Ls 400 Exhaust Flanges

ROYT · June 20, 2012

One of my exhaust flanges is leaking, and the others are shot.

Presumably the flanges are put on before the ends of the pipe are flared.

Mine are rusted away and need replacing, has anyone overcome this problem, no flanges are listed as spares, plus how would you get them on the pipe past the flared end?

Why a stainless exhaust with plain steel flanges?

The thoughts of replacing the whole system is making my hair fall out.

moriwaki · June 20, 2012

I had exact same dilemma....you have no choice but to replace the cats and centre H section it is connected to.....unless you can find a master fabricator willing to take on the job....but it would be hardly worth their while when I asked around.....I bit the bullet and went to Lexus for the parts and fitted them on a friends lift.....

But I too questioned the daft idea of mld steel flanges onto stainless system...

....get yourself some replacement manifold to Cat studs too....they will need burning gear to get them off if they were anything like mine...plus new nuts and gaskets.....not too expensive off Lexus....

But it is worth it to keep the Best Car in the World in fine fettle ....No ?

steve2006 · June 20, 2012

I've seen complete custom built stainless steel systems on fleabay for around 350.00 made and fitted while you wait, probably cheaper than getting the OEM parts?

ROYT · June 21, 2012

Thanks guys, looks like a severe pain in the wallet is pending.....

Malc · June 21, 2012

Hang on a minute .......... I remember reading, maybe years ago of this sort of problem arising and maybe, just maybe there was a simpler solution !

I can't remember and I'm not at all sure where to look BUT there was something that was said to help on the wallet !

Does anyone have a longer memory than me I wonder.

I'm saying this because my Lexus just had an emissions advisory on the MOT and my mechanic guy looked and used some gunge to temporarily fix the imperceptible leak . He said it will be fixable like this for ages BUT I would like to remedy somehow and very cost effectively.

So can anyone help on here as to what the simpler and more cost effective solution might be for the future please ?

Thanks.

Malc

sir john · June 21, 2012

I have had the same problem for the 3 1/2 years i have owned my 93 LS. You can use all sorts of gum to do a temporary fix (pastic metal works best) but its only temporary.

I have found a fabricator who is going to weld my cats to the Y pipe as a final fix for about £80.

It should last for another 5-10 years which will suit me.

Any good fabricator should be able to do this. My guy is a builder of trailers and fitter of tow bars so a good welder and he has a 4 post lift.

ROYT · June 21, 2012

I might go down the welding route as a last resort, Or even bite the bullet and replace them.

Meanwhile I'm trying to invent a clamp [like you do] in two halves that bolts together when fitted, before you fit the normal clamp bolts..

How sad is that?

Malc · June 21, 2012

That sounds a promising and cost effective solution then.

Do let us know how you progreess with it.

Thanks.

Malc

ROYT · June 22, 2012

Check out Corsica exhaust clamp repair on Youtube, comments please, are these the answer?

ambermarine · June 23, 2012

If you have rusty clamps etc. [like me].

Checkout Youtube, 'Corsica exhaust clamp repair', is this what we need?

.How laid back is this guy!

I would expect any good fab shop could make those up ,unlikely to be able to purchase from anywhere as a shop packaged item in this country but I will check out the auto stores in the states on my Fl trip next winter.Having now inspected mine the drivers side as corroded to the extent that the steel make up of the cat and the exhaust pipe are showing this makes it easier to fill in with brazing and should the bolts which are really bad fail, the pipe and cat will stay together if the brazing is done properly.The issue over the clamp repair is a bit complicated by the oygen sensor furniture on the exhaust pipe and at first glance looks like it would impede the placing of the repair flange.Also problematic is the size of the clamp ,Autozone in the states only displays one size on their website , will it fit on the LS400, I doubt it.The other issue concerning brazing together the cat and pipe, should the cat fail it will be the end of my car as I would not go to the trouble of having everything cut up to put in a new cat.

DrKevan · June 28, 2012

Unsure if is the same, but Roy's Motor Company in Norwich mentioned something similar when they patched my y-pipe. A previous LS they'd fixed needed new cats, but the exhaust flanges where gone. My impression is that they achieved a mend by removing flanges from scrap exhaust and welded them on as replacements.

sir john · June 29, 2012

My fabricator chappie cut out a leaking flexi section and welder a new flexi section (new from exhaustpartsuk) without removing the exhaust from my Rover 75.

£40.

