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The Idiot Guide to Precat Removal (Lotsa pics!)

89K views 226 replies 51 participants last post by  Stu UK 
#1 ·
From the first moment I got my Spyder, the first recommendation from everyone was "gut your cats!" But hey, that manifold is like right next to the motor! That's mechanical stuff! How am I supposed to deal with that? Well it turns out, that with the proper tools and a lot of time on your hands, its not that difficult.

Tools and consumables:

From my little precat removal experience, I've found out that the following is essential to an stress-free experience. I strongly suggest not starting this little project without:

1) deep and regular hex sockets (esp 12mm and 14mm)
2) breaker bar
3) PB Blaster
4) socket extension
5) lots of daylight

The essential tools that are required are:
1) ramps
2) 14mm, 12mm and 10mm sockets and ratchet
3) 2 gaskets from MrT (see diagram below)

Optional but nice to have are:
1) new studs
2) new bolts

Procedure:

Here's a diagram of the entire disassembly process. Please refer to this often:

For more diagrams, check here.

The first step is to put your car on ramps. Remember to have someone always spot you when using ramps. Also, keep your handbrake engaged for more control:


Access to the nuts that need to be removed from underneath the car is hindered by the rear diaper. You will have to remove this with a socket wrench. The screws are easily removed:


You can see the spots where screws need to be removed here:


It is also eases access if you remove the mid-diaper. The screws and poppets that need to be removed are highlighted:


From underneath the car, take a gander at the "3 Amigos", they will be your biggest challenge in this project. Refer back to the diagram to see where this is in. It's in Area 4 in the lower left hand side of the top diagram, near the 2 gaskets:


Use PB Blaster or similar product and drench the 3 Amigos. PB Blaster is cheap, frustration is expensive. Let sit for a couple of minutes (or hours, or days). Using a breaker bar, 12mm DEEP HEX SOCKET, and socket extension, pry the nuts loose by rotating counter clockwise.

It is essential that your socket is HEX shaped, as any other shape will easily make the nut lose it's thread due to the amount of force being applied.

You will need a DEEP SOCKET, as the studs extend past the end of the nut, making it difficult for your socket to have sufficient grip.

You will need a socket extension, as the location of the nut is very difficult to get at (maybe even impossible) without a socket extension.


After removing the 3 Amigos, you will need to remove 2 bolts that brace the manifold to the frame. They are directly to the top of the 3 bolts you just removed. Use PB Blaster to loosen. The left bolt is 14mm, the right is 12mm. There may not be room to use the breaker bar.


You're done with removing the nuts and bolts from underneath the car! Yay! Now to deal with the bolts on top. Pop the lid off the engine bay, and remove the rear strut bars. Instructions for this can be found here:

http://spyderchat.com/forums/index.php?sho...c=44014&hl=

Now to remove the top heat shield, which is held down by 4 bolts. Refer to the 1st diagram, this will be Area 2, top left hand side. You will see 2 bolts. Use PB Blaster to loosen the bolts, and use a 12mm socket and the breaker bar to remove the bolt by rotating counter clockwise:


Refer to Area 6 on the diagram. This is where the last 2 bolts that hold down the heat shield are. Use PB Blaster to loosen the bolts, then remove with a 12 mm socket and ratchet. There will not be enough room for a breaker bar, but the bolts will hopefully give before the bolts lose thread or snap



The heat shield is now loose, but the 02 sensors need to be remove first. Refer back to the diagram. This will be in Area 1. Left side:

Right side:


The 02 sensor harnesses can be disconnected easy, by pressing on the tab to unlock, then pull apart:


Now to remove the 02 sensors. You will need an 02 sensor socket. This is looks like an ordinary socket, with a slit on the side for the sensor wire to pass through:


Soak the 02 sensor in PB Blaster. Wait a couple of minutes. Place the 02 socket on the 02 sensor, passing the wire through the slit, like so:


You can now remove the 02 sensor using a ratchet, or a breaker bar if space allows:


Here's what it looks like removed:


After taking off the other 02 sensor, you're now free to take off the top heat shield:


You've now exposed the manifold! See Area 3 in the diagram on top for reference. There are 5 12mm bolts that connect the manifold to the engine. Use PB Blaster to loosen the bolts. Use 12mm DEEP SOCKETS and the breaker bar to remove the 5 bolts.


