Manifold Leak Suggestions Please
 

Over the last 4-5 days noticed that it seems my 940 2.0 Turbo has sprung a smallish leak on the exhaust manifold.

With the awful weather today, this rather put me off doing any further tracing, so will look to do this tomorrow. Bit concerned, as I'm pretty certain the mpg has definitely dropped, and forum seems to indicate this needs swift attention as engine is over fuelling, possibly leading to damage to cat.

After initial brief look yesterday, it sounds somewhere around manifold or turbo but engine was still hot so couldn't really investigate. Downpipe definitely has the bellhousing bracket, will check tightness tomorrow.

Would appreciate any thoughts on best way to track down the source of the leak, I am thinking of sticking my shop vac onto blow, and see if I can pressurise the system slightly and squirt some soapy water around joints on cold engine? Have looked at exploded parts diagram on GCP but cannot figure out if there is a gasket between manifold and Turbo, and also Turbo to downpipe joint??

Forum seems to advise that manifolds may be common source for cracking, also seems a lot of thumbs up for genuine Volvo studs and nuts, they are a bit pricey though. Was thinking stainless would be a better option as way cheaper from specialised fastener suppliers.

Hoping it might be Turbo to downpipe joint, so I don't have to faff around and remove Turbo / manifold, and then have to mess around with Turbo oil pipe, the more needs removing, the more possibilities for me to cack it up!!!!

Preparing for worst case, or me just being a pessimist, assuming the manifold has cracks, anyone used JB Weld Extreme Heat Putty, seems good reviews, but my gut feel is it's a bodge. Brother In Law is a bit of a demon welder with MIG, TIG, and Oxy/Acetylene, anyone had success grinding cracks and welding or brazing?

If cracking is common, them probably sourcing one off EBay not really a great idea??

Cheers
Steve

If its cracked and you know a good welder then definitely get them to sort it , have read on a few places that opening up the manifold flange and turbo flange help it flow a lot better and keep it from getting so hot, if thats true im not sure.

No gaskets on the turbo to downpipe or the manifold to flange, but you can use later cars but its desgined to not need one.

you can try looking for white staining on the manifold will be where it is leaking

Many thanks Jesus,

Yes I recall now some posts suggesting using gaskets used on 850's I think.

Just seem to recall always being told that you can't weld cast iron, but I suppose on something like a manifold, all we need to do is make it airtight.

Good tip about white staining, so I'll get good inspection light and mirror to see if I can find the source.

Cheers
Steve

J.B.Weld is a very useful product but it wont stand up to the manifold heat:~
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Welding cast iron needs someone who knows what they are doing and is a specialized task. Brazing however is a process that works requiring less heat- I've used it on classic manifolds with no problems.
Good Luck
Bob.

Many thanks Bob,

Yes I have some normal JB Weld in the garage, but had not been aware of Somethimg called JB Weld Extreme Heat, supposedly good to 1000F or 537 C and stated as good for manifold cracks??

If it is the manifold cracked, it might be tempting using this first to save pulling Turbo etc. If it fails, then just have to get brother in law to see if he can weld or brake it I think.

Yes I had always thought cast couldn't really be welded, I think specialists do stitch repairs to things like blocks/heads etc. Never needed before so who knows.
T'internet is a bit of a Wild West of opinions as a quick trawl last night returned several posts from someone just using big standard Mig settings to someone using special expensive wire.

Not sure if brother in law has brazing tip or not, would a special rod be needed to braze cast iron??

Cheers
Steve

Steve:~
Brazing is done with bronze rods & flux- gas welded.

The last one I had repaired had been by a blacksmiths shop (Nr Southport) but the technique isn't completely lost so worth checking via fabricators or a descent engineering welding services.
It has the advantage that if the casting is a low grade one brazing should still repair it.
You may be lucky and find its a blown gasket- fingers crossed!
Otherwise the above is a good working option.
Regards Bob.

The Extreme Heat JB Weld won't stand up to the temperatures in a turbo exhaust manifold Steve. :nah: If it's only good for 537C, i doubt it would stand up to standard exhaust temperatures as generally the exhaust flame is ~650C. Would be a waste of your time and money, not to mention your BILs time when he comes to do the proper repair if it has cracked.

I'm no expert on cast iron welding but i believe the procedure is to preheat it to ~200C in an oven, weld it then get it back into the oven for a few minutes before switching the oven off so the oven and manifold cool down slowly and evenly. This apparently helps prevent cracking as it cools.

If you look on ebay.com (the USA part of ebay) for OBX exhaust header for turbo 940, you should find a nice tubular stainless exhaust manifold. It will relieve you of lots of $$$$ and take some time to get here but will help release a few horses and should be gas tight.

I'd advise against using stainless exhaust studs in the aluminium head, it's bad enough with mild steel but from what i remember, there's a worse electrolytic corrosion situation with stainless in the aluminium head than mild steel. Either way apply copper grease to the studs before fitting and also to the nuts - you could use stainless nuts on mild steel studs if you want as the stainless would be separated from the aluminium head.

Hi Dave,

Once again many thanks for the clarifying a number of points, and fully appreciate the putty shortcomings now you've outlined them, it was my initial feeling it would be a bodge.

Will see what I can track down today, hopefully the leak is at one of the joints rather than cracked manifold.

Your suggestion of tubular manifold is interesting option, as late last night I had a similar thought if I could get my BIL to fabricate one (probably need more than a few beers though😀). I did find some suppliers where you can source various bends, obviously would need a lot of work slicing these up and welding together again, but he does have a massive power bandsaw that can cut precise angles.

Interesting project to ponder perhaps once weather improves.

Will update once I get under the bonnet, hopefully I can cobble something together to find the source.

Cheers
Steve

You could give Martin at Viking Fabrications a shout as he is very good at custom stuff.

Hi Mark,

Good shout for a possible fabricator, think the wallet is shuddering at the thought 😀😀

Cheers
Steve