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Blown exhaust manifold gasket


cliff.b
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Spit 1500 manifold gasket blown and replacement ordered but had planned to use car this weekend.

Has anyone had any experience of any product or "bodge" to make a temporary, effective repair for a few days?

Is "Gun Gum" (which I already have) up to the job?

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It may work. and there are also bandage type fixes that you could wrap the joint with. You may get lucky.

BUT be warned, the reason for the blown gasket could (likely) be (1) studs.nuts poor, loosing grip. Removing nuts may snap a stud. (2) uneven faces on the manifold and/or downpipe

Put it this way, if you don't want to use the car as is, and you need to take the old gasket out, you will then find out. This is the sort of job that looks easy, and ends up with taking the manifolds off etc to fix. Be warned!

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Gungum type stuff may temporarily fix a small leak in the exhaust but I really can't see any chance of it helping a blown manifold gasket unless smeared over both faces, which would involve removing the manifold so just replace the gasket and I would have new nuts and a couple of studs available. You may well be able to get everyting from an MG garage quickly as well just tell them it's for a midget 1500

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As a temporary fix, to fill a hole for a few days, clean it well - carb cleaner works quite well - then pack with exhaust paste, smear more paste around the joint, then cover with a good exhaust bandage and tie with metal ties above and below. It will work in the short term - make sure you do use the bandage otherwise it will probably blow out again - but as the guys have said there'll be an underlying problem that caused it in the first place. Count on having to replace studs and nuts, maybe smooth down the faces of manifold and exhaust flange, but be careful of what studs you buy. One of the last sets I went for was made from shiny silver cheese. Spalding Fasteners supplied heavy duty versions which were excellent.

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The advice above is spot on.

One other little tip... Don't wait for the new gasket to arrive, start squirting the manifold/downpipe nuts and studs with penetrating oil now, and repeat every few hours to give yourself the best chance of removing the nuts without snapping the studs. Use a proper penetrating oil like Plus Gas or the there's a 3 in 1 version that works well. Don't use WD40, although it's great as a water dispersant, it was never meant to be a penetrant.

One other tip if the nuts are stubborn is to heat them with a blow lamp but be very careful of the carbs and petrol nearby.

Nigel

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Ok, I have taken a look and getting the nuts/studs out wasn't a problem because none of them were tight, despite me tightening all of them a couple of months ago. I suspect this may be the problem🤔.

On inspecting further I found a distinct lack of lock washers, and in fact the middle fixing was a nut and bolt that was too short to have any fitted. Also, the front hole in the manifold had a crack across the hole and the corner fell off when the nut was loosened.

I prised the joint apart a few mm and forced gun gum all around, fitted new bolt & wagers and everything had tightened up, even the damaged corner.

I will tape it up & try it later but wondering now if I will need a new manifold 😒.

 

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1 hour ago, cliff.b said:

Ok, I have taken a look and getting the nuts/studs out wasn't a problem because none of them were tight, despite me tightening all of them a couple of months ago. I suspect this may be the problem🤔.

On inspecting further I found a distinct lack of lock washers, and in fact the middle fixing was a nut and bolt that was too short to have any fitted. Also, the front hole in the manifold had a crack across the hole and the corner fell off when the nut was loosened.

I prised the joint apart a few mm and forced gun gum all around, fitted new bolt & wagers and everything had tightened up, even the damaged corner.

I will tape it up & try it later but wondering now if I will need a new manifold 😒.

 

With the cracked section, yes, a new, or good used one, is a good idea. However, make sure it has new studs fitted, and as above, not made of cheese. Also worth finding "longer" brass nuts to suit, I have sourced these through fleabay and they are much better than "std height" brass nuts. Don't even think about steel nuts... 

The nut/bolt you found is probably because a stud broke previously, and was drilled out. I have done the same in the past. In fct, the last 1500 anifold I had I drilled all the studs out, and tapped to M10 (3/8 UNC would be better possibly) then used cap head bolts that could be done up tight. With both surfaces filed flat, there were no more blown gaskets after that.