Pull out the manifold, and remove the heat shields from it. You're halfway there! Now to re-assemble everything!

 
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#2 ·
At this particular step, your options vary. You can:

1) Decat your stock manifold (SE has a good thread with pictures here: http://spyderchat.com/forums/index.php?showtopic=16029)

2) Install a pre-gutted manifold purchased from someone else

3) Install a header

Whichever option you select, the next steps will generally be the same.

So here's your engine bay. Lots of space without the manifold:


Install the gasket that mounts to the engine. Refer to Area 3 in the diagram. Easy:


Install the 2 smaller gaskets that mount near the 3 amigos. Refer to Area 4 in the diagram. You may have to shape the gaskets so that the fit around the 2 openings snugly:



Mount the gutted manifold / header on the 5 studs:


Prep all areas that will be bolted down by spraying with WD40 or similar product, then install the nuts and tighten by hand:


Underneath the car, line up the bottom of the manifold/header, and put on the 3 amigos and tighten by hand:



Install the bolts that brace the manifold against the frame. Remember, 14mm on the left, 12mm on the right. Tighten by hand:



At this point the manifold should be aligned properly, with all nuts and bolts tightened by hand.

Use the ratchet, socket extender and 12mm deep sockets to tighten the 3 nuts at the bottom of the manifold. Refer to Area 4 in the diagram:


Use the ratchet and 12mm and 14mm sockets to tighten the bolts that hold the manifold to the frame, directly above the nuts you just tightened:


Bottom part is done for now!

Back on top, tighten the 5 nuts at the top of the manifold by using the ratchet and 12mm sockets. See area 3 in the diagram:


Mount the top heat shield:


Install and tighten the top 2 bolts using a ratchet and 12mm sockets:


Install and tighten the 2 lower bolts using a ratchet and 12mm sockets:


Install and hand-tighten the 02 sensors:


Tighten the 02 sensors using the 02 sensor socket and the ratchet:


Reconnect the 02 sensor harnesses:


Finally, reinstall the rear diapers, reinstall the rear strut braces, take the car off the ramps, go for a drive, and sleep at peace for ever after not worrying about pre cats anymore!


Driving impressions
Well, I never expected any benefit from decatting, but there actually was! The engine seems to breathe more freely, and there is a slight increase in bass from the exhaust. Not a bad thing at all!
 
#3 ·
This is a quote from an old post of mine re precats:

<div class='quotetop'>QUOTE </div>
I started the job at around 11am this morning, although I'd been contemplating doing it for a few weeks. I'd ordered the 2 round gaskets a couple weeks ago from an online parts company whose name I can't remember and whom I found out about from an SC post. I bought an O2 socket yesterday. So, today was the day.

The heat shields came off and the sensors came out with no problems. I went in to the house to feed the bird, and by 1130 I was staring at the 5 manifold nuts.

I had no deep sockets, so I had to fit the socket to the nut, then push the socket wrench only about half way into the socket. This worked, but sockets were falling on the ground all day long.

The manifold nuts came loose surprisingly easily; 3 came off as nuts and the other two came out still attached to the studs. Not a problem. I then loosened the bottom left manifold bracket at the block.

Next, I jacked and jack-standed the car, took off the bottom covers, and contemplated the dreaded 3 maincat-to-manifold nuts. I hadn't used any Liquid Wrench on anything, but oh, well.

Using the above mentioned half inserted socket handle technique on the nuts, I attempted to turn the nuts with a socket wrench and a ten inch extender. Needless to say, there was no way those nuts were going to move. BUT...I had a secret weapon!

I attacked them with socket, extender, and this time my trusty air impact wrench. Well. One burst, and the nut came flying off! It came off so quickly and easily, I first thought I'd snapped it off the stud. The other two came off just as easily. It should be noted, however, that the nuts were not rusted. The previous owner of the car must have had it garaged all the time.

The one bolt I DID have trouble with was the right manifold bracket bolt. I couldn't get that out to save my soul. I ended up taking out the bolt on the manifold itself, and leaving the bracket on the block. The manifold was now free.

