- 6 Min Read
- By: Tim Wong
How to Install a Full Exhaust System on a Volvo 940
I’m starting to think there are either little gremlins at work inside my car, or it's got a character of its own. A couple weeks ago, I announced to my editors that I may be running out of things to work on as my car has been running beautifully. Hand on heart, there were no immediate issues on my car that needed work. Well, I guess the Volvo heard me and proceeded to spring a leak in its exhaust. I initially tried to patch it up with some exhaust sealer, but it didn’t work. At all. Using my shop vac method of exhaust leak diagnoses, I could see leaks pretty much at every single connection. Bubbles from my soap spray were forming between the block to exhaust header, header pipe to exhaust header, the header pipe itself, catalytic converter to header pipe joint, around the O2 sensor on the catalytic converter and from the seams of the center exhaust. I had already welded up various parts of the exhaust twice before, but there is a point that patches and welds just won’t do. If my car has character, it must be a needy one.
I ordered all my parts from FCP for this job. Interestingly, my car, despite being a 940 GLE, has the same exhaust as a 940 Turbo model. I found this out the hard way as I bought the axle pipe meant for non-turbo cars. On the other hand, every other component fit fine. Whether my car came equipped with this exhaust from the factory, I have no idea. However, my final purchase included:
- Exhaust Muffer Center - (Starla 3536026)
- Catalytic Converter – NOT CA Legal - (Bosal 099-941)
- Exhaust Header Pipe - (Starla 855-473)
- Exhaust Manifold Gasket Set - (Proparts 1378852)
- Exhaust Pipe Flange Gasket - Header Pipe to Manifold - (3531326)
- Exhaust Stud – Manifold to Header Pipe - (Bosal 258-953)
- Exhaust Flange Nut Header Pipe - (CRP 977211)
- Volvo Exhaust bolt kit – Header to converter - (BOLTKIT1)
- Exhaust pipe axle - (Starla 738-025) Qty x1
- 55-58mm Exhaust Clamp - (CRP 975260) Qty x2
- 62mm Exhaust Clamp (CRP 975262) Qty x1
- Front and Rear Exhaust hanger kit (OEM Volvo)
Step 1: Inspect Your Parts
When you receive your parts, always make sure that what you ordered is indeed what you meant to order. Its not that I don't have any faith in FCP to pack the proper parts, but you may find that you either forgot to order something, or you simply ordered the wrong part. That's the great thing about FCP. If something's not quite as it should be, they'll do everything they need to make it right. In my case, after I recieved my parts, everything was in order apart from the aforementioned axle pipe. I also opted to paint my exhaust with high temperature paint to prolong its life.
Starla exhaust components and Bosal Catalytic converter
Step 2: Loosen Exhaust Manifold Nuts
As you’ll notice, I needed to remove everything in the exhaust system including the manifold all the way back to the tailpipe. This involves…removing the manifold, probably one of the most feared tasks of a DIYer. A single broken manifold stud would spell a nightmare. I made sure to cover the bolts in PBblaster as much as I could and ran the car hot. While the manifold was still hot, I cracked the nuts loose one by one until every single bolt cracked loose. Once they were loose, I let the car cool and proceeded to remove other components of the exhaust.
B234F exhaust manifold removed
Step 3: Remove Oxygen Sensor
You’ll want to do this before you forget and your exhaust comes tumbling down and severing your sensor wire. I don't know this firsthand, but I am sure someone reading this does. Make sure you get yourself a proper O2 sensor socket as these will always be very tight. Without a proper socket, you can very easily round off your $100 sensor and spend the rest of your day wondering why you didn’t pick up the proper tool. In my case, I cracked the sensor loose while the exhaust was still hot. This in combination with my breaker bar and socket did the trick.
O2 sensor socket
Step 4: Remove Rear Exhaust Components
For younger exhausts, you can usually undo the clamps and slide your pipes apart, taking out your exhaust in sections. However, if your exhaust was installed before the millennium like mine it’s going to take more than elbow grease to remove. I opted to cut apart the exhaust with an exhaust-specific pipe cutter. This was the essentially the only option available to me. I sliced the exhaust into three sections near the normal connection points, with the exception of the header pipe, where I cut it close to the junction of the double pipe in order to give me clearance on removal.
Did you notice that I didn’t mention removing the downpipe from the exhaust header? For whatever reason, I could not fit a socket onto the bolts due to clearance issues, hence cutting the header pipe where I did. Once your exhaust is free of itself, remove the exhaust from their rubber isolators. Simply spray a bit of WD-40 into the gaps of the rubber and wiggle them around. These should slide out easily and allow you to remove the rusty pipes.
