Ls 400 Exhaust Flanges

39buss · July 2, 2012

No...not easy then!! I forgot to say earlier to disconnect the Battery before doing any electric welding on the car. Not appropiate now but best of luck with the repair.

ROYT · July 3, 2012

Having been through this I think the answer is to save up for new parts in anticipation of eventual failure. If you had time to experiment and had new pipe flanges made, these could be temporarily bolted to new cats. The Y pipe cleaned up and again temporarily refitted to get all the parts in alignment, tack welded in place, then removed to finish the welding completely.

A lot of work, even if you have a 4 post lift, which I don't!

ambermarine · July 5, 2012

Thank you ............ so at £1000 the car's going to be a scrapper at some time just because of the exhaust flanges !

Welding to rust isn't an option tho' .... so where does that take us ?

Difficult to comprehend it's just terminal .

Malc

The welding is across the stainless pipes of the cat and the Y pipe the rust as to be taken off ,this entails removing the studs and the rest of the flanges after a weld as been made in the exposed pipes so they stay in place while you remove the rest of the flange.If they have virtually corroded away that part is not to difficult.
It is a lash up and can only be rectified later by putting new cats and a Y section in at a cost of 12-15 hundred quid.

This as you say can terminate the vehicles life and I would suggest it as seen a lot off at the M O T.So those crafty engineers at Lexus did provide a suicide pill for the LS400 after all

Well it is done not pretty but effective,having looked at the rest of the exhaust system I would say I have two years at most before some serious decisions have to be made .I was quite shocked at how fast the system as detiorated over the last couple of years.

ROYT · July 5, 2012

I wonder whether the thin cat flanges could be built up with weld and then

ground/sanded/filed or whatever to make them flat again?

ambermarine · July 5, 2012

I wonder whether the thin cat flanges could be built up with weld and then

ground/sanded/filed or whatever to make them flat again?

My welder said he had great difficulty getting the weld to pick up on the cats he says the cat metal is different from the Y pipe metal and getting a bridge was near impossible he ended up webbing the area with solder wire so the weld would run accross the gap.

Personally as I said earlier having this £40 job done as given the car another couple of years, in that time something else going wrong could take away the decision of what to do then.

They are a great car but time does catch up with them and when they get over twenty years old the end seems to come very quickly just as it does in all of us at the end of our lives.I doubt that I would spend £2000 on a new exhaust system,which is what the car would require now this job as been done.

Malc · July 5, 2012

Hmmm .. but what on earth car could you get for £2000 of the same quality and longevity I wonder .. what a dreadful decision to have to make when the time comes.

Malc

ROYT · July 8, 2012

On eBay you can get a complete s/s system from the cats back

for £500. Quality unknown.

The cats are the killer cost if you want genuine.

ambermarine · July 9, 2012

Read an interesting article on Lextreme Forum yesterday on exhaust mods.

They have a guy who does water jet cut flanges for the ls400 out of mild steel for the manifold side of the cats for $30 from mild steel and for stainless $100.

The guy could obviously cut the flanges for the opposite end of the cat and the top of the Y pipe and if they were of stainless the problem of burnt and corroded flanges would dissapear.That would obviously entail removing the cats and the Y pipe for welding but might be worth it on a Late LS400 with lots more life in it than the early models.

ROYT · July 9, 2012

On mine the cat flanges fixed to the manifold had hardly any rust on at all.

The lower cat flanges connecting to the Y pipe were rusted away to less tha half the original thickness and worse in some places, as were the pipe flanges attached.

The USA fix would be well worth it even using mild steel again, mine did last 17 years!

Proves it could be done, alignment would be needed before final fix though,

flanges are angled.

Saving megabucks!

Malc · July 9, 2012

any suggested / authorititive conclusion yet then guys ? even just in summary for the less technically able amongst us please.

Malc

ROYT · July 9, 2012

Up to now the USA fix listed above, is about the only alternative to new parts all round.

Slow and no fun without a 4 post lift, but worth the saving, I did mine just with a decent pair of ramps.

Best with a helper, parts fairly heavy to maneuver on your own

The money saving will give you strength!