I was well impress. As soon as the ground in front of the garage dries out enough for me to get the LS out of the garage he will be cutting and shutting the flanges on that for £80.

ROYT · June 29, 2012

Hope it all goes OK for you, when I removed the pipe and cats the flanges had rusted away to paper thin and to avoid a long drawn out job I gave in and bought a new Lexus Y pipe [it includes the centre box] and new after market cats. New Lexus Y pipepipe £208 +vat, this was with a 25% discount as they had an offer on exhaust parts!. Sounds a lot, but it is a sustantial item in s/steel. Not so good were the cats @ £440 each plus vat so I went aftermarket at about half price. Gaskets and hardware about £50 As the car is a '94 model I suppose you could say it's all you can expect, the sad thing is none of it would have been needed if the flanges had been stainless in the first place. Those prices are doing the job myself....not a lot fun....the most risky part was the risk of breaking the top cat/manifold stud, as this would have been an absolute nightmare to get at to replace. If anyone wants to try the split flange replacement idea, Google www.exhaustdirect.ca. I think there is a branch in London, looks like they might work if the flanges are not too thin.

I just added to this post that the Y pipe could probably be saved by removing the remains of the flanges and welding new flanges on if you know someone to make them. [waterjet cutter?].

If anyone wants to try they can have the pipe free of charge [collect it!].

[the rest of the pipe and stainless box are OK]

Let me know asap before I bin it!

ambermarine · July 1, 2012

Hope it all goes OK for you, when I removed the pipe and cats the flanges had rusted away to paper thin and to avoid a long drawn out job I gave in and bought a new Lexus Y pipe [it includes the centre box] and new after market cats. New Lexus Y pipepipe £208 +vat, this was with a 25% discount as they had an offer on exhaust parts!. Sounds a lot, but it is a sustantial item in s/steel. Not so good were the cats @ £440 each plus vat so I went aftermarket at about half price. Gaskets and hardware about £50 As the car is a '94 model I suppose you could say it's all you can expect, the sad thing is none of it would have been needed if the flanges had been stainless in the first place. Those prices are doing the job myself....not a lot fun....the most risky part was the risk of breaking the top cat/manifold stud, as this would have been an absolute nightmare to get at to replace. If anyone wants to try the split flange replacement idea, Google www.exhaustdirect.ca. I think there is a branch in London, looks like they might work if the flanges are not too thin.

I just added to this post that the Y pipe could probably be saved by removing the remains of the flanges and welding new flanges on if you know someone to make them. [waterjet cutter?].

If anyone wants to try they can have the pipe free of charge [collect it!].

[the rest of the pipe and stainless box are OK]

Let me know asap before I bin it!

Hi

Having read the previous post I was interested to see the canadian company who were mentioned,having viewed their website and checked out the split flange arrangements the biggest inside diameter they do is 2 and 9/16th inches.with this information I crawled underneath My Ls400 and checked out the pipe dia .the cat side is the problem it is at least 2and 3/4 inches but not only that the oxygen sensor protector which originaly was fastened with the flange stud is in the way.

To use the split flange would entail removing all of the old flanges on both the cat and the box pipe .This operation would be difficult to do without removing the box pipe which in turn would require other well rusted flanges being disturbed further back.After some careful consideration of the excellent posts on this subject,the alternative of welding the cat and box pipes seems to be the best way to go both in reducing expense and aggro.I believe the 1200 pounds spent is a matter of personal choice ,the trouble with owning one of these cars is that we think they will run forever and non more so than myself.

But realistcally the welding if done properly will last as long as anything else on the car and because I don't need it to last longer then I will choose that route.

ROYT · July 1, 2012

Agreed, Having new flanges made for the pipe is probably feasible, the centre flange only had rusty bolts and was no problem.

As you say the cat flanges are the problem due to the diameter and aftermarket split type flanges didn't look beefy enough for the job anyway.

Welding will hopefully postpone the expense if anyone prefers that route and will

maximize the lifetime of the cats as the rusty flanges made my good cats scrap.

As an excercise it would be interesting to know the cost of having new s/s flanges

made for the pipe.

A waterjet cutter should fly through the job. [i kept a template of the flange size if

anyone fancies trying!!]

Malc · July 2, 2012

Can we just have a rain - check with this please.

Have we reached any sort of conclusion guys ?

Am I reading that if the flanges are kaput or starting to go that way, that if they are remedied somehow BEFORE they get too bad then that will preserve the life of the cats ? and that if they are left to go too far in deteriorating then that will accelerate the death of the cats, where they too are affected by tin mice.

