Volvo 960 / oil the throttle body & manifold / PCV

[AntoineBa]

Hello everyone,

I noticed that in my Volvo 960 2.5 l 1995, I can find oil in the inlet manifold and in the throttle body, and that the oil consumption of the car in higher than it should.

I have done the glove test for the PCV system but did not notice excessive pressure from the crankcase.

Anyway, at Christmas I will service the PCV system, as I already have bought the parts (not really looking forward to it, as it seems a painful operation).

The car is also equipped with an EGR valve that I am planning to clean.

To your knowledge, could there be a clogged pipe / channel in the PCV system that would force oil from the crankcase to the intake manifold without provoking excessive pressure, or should I expect something more serious (piston rings) about this oil flood? Could there be a relationship with the EGR valve?

The thermostat of my air box was dead and the flap was set to 100% hot air, smaller diameter input (3.5 cm diameter vs 6.5 cm for the cold air), so the car was missing air volume at higher revs, but I doubt there could be a link between this and the oil in the intake.

Thanks & Regards,

Antoine

[Piet22]

The flap is operated by a wax-cartridge on the bottom of the airbox.
If yours is still the original it is almost certainly dead now.
Part nr is 1266826

[RollingThunder]

Its normal to get some oil in the throttle body - how much are you seeing?

This is the throttle body of my last whiteblock engined car, an S70 T5, before I cleaned it -

[AntoineBa]

Thanks, indeed, it is this small thermostat which failed, leaving the flap on 100% hot air. Mine is very similar, but not exactly the same, as in my air box, it needs to be bolted. I cannot find it, but in the meantime, I have secured the flap to 100% fresh air using a nail to replace the thermostat shaft.

[AntoineBa]

My throttle body was as dirty as yours, but more generally, there is constantly a certain amount of oil at the bottom of the intake manifold, and also traces of oil in the duct between the MAF sensor and the intake manifold. On a 960 group on Facebook, I have been replied that all 960s have this issue, as the breathing system of the engine is undersized, so this is pretty reassuring.

[RollingThunder]

Indeed. I used a 5/8" hose instead of the smaller diameter OEM Volvo part. Its a pretty standard mod



If I was doing it again I'd use some copper pipe rather than the hose as it was a PITA trying to fit it under the manifold without kinking it and causing a restriction - which would defeat the object of the mod

These are the holes which commonly get blocked - in this case they were surprisingly clear.



I've usually found them to be literally 1/2 blocked when replacing the PCV system. It all depends upon maintenance and whether a good quality fully synthetic oil has been used.

[AntoineBa]

It is a good idea to increase the size of the pipes. The person on the 960 group on FB has added an oil catch can between the intake and the breather box. Thanks for those pictures, I am planning to service the PCV system on my car at Christmas, and really not looking forward to it, as it seems rather painful. By the way, once you put the inlet manifold back, do you add any liquid sealant in addition to the paper gasket? I have seen on the Volvo service manual that the torque recommended to bolt back the manifold is 20Nm, it does not seem much.

[RollingThunder]

No sealant, just fit it dry - thats how the factory did it.

Tbh I don't torque up those bolts as such - I just tighten them up by feel, bearing in mind its an aluminium head. They are done up *tight* though. Probably best to torque them if you're not sure. According to Haynes, the intake manifold bolts should be torqued to 20Nm.