I also needed to save the rearmost muffler so I had to hack and drill away a tubular piece from the inside. In hindsight, I should have simply replaced the exhaust piece.
Rear muffler removal
Step 5: Remove Exhaust Manifold.
If you were lucky and you managed to loosen each manifold nut without breaking a stud, you can then remove all the nuts and lift your manifold out of your car. As I had my header pipe still attached, I needed to jack up my car near the maximum extension of my jack in order to wiggle it out from under the car. It must be noted that at no point was I underneath my car when it was in this precarious position.
Using an exhaust pipe cutter
Step 6: Clean and Check Your mating surfaces.
It goes without saying that every surface that a gasket will be sitting on should be clean. Use a wire wheel to remove as much rust or foreign material as possible, cleaning both sealing surfaces of your manifold, as well as making sure your header pipe connection is clean.
Secondly, ensure that your exhaust manifold sealing surface is flat. If it is not, either look for a replacement or get it machined. You can take your chances if it isn’t flat, but more often than not, it will start leaking sooner than you were hoping.
Step 7: Install your exhaust manifold and header pipe.
I was very happy to find that when reinstalling my header pipe, my socket could actually fit. That meant I didn’t need to worry about any clearance issues. Torque down your manifold in the proper order first, then connect your header pipe. It is key that the bolts are torqued in the proper order. Not doing so may cause leaks, and/or a potentially cracked manifold. In general, when dealing with a non-circular bolt pattern, you want to start tightening in the center and make your way to other bolts in a circular fashion. Using exhaust gasket sealer may be taboo for some, but as I had not planned on pouring too much money into my car, the sealer would take care of any small imperfections.
Manifold tightening order
Manifold installation. Note, this manifold was pre-installed due to clearance issues
Step 8: Connect your axle pipe to your center exhaust
In order to have enough clearance, you’ll want to connect your axle pipe to the center exhaust first, followed by other exhaust components.
Step 9: Hang your exhausts
It doesn’t matter which exhaust you hang up first, either the front or the rear first is fine. If your rubber isolators are difficult to slide on, just spray some wd-40 and they should slip on with little difficulty. Once both of your exhausts are lined up and the pipes are connected, tighten down your clamps. Contrary to logical thinking, I found that placing the clamps behind the slots on the outer pipe was essential to having a good seal.
Exhaust clamp location. Red exhaust sealer optional.
Step 10: Install your catalytic converter
This step might be a little tricky. You need to insert the catalytic converter into the center exhaust first, then raise it up to the header pipe, all the while keeping the round gasket in place. Some have suggested glueing the gasket into place, but I just used some gasket sealer to hold it in. There are usually two types of these gaskets available: one that is a deformable “mesh” type and another is a solid metal ring. In my experience, the solid metal ring will seal better and last longer. Be sure to tighten down your bolts to the proper torques. It is interesting to compare the significant size difference of the OEM catalyst to the Bosal catalyst. This is by no means a knock on the Bosal exhaust, but simply that OEM catalysts are designed to last much, much longer. The catalytic monolith inside the Bosal exhaust is at least 1/4 of the size of the OEM exhaust! If you're wondering, the gray stuff on the OEM exhaust is evidence of my failed attempts at leak fixes.
Old versus new catalyst. Bosal 099-941 pictured above, OEM below.
Step 11: Test for leaks
You’re almost there! Use whatever method you want and test for leaks. In 99% of cases, you will have to tighten down some clamps a bit more to stop the leaks. Don’t be too down on yourself when you see leaks all over the place. This is where I found out that the placement of the clamps is doubly important. I used my shop vac method while spraying each joint with a mixture of dishwashing soap and water to figure out where leaks were coming from.
Old versus new exhaust under car
Old versus new exhaust
If you’ve done everything correctly you will be motoring happily and quietly. If you’re like me, you may just find out that the ONE exhaust component you decided not to replace was in fact the offending culprit behind your exhaust install in the first place. In my case, there was no leaks in the offending rearmost muffler, but leaks everywhere else. It was a simple case of an exhaust which had rusted out from the inside and gave off a loud low-pitched noise that was impossible to identify while in the car and very difficult while outside. I had not thought much about it since it was only 2 years old, but sure enough 2 years was enough time for this exhaust to lose any muffling ability. For the record, this piece was not bought at FCP.
Tim is a Canadian from Windsor, with a knack for taking things apart, and sometimes putting them back together. He is a mechanical engineer by day and backyard mechanic by night. His mantra in life is to never break another bolt.