle it hard enough for 5 minutes or so it slips (wiggles) out. there is no place for a clamp and I dont think there is any o-ring either. the last thing I want to do is take apart the whole top of the engine for a tiny drip leak.

[LScott400]

well mine surely doesnt look pressed or machined by any means. it just slips into the hole, and if I wiggle it hard enough for 5 minutes or so it slips (wiggles) out. there is no place for a clamp and I dont think there is any o-ring either. the last thing I want to do is take apart the whole top of the engine for a tiny drip leak.

I would think you could reseal the pipe to the bypass. The question is can you get the mating surfaces clean and dry in preparation for the sealer without removing the bypass assembly.

[mehullica]

If the fit is loose enough to "wiggle" the tube out, you should replace the bypass assembly. Even if you could "seal" it somehow, what are the chances that it won't blowout on you on a hot day as you're driving down the road? You'll overheat and be stranded somewhere. That tube and heater hose will flex as the engine loads up and will always have some tension on it. The bypass isn't too difficult to remove once the intake manifold is off.

[92Lex]

Removing the intake manifold isn't something you can do in an hour.

[mehullica]

Sure, if you've never taken one off, it'll take some time. I've been working for a dealer for many years now and to me the job is easy. A newbie should be able to do the whole job in less than 3 hours.

[92Lex]

Book calls for 8 hours. I'd be surprised if a newbie were able to do it in 8 hours. I can replace Honda timing belts in under 1 1/2 hours and still can't replace starters in these cars in under that time.

[mehullica]

Warranty flat rate is 1.8 hours. Much easiler than a starter R&R. Of course skill level and quality of tools have a big role in the time it takes to do the job.

[92Lex]

Are you talking about the intake manifold or air intake assembly?

[mehullica]

Intake manifold.

[92Lex]

R&R of the intake manifold isn't 1.8 hours. I've used Mitchell Management Plus and All-data. If you do intake manifolds on these cars every single day and were extremely talented, then there is a slight chance that it's possible.

[mehullica]

I meant, The Lexus warranty flat rate is 1.8. What Lexus pays the dealer for a warranty R&R. My dealer has 8 techs and all of us can replace a starter is a GS400 or Ls400 in under 2 hours. Talents not really as important as having done the job hundreds of times.

[MARK LOVECCHIO]

very true, when i removed my intake to repair the knock sensor wire, it took almost 3 hours, between me spending an hour & a half looking for solder and tools & trying to figure out how to undo those black clips on the wiring harness. That was the first time id seem the lexus engine underneath the engine cover. I could probably do it in 30-45 minutes now.

Fixing the leak didnt involve removing anything; I just put blue RTV on the tube. BAM!

[firstgenLSowner]

Ive got a leak coming from the rear coolant bypass where the metal tube goes into it. shouldnt there be come sort of clip or gasket on this tube? I can wiggle it out pretty easily. Does anyone have any diagrams or pitures or experiance with this?

thanks

f.y.i. this is on a vvti 4.0 its actually a gs400, but same engine on the LS400

I don't know if were talking the same leak but I had a coolant leak near the access panel to the flywheel near the rear main seal and it appeared to be coming from the the water bypass tube interfacing with the water pump. I just changed the water pump and suspect the o-ring was misaligned or was the wrong size. Is this the leak your talking about? Do you know if there is a way to change the o-ring without removing the pump, such as access from the top (remove intake manifold and pull the tube out of the pump? Either way it looks like it's going to be a real pain to get to!!!