I’ve been working to patch up the exhaust on my 2009 XC90 with 3.2 engine. I live in a city where very heavy road salt is used, and it has taken a toll on my suspension and exhaust. I love the car, and don’t really see anything else on the market that would meet my needs as well. I am trying to keep it running as long as possible without spending too much on it.
Some of the work has involved patching leaks and replacing a rusty hanger on the downstream catalytic converter, during which I managed to break a couple of the screws holding the downstream cat pipes to the upstream manifold/cat assemblies.
I tried drilling out one of the screws (now stuck in the lower threaded flange of the manifold) without removing the manifold, but the positioning is so awkward I just ended up breaking the drill bit which also ended up going off-center and enlarging the hole. Here’s a photo showing how the original hole was enlarged by the adjacent of-center hole. The threaded rod is a plug of mild steel I machined and later welded into the hole for rethreading (after eventually removing the manifold).
I would have just removed the manifold in the first place, but this requires removing the upper heat shield that is bolted onto the engine block as well as a hanger on each manifold. The screws holding this shield onto the manifold were both severely seized and also rounded over (either from rust or someone’s past attempts to remove).
So I ended up doing what I should have done in the beginning – dealing with the whole heat shield/manifold mess by removing everything. The original heat shield was pretty rusty in spots, so I ended up just cutting it off from around the manifold hangers and unbolting from the engine block. I found that a swivel headed box-end wrench worked great for the screws holding the shield to the engine block, and these were not hard to remove after some fumbling.
I was also lucky that the manifold screws were fairly easy to remove from the engine block using a standard ratchet with a 3″ extension (the screw head is 10mm). So getting the manifold/cat assemblies off of the engine block was pretty easy once I got the heat shield off.
I found that the trickier part was pulling the manifold assemblies out of the engine bay, as the space between the engine and the rear bulkhead is pretty tight (at least in relation to the somewhat bulky manifolds). After a lot of fumbling about, I did end up getting both sides of the manifold out, but honestly can’t even remember how I did it.
I’ve addressed the broken screws and tap, as well as the seized heat shield screws, and am ready to re-install both sides of the manifold. Before fumbling around blindly again, I thought I’d ask if anyone has any tips on the best orientation or approach to go about this.
For example, it looks like removing the oil separator (PCV) might help give more space, but I’m not 100% sure that’s necessary. I have an engine lift, but was able to get the manifolds out without moving the engine.
If anyone has tips on how go get the manifolds back into position to bolt them on, I’d be very grateful and will put up a video on YouTube (my searches thus far haven’t turned up anything similar).
I’m glad I ended up dealing with the rusted on heat shield and removal of the manifold, but the moral here is that it is usually better to do whatever dismantling is required to properly address an issue so that it doesn’t become a bigger issue.