Engine: 2.3 F/Inj B23E/B230F: Exhaust Manifold Gasket Leaking

[TheHungriestBadger]

Hi all,

Been sitting on this one a while, but I think my manifold gasket is leaking. I've recently gone through the codes on my OBD box (1990 Volvo 240, B200F LH2.4) and found a stored 2-3-1 code which, according to this page corresponds to a fuel mixture too rich/lean condition when at part load (i.e. cruising). This is the only code I have.

My only other symptoms are that I can feel air 'pulsing' from the exhaust side of the engine (definitely when cold, not sure about when hot), and I have a sort of 'ticking' sound when the engine is under load and up to temperature (I've had this for the last ~2k miles so can't be too catastrophic). And no it's not piston slap, although I do have some of that only when the engine is cold which is 'normal'.

I don't have a check-engine light displayed, and I know that the bulb works as it comes on with the idiot lights when the key is first turned to KP2. I also don't have any driveability issues, and managed 32mpg on a run not long back (not bad for an auto, right?).

My next steps thus far will be to check the condition of the spark plugs which should indicate whether the engine is running rich (upstream exhaust leak?) or lean (intake-side/vacuum leak?). I'll also check the O2 sensor signal at the plug in the engine bay as well to verify it's not just the sensor that's had it. I may also try clearing the code by removing the eECU fuse and see if it comes back.

Any faults in my logic here? Anyone experienced similar symptoms before? Any advice on replacing the gasket if that is the likely culprit, all the nuts/studs/bolts/whatever they are look pretty well rusted?

Would appreciate any input on the above. Cheers in advance,
Adam

[Othen]

Good morn,

You may be over thinking this one a bit.

If an exhaust gasket is leaking you will be able to feel it - if there isn't enough access to get your hand in around the where the manifold meets the head then use a little streamer of tissue paper on the end of a stick (maybe disable the fan it it is too breezy). You can do the same to check the joint where the manifold meets the downpipe. Check along the manifold casting as well - sometimes they crack. The gas in the exhaust is hot and under a lot of pressure as it exits the head, so even a small leak will show up straight away with this old fashioned method. This is an older (B23) motor - but you will get the idea:



If the gaskets are leaking then changing them isn't hard. Loosen the exhaust pipe mounting to give some slack and undo the 8 nuts. Some of the studs will probably come out at the same time so it isn't a bad idea to change them whilst you are at it. That will allow you sufficient clearance to pull the manifold out and remove the gaskets, clean up the surfaces and fit new ones.

It is probably a good idea to change the triangular gasket where the manifold meets the downpipe at the same time because you will probably have to loosen it to get enough clearance. This is a bit fiddly - the three nuts (15mm AF I think) are accessed from underneath with a really long socket extension. Remember to put some exhaust paste on that one.

The diagnosis takes 10 minutes, the repair (if you need it) an hour or two. You won't need any computers.

Good fortune,

Alan

PS. Before you do any of the above just check the 8 exhaust manifold nuts and the 3 that secure the downpipe are tight - I have known them to slacken off a little. Always do the simple and cheap things first.

[Steve 940]

Hi Adam,

I've got a 940 Turbo and a have had a hint of a blowing gasket at manifold for a while.

I traced it following some great threads on this forum, used a bit of Fairy Liquid in water sprayed around manifold.

As it gets so hot with the Turbo, and access is not great I used my workshop vac with hose plugged into the 'blow' outlet and taped into rear of exhaust pipe, leaving a bit of a gap.

This allows you to do check with the engine cold and not running, mine had two leaks, these seal up once warm though.

I did get all the bits including new genuine Volvo studs and nuts, not cheap. But on looking at in detail the Turbo needs an oil feed pipe that apparently can be tricky to get sealing right. Hence I've left it till I need to do something else in that area.

Good luck, and hopefully yours will be easier to access.

Cheers
Steve

[Othen]

Originally Posted by Steve 940

Hi Adam,

I've got a 940 Turbo and a have had a hint of a blowing gasket at manifold for a while.

I traced it following some great threads on this forum, used a bit of Fairy Liquid in water sprayed around manifold.

As it gets so hot with the Turbo, and access is not great I used my workshop vac with hose plugged into the 'blow' outlet and taped into rear of exhaust pipe, leaving a bit of a gap.

This allows you to do check with the engine cold and not running, mine had two leaks, these seal up once warm though.

I did get all the bits including new genuine Volvo studs and nuts, not cheap. But on looking at in detail the Turbo needs an oil feed pipe that apparently can be tricky to get sealing right. Hence I've left it till I need to do something else in that area.

Good luck, and hopefully yours will be easier to access.

Cheers
Steve

That is a cunning trick with the vacuum cleaner Steve.

Being a tightwad I don't bother with genuine Volvo studs and nuts, I bought (cheap as chips) generic M8 nuts and studs. They work fine. Each to their own though.

Alan