15 replies to this topic

[Jim_C]

City E 998 with Stage 1 exhaust kit
1986


I've just bought a mini as above, and over a 70-mile drive it became clear that either the exhaust downpipe, the manifold or one of the gaskets was blowing progressively. Once home, I looked to see if I could see where the leak was, and the gas appears to be coming from the area ringed here:



At first I thought it was coming from the inlet manifold (mighty puzzling), but I'm guessing it's more likely to be the central exhaust gasket that's gone. Isn't it...?! Any help much appreciated.

Would the blown exhaust gasket/manifold account for the big low-down flatspot accompanied by coughing and spluttering that the car also has, as well as a seemingly over-rich mixture (black sooty exhaust but no oil burning)?

Thanks in advance for all help/advice. Also, sorry if this is a common fault - I promise I searched!

[jaydee]

Make sure that its blowing there and not where exhaust manifold links to centre pipe and gearbox.
Check that manifold to head nuts are tight and, if gasket is worn, replace it as it costs 1/2 quid.

[Pauly]

Get a bit of tissue and place it over where you think the leak is and see if it flickers. If its the manifold gasket, then it can cause an air leak which would lead to the problem you are having.

See you have a stage 1 kit, has it been tuned at all? If not this will also contribute to your problem.

Paul.

Edited by Pauly, 07 July 2009 - 03:37 PM.

[Jim_C]

Thanks for the replies; I only got the car on Saturday and the person selling it had no idea of its tuning history (selling on behalf of owner), except that it was put through its MOT recently.
I can feel the gas emerging in the gap between the arms of the inlet manifold, plus there is some soot build up there, so I think it must be from directly below there...

[m1tch]

It might perhaps be the rocker cover gasket that has blown out a bit, the rocker cover is slightly pressurised, hence the gasket, take the rocker cover off and re-align the gasket (or indeed get a new one lol) this might help with the running of the car as well, as losing crank case pressure can't help

It might explain why you can feel gas escaping from round there, and why it might not be running right!

Edited by m1tch, 07 July 2009 - 03:54 PM.

[Nightrain]

It's because of the thickness in the flanges, the alloy inlet been a lot thicker. Means the centre exhaust isn't clamped up tight ! You need to either step the thick washers or weld/tack half washers to the exhaust flange to make up the difference.

[Jim_C]

@ M1tch - it could be the rocker cover, but I don't think that would account for the noise...

@Nightrain: I'm probably being thick, but I don't see why there would need to be any connection between the inlet and exhaust manifolds where they tighten to the cylinder head, so why does the increased thickness of the flanges on the alloy inlet matter? No wonder I'm not a mechanic...!

[m1tch]

@ M1tch - it could be the rocker cover, but I don't think that would account for the noise...

@Nightrain: I'm probably being thick, but I don't see why there would need to be any connection between the inlet and exhaust manifolds where they tighten to the cylinder head, so why does the increased thickness of the flanges on the alloy inlet matter? No wonder I'm not a mechanic...!

The mini manifolds share a common manifold gasket and also share common bolts when fastening them lol they are held on with a bolt and a large washer that goes over the sides of the 2 manifold flanges - not a common design as modern cars have cross flow cylnder heads lol

[lrostoke]

I'll go with Nightrain

That looks like an MG Metro inlet manifold. We fitted one recently and when fitting we noticed that the sections of the inlet manifold the manifold washers and nuts clamp against is thicker on the inlet manifold than it is on the exhaust manifold.
So what happens is that the washers tighten down the inlet, but don't clamp down on the exhaust, so the exhaust isn't fully tight against the head.

We cured it by filing down the alloy inlet so the tabs were same thickness as the exhaust tabs.

Also there are 2 holes plugged on that inlet, that big plug (servo take off) and a smaller plug, make sure they are plugged tight and not leaking, otherwise they will suck air in and screw the mixture

Different manifold, but more or less the same, you can see the bolting tabs either side of the inlets (bottom of picture), they are probably thicker than the ones on the exhaust manifold

Edited by lrostoke, 07 July 2009 - 05:06 PM.

[Nightrain]

@Nightrain: I'm probably being thick, but I don't see why there would need to be any connection between the inlet and exhaust manifolds where they tighten to the cylinder head, so why does the increased thickness of the flanges on the alloy inlet matter? No wonder I'm not a mechanic...!

As steve said above, the thicker alloy flange holds the thick washer off the thinner exhaust manifold.

[Jim_C]

Blimey, I'm learning fast! Thanks guys. The bit I didn't get was the shared gasket and bolts, otherwise I couldn't see why you couldn't tighten the inlet independently of the exhaust manifold. It seems bonkers that the people fitting the new inlet manifold wouldn't have noticed this...

So, is the best answer to grind down the inlet manifold flanges, tack/weld half-washers to the exhaust flange or source a new manifold combo. If so, which should I keep and which should I bin...?

God, and I thought the Fiat Coupé was complicated...

Thanks once again,

Jim

[smoggy_clubman]

Ive got the exact same problem! When i got my car it got worse and worse as i drove on! Tried tightening them up and bent one of the studs as there was that much of a step! Got new studs and gasket and i think im just going to file them level
ste

[lrostoke]

So, is the best answer to grind down the inlet manifold flanges, tack/weld half-washers to the exhaust flange or source a new manifold combo. If so, which should I keep and which should I bin...?

Nothing wrong with that type of manifold, so which ever is easier for you, half washers, or file down the alloy tabs.

[rick.spi]

in the first week i had my mine the exhaust gasket went and thinking it would be alright i kept driving untill the weekend when i planned to fix it...then it started sucking in air at the manifold, then it conked... wouldnt start untill you left it to cool down for 15mins or so then u could go a lil more, had to get all the way home like this. then i was off the road till the gasket came (was already ordered when i first found it blowing)

well it a pointless story but basically im trying to say get it done asap as it can get a fair bit worse lol.

[Cooperman]

That is such a common problem with after-market manifolds. Just file down the flanges on the alloy inlet until they are the same thickness as the exhaust manifold flanges and bolt up with a new gasket and it'll be fine.
It's more of a problem when the exhaust flanges are thicker than the inlet flanges, which often seems to be the case with a twin SU standard inlet manifold and an LCB exhaust. Then you get air into the inlet and it just won't run properly. it's then more difficult to get the ex. manifold off again to file it down to match the inlet.
Ah, the fun of Minis!