It lifted right out, and I set about breaking up the cat material with a large screwdriver and a hammer. BTW, the cats looked perfect. So good, in fact, that I was tempted (for about a nanosecond!) to leave them and put it all back together.

They broke up easily, and the fiberglass lining came out easily with a long surgical clamp to grasp the pieces. Then a few minutes blowing it all clean with an air jet.

Putting it all back together was pretty uneventful. I followed the advice of several members and mounted the manifold loosely until both bottom brackets were lined up and threaded in. Then everything was tightened at tight as I could make it. I didn't use the impact wrench for tightening. Then the heat shields back on, the bottom plastic back on, the car lowered back to the ground, and the O2 sensors put back in.

It was now 4pm.

I nervously started it up, and voila, no problems, no cels, nothing but sweet running car. I drove it around until it was fully warmed up, and no issues whatsoever.[/b]
You need to get under the car to get the manifold separated from the main cat. It's held by 3 bolts, which may or may not give you grief when you try to remove them. That's mostly where the bolt loosener comes in. The bolts holding the manifold to the engine aren't that bad. Most people talk about leaving the loosener on overnight. As I said above, I didn't use any. Your call.

There are three gaskets involved. One is the gasket between the manifold and the engine. This is a thin copper sheet which, at least in my case, could be reused. I recently helped a SC member gut his precats at my house, and his gasket was fine, too. The other two gaskets are of the press fit type and cannot be reused. They're round and about the diameter of a coffee mug. They go between the bottom of the manifold and the main cat. They fit into a couple of recesses in the main cat flange and have to be replaced. You can buy them from MRT for big bucks or order them online for about three bucks apiece. Wait until you get them before starting.

As you can read from my post, I didn't have deep sockets, and it was doable, but a pain, without them. I since obtained some, and life is much better. I think the sizes you need are 10mm, 12mm, and I think a 14mm for the three bolts holding on the main cat. Look around in the posts on precats, I'm sure you'll find the sizes.

The two o2 sensors on the heat shields have to come out. First, carefully unclip the wire harness so the sensor is free, then use an o2 sensor socket to get the sensor out of the manifold. The o2 socket looks just like a deep socket except that it has an eighth inch or so slice, or gap, running the whole length of it. This is so the socket can be slid over the sensor without damaging the wires. The wires DO NOT come off the top of the sensor. Don't try to get them off or you'll be buying new ones.

As to getting the bolts/studs out of the manifold you're planning on using, I'll let others expound on that. If you have no tools, that's going to be a problem. Worst case, take the manifold to a shop and ask them to do it. Then buy some new studs. Not a major deal, really. A worse deal would be if the studs broke off in the engine. Hopefully that won't happen. Just work carefully.

The whole process takes almost as long to explain as it does to do it. It's really not that difficult. If you like, PM me and we can talk about it more. I'd be happy to help talk you through it when you actually begin the work.
 
#4 ·
OK, if I understand the procedure correctly:

Tools:
- lift, jacks, or ramp
- O2 Sensor socket
- ratchet, breaker bar, various regular and deep sockets
- WD 40, bolt loosener, or power impact wrench

Consumables:
-2 sets of gaskets (total of 3)

Procedure:



1) Remove O2 sensor (x2) with O2 Sensor Socket
2) Remove bolts (X2) from top heat shield
3) Remove engine to precat bolt (X5)
4) From underneath, remove the rear under-plastics and remove precat to main cat bolt (X3)

Extract the precat

5) Remove top heat insulator bolt (X2)
6) Remove side heat insulator bolt (X2)

Gut the precats / replace with manifold

7) reverse steps 5 & 6
8) reverse step 3, installing new gasket
9) reverse step 4, installing new gasket
10) reverse step 2
11) reverse step 1
 
#5 ·
<div class='quotetop'>QUOTE </div>
The two o2 sensors on the heat shields have to come out. First, carefully unclip the wire harness so the sensor is free, then use an o2 sensor socket to get the sensor out of the manifold.[/b]
I needed to perform a visual inspection of the manifold yesterday, so I pulled the O2s and heatshield. I tell ya, when you're doing this the second time around, it's a whole lot easier. I noticed that there's a slight difference between the two O2 sensor leads. The plug on the right is easy to separate while attached to the bracket that holds it, and you only need to detach the left sensor harness from its bracket. When you're actually doing this, you'll see why. You can fit the tips of needle nose pliers and unseat the left sensor harness for separation, but the one on the right is reversed, with the part you'd use the pliers on under the bracket so you can't see it. Turns out it's easy to just unplug it and leave the other half attached to the bracket.

