355 Header Removal

Just as an update, the check engine light was due to the idiot who did the work on the car. I read the diagnostic codes and the car was throwing a P0112, which is low voltage on the intake air temperature sensor. Turns out that can happen if it’s not plugged in at all. I reconnected it and cleared the code. So far, so good. Now I just have to get the exhaust bypass valve working correctly and the car will be just about 100%. I’ve checked for vacuum leaks on most of the system and all seems to be fine. Next step is to check the solenoid and the signal to the solenoid from the ECU. The valve itself seems to work great, but it doesn’t open when it should. I wired the valve open yesterday and heard the car sing for the first time. What a sound!

 

Yep, I know. I already unwired it, so it is closed again. I just wanted to make sure I was correct in my assessment that the valve was not opening when it is supposed to.

Regarding the valve, maybe I’ll make a separate thread on it. I’ve read through all of the previous threads I can find, but I’m still not having much luck diagnosing the problem.

I’ve applied vacuum to the valve directly and it functions. Do we know how much vacuum it should take to open it? I’ve checked the reservoir and all the lines leading from it to the bypass valve. No leaks found.

The bypass valve solenoid is showing 55ohms, so I believe it is good. The car is delivering 6v to the solenoid with the key turned to the on (car not running). In another thread, somebody got these exact measurements, but it was suggested the connector should be showing ~12v. Do we know what voltage should be sent to the solenoid under various conditions? The connector looked clean and free of corrosion.


I’m just about at a loss on the bypass valve and don’t want to run with it wired open for various reasons. I just want to get it working correctly. I think the next thing to check is that vacuum is actually being accumulated in the reservoir. That seems to be the final mechanical portion that I haven’t checked.


Any other thoughts on what I should be looking for? I’ve heard the valve open correctly at least one time, so the condition is apparently intermittent, but generally the valve never opens when it should. I am aware of the conditions that should trigger the valve to open and meet them frequently. I’ll take any and all suggestions. Thanks.

 

Any reason I couldn’t start the car and use a 9v battery to manually operate the solenoid valve and see if the bypass valve opens as it should? That would effectively diagnose the entire vacuum system and narrow things down to an electrical issue.

And a correction to my previous post. One side of the connector going to the solenoid shows 6v to ground and the other shows 12v to ground. When I test across the connector, I get 6v. I’m not very electrically savvy, so looking for any guidance at all.

 

Activated the solenoid using a 9v battery just to ensure the solenoid itself, the valve, and the vacuum system are all operating correctly, which they are. So now to chase down the wiring issue. The bundle of wires coming from the ECU doesn’t look fun to mess with, but I guess that’s where I’m at. Am I safe to assume that one wire at the solenoid should be grounded somewhere and the other (yellow/blue) just receives 12v when the valve is commanded open by the ECU? If that assumption is correct, do we know where the grounding point is? Odd that I get voltage on each pin of the connector.

 

I said I would post some photos of the process of replacing my headers, so here goes. As far as tools needed to get the job done, there weren’t many special tools needed. Just a variety of sockets (mostly the 13mm variety) some extensions, and universal joints. The most helpful tool I bought for the job was the swivel head socket wrench posted in the thread linked in one of the early replies to this thread.

Steps as I remember them off the top of my head and not in exact order:

1) Remove intake components (air boxes, and intake tubes leading to intake plenums). Be careful as you will have to unplug the MAF and IAT sensors to remove these.
2) Soak all of the nuts/bolts that hold the headers to the cats and y-pipe with some type of penetrating lube. I used WD-40 and had no issues. Disconnect headers from the cats and y-pipe.
3) Remove rear wheels and fender liners to gain access to the headers. I also had my car on a lift, which helped access some of the lower header nuts, though this is not necessary.
4) Soak all of the header nuts with penetrating lube for a while before you start trying to loosen them.
5) Remove air injection hose from headers. This should be done prior to loosening the header nuts because you want the headers secure to loosen what was a very tight connection for my air injection hoses.
6) At some point you will have to remove the radiator fans to give yourself enough room to slide the old headers out
7) On the right side, I did not remove the oil tank, but did need to remove the hose from the tank to the oil cooler. Mine happened to have been sealed with some kind of RTV instead of using the proper o-ring, so if you run into that, budget a solid hour to clean all of that up. Have a fresh replacement o-ring handy.
8) Begin carefully loosening the nuts on the headers. Some you can get from underneath, some from above. You’ll have to work out the easiest way for each nut as you go along. None were especially difficult, but I can confirm reports that the top forward-most nut on the right side of the vehicle was probably the most difficult
9) Once you have the all of the headers nuts removed, it’s just a matter of twisting and turning the headers to slide them out of the wheel wells. I initially tried this with the radiator fans in place and it did not appear possible, which is why I advise removing these fans prior to loosening the headers. The radiator fan on the left side of my car was easy to remove as it had captive bolts. The oil cooler fan did not have captive bolts, so it was quite a bit more tedious to remove, but doable with some patience.
10) Once you have the old header/s out, put on the new headers gaskets (it is obvious which side faces out because if you put them on backwards, they will partially block the exhaust ports) and loosely affix a couple of nuts to hold the headers in place.
11) Tighten down the nuts (I’d say to spec, but good luck getting a torque wrench on most of them). I tightened them starting in the center and working my way out. Not sure if that’s the optimal way, but it made sense in my head.
12) Re-attach the headers to the cats and y-pipe and reassemble the intake assembly and you’re done. Don’t forget to hook up both sensors on the intake or you will earn yourself a check engine light.

Hopefully this helps anybody else looking to do the job. All in all, it took me longer than it should have due to fitment issues that I believe are manufacturer related and I also spent time cleaning up parts of the engine and engine bay while I had easy access to them.

Also, if you have a 4-post lift like me, I used the lift to raise the car and then lowered the car onto jack stands to get the rear wheels off. So you can do this job with no lift or even with a 4-post lift. Anyway, here are a few assorted pictures I took of the process. I took less and less as I got deeper into the project because I just wanted to keep moving along. In some of the pictures, you can see all of the insulation that had been blown out of the right side header.



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