Hey all! Round two of replacing the gasket between the manifold and down pipe (Y pipe). I did it last week and still had a leak from there. Decided to try again with OEM gaskets. Last week, I had the connection between the Y pipe and resonator loose, should I do that again? The surfaces are flat and clean, so not sure how the leak can persist, yet it did. Seems straightforward and super simple, but for some reason I'm having trouble.

 

I would loosen the Y pipe outlet and try again. That style connection allows for some alignment so it could be holding the Y pipe at a funny angle.

 

I'm having the same issue, at first there was no leak after a new gasket. But every two days or so when the engine was cool, I would re-torque the nuts. It took about 4 re-torque events before the nuts stopped turning, and now the leak is back. I'm going to try and stack two OEM gaskets (used aftermarket the first time) and see how that works out. Currently there is no sealant that I know of that can handle the heat right there, I've measured upwards of 600f at that joint, so that rules out copper RTV. Hoping to get that done next week, fingers crossed!

Rhys L.

 

Back in the day when I had MG's and Triumphs, there was something called "exhaust putty"... let's see if I can find it... yes, Permatex makes some called "80335 Muffler and Tailpipe Sealer." There are other brands too. The stuff cures with heat and is more like concrete or mortar, but when it's wet it actually makes it easier to slide pipes into proper alignment. It seals gaps between manifolds and downpipes, and between sliding pipe sections that telescope into one another and then use U-bolts for clamping.

I had the same problem when my Y-pipe on RRC blew a hole in it and I needed to get it welded up. It was easiest to disconnect the rear pipe from the Y-pipe, and then lightly connect the two downpipes on the Y-pipe to the headers before lightly reconnecting the rear pipe. I remember needing to buy three new forcing rings or whatever you call those thingies... my originals were rusted and had pits in them that prevented tight sealing. I also needed to take a wire brush to the mating surfaces on the Y-pipe's downtubes because they were slightly pitted too. OK, that's all out of order, but you can figure it out.

The caveat about the exhaust putty is that when you take it apart, it sticks to steel just as strongly as concrete, and I used a hammer and chisel to clean it off of an old Spitfire's pipes after I overhauled its engine.

Good luck,
Scott

 

Loosen the joint downstream and then tighten the y-pipe. Then retighten the joint

 

Follow-up, this is the reason why it kept leaking despite new gaskets. https://landroverforums.com/forum/di...t-leak-102344/

 

I have the same problem - it is still leaking after new gaskets and several re-torque attempts. To me it looks like the Y-pipe measurements are off, so it can never seal properly on both ends. I will try it again with a beads of Permatex 81878. Some people suggested that here and in other forums.

 

I’d advise against fluid applied gaskets. Something else is wrong, and it’s quite likely there are cracks at the flange. I missed seeing mine twice. They’re sneaky. Ha

 

With soapy water applied to the connection and pressurized air into the end pipe it bubbles like crazy at the gaskets, but nowhere else. My leak is not severe, if noticeable at all, it just gets exposed when doing a pressure test. When I installed new gaskets I cleaned and inspected the flanges and they looked fine. I believe it is more likely that the Y-pipe deforms over time due to the heat cycles. As soon as the bolts between the manifold and the Y-pipe get lose a little bit (mine were quite lose) the pipe won't be kept in its original shape.

Maybe one could heat up the pipe with a torch so it becomes soft and the connection can be torqued so it finally seals.

 

I had tiny leaks there that went away when it warmed up, finally tightened the nuts on a cold morning and that solved the problem. I had leaks everywhere after having a new Y pipe installed. Fix one and the next would appear. Lol. First the downpipes, then the joint in the one side of the Y, then the flange at the cat back.