Deep sockets are a very good idea for the manifold nuts and your wrench should have a swivel in the neck, you got some weird angles - an extender is good to have, too.

I recommend bolt loosener on all these things, and also, for reinstallation, have some Loc-Tite Anti-Seize compound for dressing the various bolts.

As you start along, you may be setting nuts and bolts and things beside the car and on your workbench. NOT CLEAR. Instead, use labeled ziplock bags for parts storage. If you do that, you will be glad, later.

You raise the back end primarily to get at...



Good luck with those clowns. There are many ways of releasing seized bolts and nuts, and many ways of recovering from stripped and rounded and snapped versions of them. It's a good idea to have a shop nearby you can drive to in the event you need air tools or a cutting torch. So I advise you tackle the Amigos first. You get them off, and the two bolts that hold the lower manifold to the motor (12 and 14mm) and the rest of the job is downhill coasting. Good luck, Broudie. You're saving the car; don't give up until it's done.
 
#6 ·
You will most likely need a 14mm for the header nuts.The studs are long so your regualer socket won't reach them.

Good luck with it.It is long overdue,hopefully they still look perfect.We will help you through it,just pm or post it up.
 
#8 ·
Toyota


You can reuse the manifold->head gasket, but you will definitely have to get new ring gaskets (manifold->downpipe). They're inexpensive in the UK ($14 ea. I think), so should be about the same over there.
 
#9 ·
<div class='quotetop'>QUOTE (aaronjb @ Jul 8 2007, 05:48 PM) <{POST_SNAPBACK}></div>
Toyota


You can reuse the manifold->head gasket, but you will definitely have to get new ring gaskets (manifold->downpipe). They're inexpensive in the UK ($14 ea. I think), so should be about the same over there.[/b]
If you break the studs like me you can buy them at toyota dealership too. ALso you may experience a ticking noise after the install, which means you have a leak. It is very annoying.
 
#10 ·
<div class='quotetop'>QUOTE (groovespacer @ Jul 8 2007, 05:54 PM) <{POST_SNAPBACK}></div>
..If you break the studs like me you can buy them at toyota dealership too. ALso you may experience a ticking noise after the install, which means you have a leak. It is very annoying.[/b]
More concerned about how I pull off the broken studs! The decatted manifold I'm installing still has them on! Right now its soaking in WD40 but I'm not sure I can pull them off with a vise grip..
 
#11 ·
I'd try Toyota before going online for the gaskets. My dealer actually had all 3 gaskets ready to go. IIRC it was 16 for the manifold gasket, and 7 a piece for the smaller press-fits. As for identifying them, I'd just have the guy pull up that diagram you have posted and point out the ones you need. I tried asking for them by name, and after the words "MR2 spyder", the guys face just went blank.
 
#12 ·
<div class='quotetop'>QUOTE (broudie @ Jul 8 2007, 07:19 PM) <{POST_SNAPBACK}></div>
<div class='quotetop'>QUOTE (groovespacer @ Jul 8 2007, 05:54 PM) <{POST_SNAPBACK}>
..If you break the studs like me you can buy them at toyota dealership too. ALso you may experience a ticking noise after the install, which means you have a leak. It is very annoying.[/b]
More concerned about how I pull off the broken studs! The decatted manifold I'm installing still has them on! Right now its soaking in WD40 but I'm not sure I can pull them off with a vise grip..
[/b][/quote]
Just try the vice grips,they should do the job.Other options would be heat or drilling.I don't think you wanna drill and tap though.Why did you buy a messed up header?
 
