Are 940 B230FK exhaust mainfolds a common crack failure?

[eeedelli]

Hi all,

I don’t use my 940 celebration much (LPT, B230FK) – more as a spare/'for best'/long-runs car really. (My daily shed remains my old 740, though fresh water ingress from somewhere I can’t find (not antifreeze/water valve) is rusting the floor out so it might not be around much longer )

Anyway over the last couple of months, I’ve noticed the 940 starting to ‘tick’, particularly for the first minute or so after start-up and, after wondering whether I was getting an oil supply problem to the cam, realised that it’s exhaust gas leaking, until the temperature warms up and re-seals while idling. (You can smell the rich exhaust fume under the bonnet during that brief time.)
It’s also getting quite noticeable when putting the power on (revving, accelerating, driving at speed, going up hills etc) - pretty much anything other than just idling.

I’ve tried using a listening tube to isolate it but the nearest I can say is that it seems to be around cylinders 3 or 4. The heat shield, downpipe and turbo make it difficult to get all around the ports with a listening tube.

I’m just wondering whether the 940 B230FKs are a known problem with exhaust manifolds cracking or whether it’s more likely to just be a gasket (though why that should suddenly fail seems a bit odd).

Either way, it looks an absolute pig of rusty studs to get off. It’s probably not done 1000 miles since I rebuilt the turbo and replaced the downpipe and all the oil cooler seals and coolant hoses etc and I know it was murder trying to juggle the oil pipes on to the turbo so I’m not looking forward to that again!

In view of the fact that it's so nearly sealing, I'm wondering whether it might first be worth just whipping the manifold nuts off, cleaning the studs (if possible in-situ), replacing with new brass nuts and re-torquing them to try to achieve a seal, assuming it's not a crack.

Any suggestions?

Ta,
David.

[Arewethereyet]

Yep, they crack alright. You can repair it however

[Clan]

Originally Posted by eeedelli

Hi all,

I don’t use my 940 celebration much (LPT, B230FK) – more as a spare/'for best'/long-runs car really. (My daily shed remains my old 740, though fresh water ingress from somewhere I can’t find (not antifreeze/water valve) is rusting the floor out so it might not be around much longer )

Anyway over the last couple of months, I’ve noticed the 940 starting to ‘tick’, particularly for the first minute or so after start-up and, after wondering whether I was getting an oil supply problem to the cam, realised that it’s exhaust gas leaking, until the temperature warms up and re-seals while idling. (You can smell the rich exhaust fume under the bonnet during that brief time.)
It’s also getting quite noticeable when putting the power on (revving, accelerating, driving at speed, going up hills etc) - pretty much anything other than just idling.

I’ve tried using a listening tube to isolate it but the nearest I can say is that it seems to be around cylinders 3 or 4. The heat shield, downpipe and turbo make it difficult to get all around the ports with a listening tube.

I’m just wondering whether the 940 B230FKs are a known problem with exhaust manifolds cracking or whether it’s more likely to just be a gasket (though why that should suddenly fail seems a bit odd).

Either way, it looks an absolute pig of rusty studs to get off. It’s probably not done 1000 miles since I rebuilt the turbo and replaced the downpipe and all the oil cooler seals and coolant hoses etc and I know it was murder trying to juggle the oil pipes on to the turbo so I’m not looking forward to that again!

In view of the fact that it's so nearly sealing, I'm wondering whether it might first be worth just whipping the manifold nuts off, cleaning the studs (if possible in-situ), replacing with new brass nuts and re-torquing them to try to achieve a seal, assuming it's not a crack.

Any suggestions?

Ta,
David.

When you hear a chuff like that which gets better when hot it is usually a port gasket , You think it a tricky job ? you should try it on the recent engines ! It was a piece of cake back then . Buy a new set of genuine volvo manifold studs and nuts before you start .Then try and torque them up to the correct figure.

[eeedelli]

Originally Posted by Arewethereyet

Yep, they crack alright. You can repair it however

Oh. I thought welding cast iron was extremely difficult?

[eeedelli]

Originally Posted by Clan

When you hear a chuff like that which gets better when hot it is usually a port gasket , You think it a tricky job ? you should try it on the recent engines ! It was a piece of cake back then . Buy a new set of genuine volvo manifold studs and nuts before you start .Then try and torque them up to the correct figure.

I can imagine! I don't have much desire to move on to the newer models before absolutely necessary, as all manufacturers seem to have a knack for making things almost impossible to work on these days!

Do you think it's worth trying to nip up the existing gasket first?

[classicswede]

My money would be on one of the cracks in the manifold leaking a little when cold. Gasket leak is possible. I would suggest taking the manifold off to look and get it welded if needed

[Laney760]

Originally Posted by Clan

When you hear a chuff like that which gets better when hot it is usually a port gasket , You think it a tricky job ? you should try it on the recent engines ! It was a piece of cake back then . Buy a new set of genuine volvo manifold studs and nuts before you start .Then try and torque them up to the correct figure.

I've owned my B230FK for over 6 years now and in that time my exhaust manifold bolts have loosened and caused a leak of gases no less than three times! Can overtightening them cause a cracked manifold?

[classicswede]

Originally Posted by Laney760

I've owned my B230FK for over 6 years now and in that time my exhaust manifold bolts have loosened and caused a leak of gases no less than three times! Can overtightening them cause a cracked manifold?

No it will not make the manifold crack, that not where the develop cracks. The cracks start behind the turbo in the collector area.

If the nuts are coming loose I would check teh correct type of nuts and washers are being used. Also make sure the bracket from teh downpipe to the block is still fitted as without that more stress is put into the turbo and manifold

[Clan]

Originally Posted by Laney760

I've owned my B230FK for over 6 years now and in that time my exhaust manifold bolts have loosened and caused a leak of gases no less than three times! Can overtightening them cause a cracked manifold?

It is essential to use volvo studs and nuts and gaskets and torque them to the correct figure , this was not a problem when the cars were current . a cracked manifold is caused by many years of expanding and contracting . after a hard run up a long hill the manifold will be glowing red it can have a hard life , if you can find a new manifold it will cure the problem ,
I would even investigate the suitability of studs and nuts from one of the later petrol turbo engines , they have a small hexagon on the end which helps in removing and fitting .Only length may or may not differ .

[827Roverman]

Originally Posted by eeedelli

Oh. I thought welding cast iron was extremely difficult?

Your quite right, welding cast is difficult, if you find it does need welding get a specialist to do it, don't let anyone try and mig weld it.