 

OR for the best fix, fit a 4 branch stainless manifold. All the issues go away.

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Are we talking the manifold to head gasket here (as I assumed) or the pesky manifold to exhaust. If the latter just get a 4 branch as you will have to replace the manifold, might be worth it in either case I don't have the issue as the mk2 had a 4 branch as standard.

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50 minutes ago, clive said:

fit a 4 branch stainless manifold. All the issues go away.

... to be replaced with other issues of poor fit, lack of clearance, increased noise, etc.  Not that I disagree - I opted for the 4-branch on my 1500 Mk3 because I didn't have a 1500 manifold to start with, but some chassis mods were needed to make it fit.

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34 minutes ago, DanMi said:

Are we talking the manifold to head gasket here (as I assumed) or the pesky manifold to exhaust. If the latter just get a 4 branch as you will have to replace the manifold, might be worth it in either case I don't have the issue as the mk2 had a 4 branch as standard.

Yes, I should have clarified that it is the manifold to downpipe joint blowing and the front corner of the manifold flange has cracked across the hole.

 

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3 minutes ago, NonMember said:

... to be replaced with other issues of poor fit, lack of clearance, increased noise, etc.  Not that I disagree - I opted for the 4-branch on my 1500 Mk3 because I didn't have a 1500 manifold to start with, but some chassis mods were needed to make it fit.

I'm thinking I will look out for a used standard manifold and get new studs/bolts etc. Taking all the above advice into account.

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1 hour ago, Mark B said:

Make sure the exhaust down pipe is supported at the bottom of the gearbox bell housing.

It's not currently and I was thinking it should be. Where does the bracket attach?

Is it actually to a bellhousing bolt?

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57 minutes ago, Pete Lewis said:

Ahh, yes. Looks like I need the exhaust mounting bracket which it says is no longer available. 

Will have to try and make something suitable.

Temp repair now in place and continues to seal after car driven about 20 miles.

I think I may need to take it out again later, just to be sure it's ok 🤔

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On 23/09/2021 at 17:15, cliff.b said:

Ahh, yes. Looks like I need the exhaust mounting bracket which it says is no longer available. 

Will have to try and make something suitable.

Found this one yesterday on a (very oily) Herald, attached to the rear of the gearbox... might give you an idea of what to fabricate?

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2 hours ago, Colin Lindsay said:

Found this one yesterday on a (very oily) Herald, attached to the rear of the gearbox

That's not the only one on a 1500 Spitfire. They do have that one, by the looks of it, but they also have one supporting the Y-piece at the engine backplate. It's that backplate one that prevents movement of the downpipe flange and thus helps with gasket life.

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Many thanks both. My car has a non standard exhaust with the silencer secured to the boot floor underside by 4 bolts with rubber cushions. And that's it, nothing between that and the manifold.

Clearly one supporting the Y of the downpipe makes sense and probably another between that and the silencer.

Despite this though, I have been away for the weekend, covering over 150 miles and my temporary manifold/downpipe repair has lasted ok.

Think I need to decide what I'm going to do and get/make all the bits before sorting the entire exhaust properly.

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1 hour ago, cliff.b said:

Many thanks both. My car has a non standard exhaust with the silencer secured to the boot floor underside by 4 bolts with rubber cushions. And that's it, nothing between that and the manifold.

Clearly one supporting the Y of the downpipe makes sense and probably another between that and the silencer.

Despite this though, I have been away for the weekend, covering over 150 miles and my temporary manifold/downpipe repair has lasted ok.

Think I need to decide what I'm going to do and get/make all the bits before sorting the entire exhaust properly.

The support off the diff is the most important one. I use an old fashioned rubber strap/hanger, bolted to the diff, and a 90degree bracket at the other end which is in turn clamped with a U bracket/clamp to the pipe. 

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