#13 ·
<div class='quotetop'>QUOTE (spydercam @ Jul 8 2007, 06:26 PM) <{POST_SNAPBACK}></div>
<div class='quotetop'>QUOTE (broudie @ Jul 8 2007, 07:19 PM) <{POST_SNAPBACK}>
<div class='quotetop'>QUOTE (groovespacer @ Jul 8 2007, 05:54 PM) <{POST_SNAPBACK}>
..If you break the studs like me you can buy them at toyota dealership too. ALso you may experience a ticking noise after the install, which means you have a leak. It is very annoying.[/b]
More concerned about how I pull off the broken studs! The decatted manifold I'm installing still has them on! Right now its soaking in WD40 but I'm not sure I can pull them off with a vise grip..
[/b][/quote]
Just try the vice grips,they should do the job.Other options would be heat or drilling.I don't think you wanna drill and tap though.Why did you buy a messed up header?

[/b][/quote]
I will leave that SC member's name anonymous


OK, vise grips + WD40 did not work, the threads are just peeling away under the vise. What is my next option?

EDIT: Alright, ONE of the 2 broken bolts I was able to pull off using the vise, but damn! I was putting in more than 150lbs of force on it I swear. The other one is a bit more challenging, as the cut bolt is pretty short. I'll put some more more WD40 on it before trying again tonight. I effin' hope that pulling those lose will be a lot easier.
 
#14 ·
<div class='quotetop'>QUOTE (broudie @ Jul 8 2007, 07:39 PM) <{POST_SNAPBACK}></div>
<div class='quotetop'>QUOTE (spydercam @ Jul 8 2007, 06:26 PM) <{POST_SNAPBACK}>
<div class='quotetop'>QUOTE (broudie @ Jul 8 2007, 07:19 PM) <{POST_SNAPBACK}>
<div class='quotetop'>QUOTE (groovespacer @ Jul 8 2007, 05:54 PM) <{POST_SNAPBACK}>
..If you break the studs like me you can buy them at toyota dealership too. ALso you may experience a ticking noise after the install, which means you have a leak. It is very annoying.[/b]
More concerned about how I pull off the broken studs! The decatted manifold I'm installing still has them on! Right now its soaking in WD40 but I'm not sure I can pull them off with a vise grip..
[/b][/quote]
Just try the vice grips,they should do the job.Other options would be heat or drilling.I don't think you wanna drill and tap though.Why did you buy a messed up header?

[/b][/quote]
I will leave that SC member's name anonymous


OK, vise grips + WD40 did not work, the threads are just peeling away under the vise. What is my next option?

EDIT: Alright, ONE of the 2 broken bolts I was able to pull off using the vise, but damn! I was putting in more than 150lbs of force on it I swear. The other one is a bit more challenging, as the cut bolt is pretty short. I'll put some more more WD40 on it before trying again tonight. I effin' hope that pulling those lose will be a lot easier.
[/b][/quote]
Forget wd-40 get you some pb blaster.
Also get your vice grips on real tight and get a hammer after them.Just lock them on as good and as tight as you can then beat it with the hammer till you get it loose if turning it doesn't work.

Good luck.
 
#16 ·
<div class='quotetop'>QUOTE (spydercam @ Jul 9 2007, 05:59 AM) <{POST_SNAPBACK}></div>
<div class='quotetop'>QUOTE (broudie @ Jul 8 2007, 07:39 PM) <{POST_SNAPBACK}>
<div class='quotetop'>QUOTE (spydercam @ Jul 8 2007, 06:26 PM) <{POST_SNAPBACK}>
<div class='quotetop'>QUOTE (broudie @ Jul 8 2007, 07:19 PM) <{POST_SNAPBACK}>
<div class='quotetop'>QUOTE (groovespacer @ Jul 8 2007, 05:54 PM) <{POST_SNAPBACK}>
..If you break the studs like me you can buy them at toyota dealership too. ALso you may experience a ticking noise after the install, which means you have a leak. It is very annoying.[/b]
More concerned about how I pull off the broken studs! The decatted manifold I'm installing still has them on! Right now its soaking in WD40 but I'm not sure I can pull them off with a vise grip..
[/b][/quote]
Just try the vice grips,they should do the job.Other options would be heat or drilling.I don't think you wanna drill and tap though.Why did you buy a messed up header?

[/b][/quote]
I will leave that SC member's name anonymous


OK, vise grips + WD40 did not work, the threads are just peeling away under the vise. What is my next option?

