Has anyone tried to replace an exhaust manifold on a 5.0L before? Mine is leaking and I ordered one but am a little hesitant because of the rusty bolts and nuts.
I'm replying to this post for the benefit of anyone having a similar and more recent question. I just completed replacing both exhaust manifolds this evening.
Once I determined it was leaking exhaust and not valve chatter, I did some research: I had cast iron manifolds; the bolts were all very rusty, and it did not make financial sense to have a shop do the work or to use expensive dealer parts (which basically don't exist anymore). YouTube was a great resource, as usual.
If you don't have a place where you can work for two or three long days, preferably with a partner and on level ground, and with good lighting available, I would not recommend attempting this job. You also need a fair number of metric and SAE wrenches and sockets, and a torque wrench. A pneumatic impact tool also came in handy.
The passenger side was harder than the driver's side: The inside bolt of the exhaust flange connection to the manifold had to be cut off with a sawzall. This required cutting through the cast iron tail of the manifold to get to the bolt. This particular manifold had one connection for the EGR tube. The EGR tube added a level of complexity in that it was also seized on, and the tube collapsed on itself as we tried to get the compression nut off...so plan on replacing the EGR tube and get one with a layout that matches what you take out exactly.
Bolts/Studs: what a bizarre mess: Some were about 1.75" long 3/8-16 bolts; others were 2" long 3/8-16 studs; one other stud on each manifold was about 2.75" long because one part of each manifold has a thicker/deeper hole. None of the online sites said anything about this. Assume one or more studs will break. The bolts came out easier than the studs, and both long studs broke off at the nut. This is with the usual steps of penetrant and heat. We got by with a basic propane torch and the yellow MAPP gas canister. The heat shield nuts were also frozen on, but because we were replacing the unit we just pulled/cut off the heat shield to have better access to the studs/bolts.
Pulling off and setting aside the spark plug wires and removing the spark plugs made getting the manifolds out a little easier. Mark the wires and spark plug holes if the wires are not already marked: 1 through 4 front to back on the passenger side; 5 through 8 on the driver's side.
As multiple videos show, on the passenger side you need to remove the combination radiator reservoir/windshield washing reservoir, and a piece of equipment that I think has to do with cruise control, as well as the air box and pathway to the intake main valve. On the driver's side you need to remove the dipstick as well as separate the steering lower shaft. Follow all the directions and you should be good to go, including cleaning the old gasket off and scraping the surface clean and flat. Take extra care if your head is aluminum.
New studs: The holes in the head of my engine were 3/8-16, which did not seem to match a lot of "matches" on various automotive sites (usually calling for M8 or M10 studs). I called a Ford dealer and asked them to look up the spec based on my VIN. With that in hand, I decided to go with all studs rather than a mix of studs and bolts. The theory here is that if the holes had crud in them that I couldn't get fully out, the bolts might bottom out too early and you'd have to add washers or have a bolt that doesn't torque properly against the manifold, whereas you can drive a flange nut further down on a stud that might have bottomed out too early.
I got: 13 studs which had 3/8-16 on the inside section (3/4" length) and 3/8-24 on the outside section (about 1" length). Total stud length 2". I got these at the local hardware store. Supplier was Hillman. For the two thick manifold holes, I went with 2.75" studs, and for one additional stud that doubled as a bracket post for the dipstick, I went with 2.5". For flange nuts, I went with stainless 3/8-24. Would recommend you test every one of them before buying because some 3/8-16 were in the wrong bin and I had to go back and exchange them. I bought a standard 3/8-24 nut to assist with double-nutting the studs to seat them in the head, as well as some extra flange nuts to help with the piece that is the bracket for the dipstick.
I'm providing all these specs because I found this information very hard to find definitively online.
The heads were purchased online. Once they arrived, we had to clean up some rough machining that left a chunk of raised metal next to a couple holes. Those flange nuts need a flat surface to work properly. Also note: Unlike the stock manifolds, the new ones have M12-1.5 bolts, not 5/8" or whatever was stock, so don't try to re-use the old bolts and in any event the new exhaust flange bolts came with the manifolds.
Once the head is slipped into place, then the gasket is slipped onto the head side of it. Hand thread a couple studs to hold everything into place.
I bought some copper anti-seize as well as threadlocker red. Each stud was double-nutted, coated with threadlocker read on the 3/8-16 end, then hand threaded and seated with a 9/16" socket. This is after cleaning all the holes with WD40 and an air hose. If the threads are really bad, you may want to run a 3/8-16 tap into them carefully. We basically did one stud at a time. After the stud was seated, we lightly coated the stud with anti-seize, then ran a 3/8-24 flange nut down until it was just a little tight. We learned that sometimes one or two holes might be slightly off, so if you keep the initial nuts lightly tightened, it is easier to loosen them and adjust the manifold so all the studs will go in.
Once all the studs are lightly tightened, re-attach the EGR tube on the passenger side. You'll need a 1-1/16" spanner wrench for this task, and there isn't a lot of room to work with.
I believe the torque spec is in the range of 30 ft-lb on the exhaust flange nuts. For the longer studs, you could even go with a 3" stud...at 2.75" we found that the double nuts bottomed out before the stud itself bottomed out into the head, and a longer stud would have allowed us to avoid that.
For the stud that holds the dipstick, don't seat the dipstick bracket under the flange nut that pulls the manifold towards the head. Put on a separate flange nut backwards and up the stud a little bit to act as a platform for the bracket, then sandwich it with a flange nut going the normal direction.
Be sure to coat the steering wheel connection bolt with thread locker before reinstalling.
The dipstick hole was hard to find again and the area was quite sooty. If I were to do it over again, I would have thoroughly cleaned that area when the manifold was off.
On the driver's side, removing the heat shield on the back side of the A/C compressor was the only way that leftmost (forwardmost) stud could be removed and the new one installed.
We also took the opportunity to replace the spark plugs, since you have to take off the wheels and wheel liners to replace them anyway.
No more 'click-click-click-click' with a lack of power, and people turning to look at who has the bum engine.