Redsteve · July 10, 2012

On Ebay you can get a complete s/s system from the cats back

for £500. Quality unknown.

The cats are the killer cost if you want genuine.

Hi Guys,

I know this is slightly off topic but I thought I would let you know my experience regarding the £500 eBay exhaust.

My exhaust was blowing at both flanges where the Cats meet the main part of the exhaust. I have always wanted the car to have a bit more of a growl so I thought I would see how much a new exhaust would be. I contacted 3 sellers on eBay, 2 of them never bothered to reply and the other quoted me £750.

I did a bit more research and found a company called Longlife Exhausts that offer a lifetime warranty and they have a branch quite close to where I live. I gave them a call and arranged to take the car in for them to have a look. After discussing what kind of exhaust I wanted (straightforward replacement or custom) we agreed on a price of £650 for a complete system from the Cats to the back of the car.

I decided on a custom cross flow pipe. It took the guys at Longlife almost 3 days to get the old pipes off and the new ones built and installed, most of the problems they had were with the manifold studs snapping off.

I am really happy with the work they did, it is top quality and they were really nice guys. In the end I paid them £700 because they had such trouble getting the old pipes off and what should have been a single day's work turned into almost 3.

I don't know if they would be able to get round the rusting flange problem, but I would be surprised if they couldn't, they really seemed to know their stuff.

Steve

abs66 · July 11, 2012

Nice. So what's she sound like?

Would you be able to do a recording or you tube video I would love to hear what those pipes sound like :-)

Redsteve · July 11, 2012

Nice. So what's she sound like?

Would you be able to do a recording or you tube video I would love to hear what those pipes sound like :-)

No problem Pete.

This video was taken with the engine stone cold so not a true representation of the sound but you will get the idea. It is a bit louder than I would have liked but, having said that, at 50MPH on cruise control you can barely hear the exhaust inside the car. It only really barks when you use some hoof.

Steve

"http://www.youtube.c...mVvuCryLI?rel=0"

abs66 · July 11, 2012

Thanks Steve, I suspect you had already had the youtube idea lol.

That is pretty loud but is like that because you floored it?

Redsteve · July 11, 2012

Yes, I was using a bit of throttle. Normally, when the car is warmed up, it is a much more subtle sound. The fact it is a crossflow pipe gives it the uneven burble at about 1200 RPM.

It can be quite funny watching people do a doubletake when the car goes past them, you can see them thinking that the car doesn't match the noise.

The added benefit is that, because the pipes are much less restrictive, the performance of the car is improved. I also get about 3MPG more now than I did before.

Steve.

abs66 · July 11, 2012

That's interesting, I'm obviously a bit thick with regards exhaust systems as I didn't realise you would get better mpg and that the sound changes when warmed up.

You live and learn.

Thanks for the feedback Steve, very useful info.

Pete.

bookend · July 11, 2012

That sounds sweet

abs66 · July 11, 2012

So what's the next video Steve? A ride along at normal throttle with windows open to get some sound in ;-)

Go on, you know you want to lol.

runsgrateasanut · June 16, 2015

Read an interesting article on Lextreme Forum yesterday on exhaust mods.

They have a guy who does water jet cut flanges for the ls400 out of mild steel for the manifold side of the cats for $30 from mild steel and for stainless $100.

The guy could obviously cut the flanges for the opposite end of the cat and the top of the Y pipe and if they were of stainless the problem of burnt and corroded flanges would dissapear.That would obviously entail removing the cats and the Y pipe for welding but might be worth it on a Late LS400 with lots more life in it than the early models.

Reading this old article and in conjunction to a thread I've already posted today, I contacted a guy in UK who sells the upper Flanges to see if he could make lower flanges. The Cats have a 54mm external diameter 7mm length good pipe protruding where the gasket fits over. If I could find a piece of 54.5mm S/S pipe about 10-15 mm?? length pre-flanged (no bolt holes) to weld onto the Y pipe after the remains of that flange is removed it may be a permanent fix. So welded both ends.

Not totally simple, as the y pipe has a strengthening spine and length of part difficult to be sure of. He is giving the problem some thought. Don't hold your breath.