EDIT: Alright, ONE of the 2 broken bolts I was able to pull off using the vise, but damn! I was putting in more than 150lbs of force on it I swear. The other one is a bit more challenging, as the cut bolt is pretty short. I'll put some more more WD40 on it before trying again tonight. I effin' hope that pulling those lose will be a lot easier.
[/b][/quote]
Forget wd-40 get you some pb blaster.
Also get your vice grips on real tight and get a hammer after them.Just lock them on as good and as tight as you can then beat it with the hammer till you get it loose if turning it doesn't work.

Good luck.


[/b][/quote]

+1 on the pb blaster. WD-40 is not the right stuff for removing rusted fasteners. Soak it good with PB Blaster, snap those vice grips on tight and give the stud a tap tighter before trying to loosen it.
 
#17 ·
Broudie this is going to be a good write-up with the labeled diagram in it. You are working and writing at the super-noob level which will help a few people.

Some people, including me, swear by a penetrating oil called Kroil (www.kanolabs.com). Supposedly you can only get it mail order but my local True Value hardware store had it. I've never used PB Blaster so I can't say Kroil is better, but some people say that.
 
#18 ·
Another vote for PB. It's always worked well for me. Check out it's abilities by spraying it on a styrofoam cup. I don't know what that supposedly proves, but it's cool.
 
#20 ·
At the last gutting meet in the UK we ended up with two manifolds containing snapped studs..

In the end we had to get the studs taken out by an engineering shop who ended up having to spark erode them out of the manifold..
 
#21 ·
This final snapped bolt is killing me! I've already scraped off maybe 1/8th inch off it from using the vise grip. Its not budging, and my vise grip is starting to lose some teeth!

Next option?
 
#22 ·
Pick header up with both hands.

Carry to your other car.

Put header in trunk.

Drive to that shop you lined up before starting this job.

Ask nice gentleman standing by the rack if he can get this off.
- pro tip: tell 'em, "I've done everything I can and there's no way this sucker's coming off!"

Watch mechanic pop the bolt out in 3 seconds.

Offer to pay for this marvelous assistance.

Listen to shop people laugh as they turn around and go back to whatever they were working on.
 
#23 ·
<div class='quotetop'>QUOTE (broudie @ Jul 9 2007, 01:04 PM) <{POST_SNAPBACK}></div>
This final snapped bolt is killing me! I've already scraped off maybe 1/8th inch off it from using the vise grip. Its not budging, and my vise grip is starting to lose some teeth!

Next option?[/b]
I would try some heat next. Use a propane torch to heat the manifold around the offending stud and try rocking the stud both directions to crack it loose. If this doesn't work you're probably going to have to take it to a shop. Look for a machine shop. This won't be a big job for them and shouldn't cost much.
 
#24 ·
<div class='quotetop'>QUOTE (southerneditor @ Jul 9 2007, 05:45 PM) <{POST_SNAPBACK}></div>
Pick header up with both hands.

Carry to your other car.

Put header in trunk.

Drive to that shop you lined up before starting this job.

Ask nice gentleman standing by the rack if he can get this off.
- pro tip: tell 'em, "I've done everything I can and there's no way this sucker's coming off!"

Watch mechanic pop the bolt out in 3 seconds.

Offer to pay for this marvelous assistance.

Listen to shop people laugh as they turn around and go back to whatever they were working on.[/b]
That might work in a perfect world but in my part of town they would say,"That will be 70 bucks."


I need to move to Florida.
 
#25 ·
<div class='quotetop'>QUOTE </div>
That might work in a perfect world but in my part of town they would say,"That will be 70 bucks."[/b]
The right kind of place will one that does this sort of thing all the time. Like, say, a muffler shop. The trick is making friends with them first, and then being very courteous. This has worked for me all over the states, both coasts, the deep south... it's all in how you ask.
 
#26 ·
<div class='quotetop'>QUOTE (southerneditor @ Jul 9 2007, 07:41 PM) <{POST_SNAPBACK}></div>
<div class='quotetop'>QUOTE
That might work in a perfect world but in my part of town they would say,"That will be 70 bucks."[/b]
The right kind of place will one that does this sort of thing all the time. Like, say, a muffler shop. The trick is making friends with them first, and then being very courteous. This has worked for me all over the states, both coasts, the deep south... it's all in how you ask.
[/b][/quote]
I must work on this technique you speak of se. Thanks for the advice.
 
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