Just some informed view and guidance please from someone who has the knowledge please.

I'm confused ...... but that's not difficult !

Thanks

Malc

ROYT · July 2, 2012

Easy!, if you let the flanges rust away, you will have to weld them or buy new cats and Y pipe.

Cost more than a grand if you use genuine cats.

ambermarine · July 2, 2012

Can we just have a rain - check with this please.

Have we reached any sort of conclusion guys ?

Am I reading that if the flanges are kaput or starting to go that way, that if they are remedied somehow BEFORE they get too bad then that will preserve the life of the cats ? and that if they are left to go too far in deteriorating then that will accelerate the death of the cats, where they too are affected by tin mice.

Just some informed view and guidance please from someone who has the knowledge please.

I'm confused ...... but that's not difficult !

Thanks

Malc

Very droll Malc,The issue is with the mild steel flanges corroding with time and atmospheric conditions,The pre-empt remedy is out of the question because any anti corrosive treatment would just burn off .The point regarding the cats is that the mild steel flange corrodes away to nothing ,destroying the fastening aspect to the next component of the Exhaust system.

The various fixes alluded to in the previous posts are split into, tried that does'nt work, done that it does but it is expensive,that works but it is a lash up and that might work but I doubt it.

does that make it any clearer Malc.

Malc · July 2, 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

ambermarine · July 2, 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

Malc · July 2, 2012

Bugger ............ and there's me thinking my LS400 would see me out for the rest of my driving days ...... . about another 25 years in my reckoning.......... and that would make the car 42 years old ........... my classic Triumph is 80 this year so maybe..... just maybe

Malc

ROYT · July 2, 2012

Just to drag this out a bit further, you could probably rescue the Y pipe by

having new flanges made and welded onto the stainless pipe.Reducing a £300+

bill.

The cats are the main problem and even after market are not cheap.

Scrapping the car depends on what the rest of it's like.

Minor dings on mine but only done 74,000 odd miles....

ambermarine · July 2, 2012

Just to drag this out a bit further, you could probably rescue the Y pipe by

having new flanges made and welded onto the stainless pipe.Reducing a £300+

bill.

The cats are the main problem and even after market are not cheap.

Scrapping the car depends on what the rest of it's like.

Minor dings on mine but only done 74,000 odd miles....

Hi

I was surprised that your car had only done that amount of mileage yet the flanges had corroded to nothing,mine as done 185k and only one side as gone the other is corroded but as life in it yet,I suppose a lot as to do with the conditions and salt that may have been thrown onto the flange when driving in wet conditions,as my car never saw snow that could be the reason they have lasted 22 years and 185k.Anyway I am off to see my engineer tomorrow who is going to braze up the pipes I will stick a pic on if it goes well.

39buss · July 2, 2012

I dont have an LS but this sounds like an awkward job to do, so dont shoot us down for this. Can the flanges/bell ends be cut off with an angle grinder and a sleeve made 2-3" long, using exhaust pipe with an internal diameter slightly larger than the external diameter of the LS pipe so it slips over and can be mig welded in situ. Dont like the idea of brazing, open oxy/gas flame under the car and it may fracture in use,vibration etc.

ambermarine · July 2, 2012

I dont have an LS but this sounds like an awkward job to do, so dont shoot us down for this. Can the flanges/bell ends be cut off with an angle grinder and a sleeve made 2-3" long, using exhaust pipe with an internal diameter slightly larger than the external diameter of the LS pipe so it slips over and can be mig welded in situ. Dont like the idea of brazing, open oxy/gas flame under the car and it may fracture in use,vibration etc.

Short answer no,there are no straight runs on either the cat or the y pipe longer than 10 mm the flanges were welded to the virtual ends of the cat and the y pipe which is angled and seam welded on the fold.

I understand your concern about the oxy/ace torch but with the right nozzle and silver solder the fracture possibility is reduced and mig welding could be a bit too aggressive in such a confined area, resulting in holy pipe.The area concerned is covered in heat shields protecting the body of the car from the exhaust system that should help illiminate fire risk plus I will be on standby with a fire extinguisher. The Exhaust system is supported quite extensivly, testimony to the fact that the flange area is not blowing yet although 70% of the flanges have disappeared.According to a previous poster who as broken Many LS400's this is the common fix as they reach there last years of life.