Blowing Manifolds

[Katana550]

Hello again all,

I have yet another problem:mad:

After a new exhaust system was fitted the exhaust manifold started blowing at the junction with the head.

I stripped all the manifolds off; cleaned all surfaces and faces to a (I hope)perfect order.

I then, with the aid of new gaskets and a combination of exhaust sealing putty and blue hylomar (using only a very light smearing in the appropriate places) rebuilt the whole lot using all the correct torque settings.

Within 100-odd miles the blowing was back:banghead:

So, I went through the whole process again; again with new gaskets and a spot more sealant at the position of the blow. This actually appears to be at the top of the two central exhast ports - there didn't appear to be any blowing (telling from the burn/gas marcks left) at any other place.

Again within 100-odd miles the blowing returned :banghead: :banghead: :banghead: This is driving me mad!!!!

Can anyone provide details of their experiences and/or some adise or hints on how to solve the problem or where I may be going wrong??

Thanks

Tim

P.S When I took the whole lot apart the (I believe it is) Induction Heater which bolts into the Inlet manifold rattles - I assume this means it is knackered!! How much is one and how important is it??

[tony]

a short and sweet post this one,i had a mini with the same problem that turned out to be the engine and gearbox mount that had gone soft and that alould the engine to rock when reved ,thus breaking the joint on the exhust manifold :)

[E_T_V]

I believe Jon had/has a similar problem with his 2.0.

[Jonathan]

This all sounds very familiar indeed! At the moment I'm not in a position to offer any constructive advice on the subject because it has rendered my MG undriveable for the last couple of months.

I found the job so unpleasant I got a professional mechanic to do it for me... twice. I thought I had everything tightened to the correct torque the first time but there was still a visible gap between manifold and head because the bars that support it were getting in the way. All surfaces must be completely clean and even, it might be worth checking the manifold hasn't become slightly warped?

[G Force]

Hello there, I have seen quite a few manifolds that are warped and this could be your problem. I would recommend that you do the gasket one more time, but do not use any sealants at all they are not necessary. Once the engine has run and been up to full temperature try re-torquing all the fixings.

The inlet manifold heater is there to improve drivability when cold and during warm up. If it is not working you may find that you experience stalling whilst the engine is warming up and poor running when cold.

Cheers Gary

[Jonathan]

Originally posted by G Force
The inlet manifold heater is there to improve drivability when cold and during warm up. If it is not working you may find that you experience stalling whilst the engine is warming up and poor running when cold.


Again, this sounds very familiar to me, and opens up a new line of enquiry in my case - thanks for raising it. Mine has a very erratic idle and tends to stall when cold. In fact it's got to the point where it can barely be started at all. One more thing to check before I replace every single mechanical part in the car :)

[e692wtt]

If memory serves (and very often, nowadays, it doesn't...) only the 1.6 and 2.0 carb-equipped engines have this Inlet Manifold Heater, not including the Turbo though. You can tell if it's working as it will draw approx 16 Amps, ie try unplugging it when the engine is just started and listen to the revs rise... it draws that much current! Or use a multimeter that will cope with, say, 20 Amps.

So an Injected engine with poor cold running has problems elsewhere, sorry Jonathan.

[Jonathan]

At least that rules something else out ;)

[Katana550]

Hello again all,

Well, just in case any of you are sad like me and want to know the final solution to the B***dy annoying blowing exhaust manifold problem, here goes:

Having gone through three manifold strip and rebuilds the solution was reached on the fourth attempt:banghead: :banghead: :banghead:

Use TWO gaskets.

But not the ones that are built from a metal substrate with a black (paper?) cover each side. Use the grey fibrous construction type.

Ensure that all mating surfaces are as perfect as possible - access to an engineers bench would have been helpful here:rolleyes:

I tightened all the retaining bolts and nuts to 25Nm+ as opposed the the (Haynes) recommended 20-22Nm.

I then had to check and tighten (I forgot the B***dy locknut - but would this be any use in such a high-temp location?) the nuts and bolts every 100 miles about 6 times.


Now every thing seems to be ok!!!!:eek: :D :cool:

I don't know whether this will help any one but the difference in the gaskets seemed important.

Tim

[E_T_V]

Funnily enough using two gaskets was what I suggested to Jon and someone else I think.. Glad to know my hair-brained ideas sometimes aren't too far wide of the mark..

Glad it is all sorted