Cracked manifolds and turbos

[940_Turbo]

I decided today to have a look at a cracked manifold on a 940 Sports edition. I guess we all know by now that the manifolds crack, but fewer people have taken a look at the turbo itself. Gradually the waste gate housing eats itself and the car starts to lose boost.

The cracked manifols can be quite spectacular, the one below is actually off my own car which has a lot of Autobahn miles under its belt.




The first step is to find a decent waste gate housing. Mark was lucky to track down a virtually unused turbo down. it had been fitted to a car to cure a running problem only for the owner to discover the engine was fubarred....



Split the waste gate from the turbo cartridge. It is held on by a v band, all it takes is to loosen off the bolt and unhook the waste gate actuator arm. Put the turbo in a safe place. If you bend its exhaust wheel you'll cry. You'll be left with this.




The turbos can be equally horrible; the inlet by the manifold cracks, but it doesn't seem to be a huge issue for them.



Worse is that the waste gate seat disappears, no seat, huge boost leak, loss of power. The waste gate housing can be bought new for about 80 quid on ebay. They're fairly easy to change.




I decided to do a bit of porting in order to try and reduce the hot spots. My own 940 runs on gas and the waste gate housing and manifold have stayed intact so far.

Fist up is the exhaust, below is how it looks standard.



The oval hole can be opened up round. You need to leave a l;ip for the turbo to seat against.

Here is is part finished, and finally finished and back on the car.






Next is the turbo, the standard oval hole will be opened out and matched to the manifold.



The aim is to alleviate hot spots, if the gas flows freely it'll carry the heat with it. Pay attention to the high spots by the waste gate and make them flow.



I also like to open the waste gate hole itself out slightly. Some are really restictive, others are better. Spray a bit of paint round the waste gate flap to show you how much metal you have to play with. Compare this with the image og the molten seat above.



this still needs a little tweaking, but you get the idea. Finally the turbo is sealed to the manifold with the oft claimmed not to exist Volvo gasket. 940s indeed have no such gasket, 850s do, here it is for your edification.

[TonyS9]

Very useful, I didn't think it could be helped. I cracked my Turbo with a speedo reading of 140mph at 11psi, well it broke into the water cooling jacket at that point as I noticed a large cloud behind me. Think my manifold might be cracked aswell.

Might try some of the mods on my 360 project.

[940_Turbo]

If there were clouds of steam you've killed something in addition to the waste gate housing. The housing isn't water cooled, only the turbo cartridge itself.

Head gasket is a strong candidate if something sudden and catastrophic happened.

[jamies volvo]

Thanks for that one,been wondering about changing the head gasket for a second time untill i read this.might not have to bother now after all

[TonyS9]

This was years ago, I thought the housing was watercooled at the bearing and it had circular cracks around the curve. It would also weep water when cold and you could hear the spinning more. It lasted another few years before becoming a pain. I did the full skim and turbo replacement then.

[Oilydad]

Very useful post, and thanks to Volvo 940 for the pictures.

I have taken the liberty of enhancing them on my PC, as I found some of them very difficult to actually see them. So here are the same pics, but with a lot more detail.

[Steve940estate]

Yes very helpful. I've just bought a manifold to turbo gasket for my car. One thing I did find was that they are listed for early V70s on Vadis so it took a while to find.
I will take a few photos of my welded manifold as well. Time will tell how it lasts but it was done by a good company who know their stuff.

[rogerthechorister]

Very useful fred.