Is the exhaust expansion box necessary or can I bypass it by making separate exhaust pipe. A new expansion box is very expensive

There are usually two. Both on the exhaust system.
The first is on the manifold, where the exhaust pipe joins and the other is after the first expansion box or Catalytic Convertor.
There are pressure sensors as well at the Cat so check first.

This is pretty straight forward, you need to locate the exhaust manifold and follow it down to where it connect to the exhaust pipe, there three bolts on the joint and you take those out. Then see if you can separate the pipe from the manifold. If you cannot separate them then you need to get under the jeep and loosen the holders for the exhaust pipe. When you can separate the joint, take the old doughnut out and put in the new one. Make sure that you get it tight and that you tighten the bolts evenly. Don't over tighten one side.

Replacing a catalytic converter ranges from easy to moderate for most DIY mechanics. It is best to take off the entire exhaust system (not the exhaust manifold or headers) for a through inspection when doing this job as a bad catalytic converter is a sign that other parts of the exhaust system may be requiring replacement as well including the muffler(s) and tail pipe(s). Tenneco's Walker Muffler site has detailed schematics for both domestic and foreign cars. TRW Aftermarket may carry them too. (If you own a very expensive car; you plan on keeping for a long time , see about a stainless steel exhaust system... Borla, Remus, Supersprint, Bosal, and ANSA make many for foreign cars.) The other thing(s) to check and remove before taking the exhaust pipes off are the 1 or 2 Oxygen sensors... they will affect your gas mileage significantly. Unplug the wires to them and unscrew the front one and look at it. If it's filthy fouled replace it and the lower (if there are 2) one too... the information from both of them influences the car's ECM/ECU computer to adjust the air/fuel mixture.. (NGK, Beru, and Bosch make oxygen sensors for most cars.) Ensure you buy new exhaust pipe hangers and mounting bolts, if your hangers don't include them. Use Penetrating oil on a COLD exhaust system to help free up the bolts that join the lower part of the exhaust manifold to the first part of the exhaust system. Letting it sit overnight seems to work best. You may need a new gasket there so prepare and buy a new one to replace it. (When replacing, tight is good, too tight is bad as you may break off the stud or bolt.) IMPORTANT!!! Old catalytic converters need to be disposed of as hazardous waste as they contain several gridded wafers of electroplated platinum base metal. (Contact the new catalytic converter seller to see if they will take your old one or contact your city or county disposal office to see how to properly dispose of a used one.) Exhaust pipes typically fail where there are bends as the metal is stretched and thinner there... look for holes and rust. Typically, a ratchet set, rubber mallet and hacksaw may be required to cut a catalytic converter out and then crush the round inner sleeve remaining inside the exhaust pipes ends with a thin flat chisel, pulling it out of the "good" exhaust pipes using locking pliers (a.k.a. Vise Grips tm). (Alternatively, a rubber mallet may be used to strike the catalytic converter to break it loose from the exhaust pipe ends... DO NOT DO THIS if the catalytic converter is in the disintegration stage. Do Not use the mallet on the exhaust pipes as they will bend!) Use crocus cloth or sand paper to smooth the inside of the exhaust pipe connections and ensure by trial off the car that the new catalytic converter goes in the pipe ends easily before mounting the separate pieces on the car... terrible to learn it won't go in, due to carbon soot or rust when you're on your back underneath!

1) Take it to a muffler shop unless you are a good welder.
2) Procure the new exhaust pipe material.
3) Make the necessary bends in the new pipe to correspond with the layout of the old pipe with a hydraulic tubing bender.
4) Use a band saw to cut the new pipe to lengths using the old pipe as a template.
5) Weld the pieces to form the crossover.
6) Using a cutting torch, cut both exhaust pipes to the length you made the crossover.
7) Weld in the new crossover you just made.
8) If you can't weld with a torch, have no access to a tubing bender and have no way to get the correct exhaust pipe material....take the car to a muffler shop.

Thermostat? engine cooling?
2 engines, here, LYA adn LY7.
nobody here posts engine, why do that?
so ill post only for 1.
the LA1
here are the steps.
NO FSM Sux huh? nor an alldata.com account, why not that? 15 bucks?


STAT out.
Remove the air cleaner and duct assembly. Refer to Air Cleaner Assembly Replacement in Engine Controls - 3.4L.

Drain the coolant until the coolant level is below the thermostat. Refer to Cooling System Draining and Filling (Refer To List 1) .

Remove the crossover exhaust pipe. Refer to Exhaust Crossover Pipe Replacement (Refer To List 2) in Engine Exhaust.

Remove the radiator hose from the thermostat housing.

Remove the thermostat housing bolts and clean any sealer from the bolt threads.

Remove the thermostat housing and gasket.
remove STAT
next is crossover page.

Disconnect the battery ground (negative) cable. Refer to Battery Negative Cable Disconnection and Connection (Refer To List 1) in Engine Electrical.

Remove the throttle body air inlet duct.

Drain the coolant from the cooling system. Refer to Cooling System Draining and Filling (Refer To List 2) in Engine Cooling.

Remove the inlet radiator hose from the engine. Refer to Radiator Inlet Hose Replacement (Refer To List 3) in Engine Cooling.

Remove the thermostat bypass pipe. Refer to Thermostat Bypass Pipes Replacement in Engine Cooling.



Remove the exhaust crossover heat shield bolts.

Remove the exhaust crossover heat shield.

1. Remove the exhaust crossover pipe studs/nuts.
2. Remove the exhaust crossover pipe.

end , remove.

now the bypass pipe FWD cars SUCK

1. Disconnect the left engine mount strut from the engine.
2. Remove the heater hose from the bypass pipe.
3. Remove the thermostat bypass pipe to throttle body nut.
4. Use the J 38185 in order to remove the thermostat bypass pipe hose clamps (1,5).
5. Remove the thermostat bypass pipe to cylinder head nut (3).
6. Remove the thermostat bypass pipe bolt (4).
7. Remove the thermostat bypass pipe hose.
8. Remove the thermostat bypass pipe.

sigh.....
why not log in to alldata.com
read the page then ask ques tons that are not clear.
and next time post the engine type.
above is just 1 engine.

2.3L Engine

1. Disconnect the negative battery cable
2. Detach the oxygen sensor connector.
3. Properly drain the engine coolant into a suitable container. Remove the heater hose from the thermostat housing for more complete coolant drain.
4. Remove upper and lower exhaust manifold heat shields.
5. Remove the bolt that attaches the exhaust manifold brace to the manifold.
6. Break loose the manifold to exhaust pipe spring loaded bolts using a 13mm box wrench.
7. Raise and safely support the vehicle. NOTE: It is necessary to relieve the spring pressure from 1 bolt prior to removing the second bolt. If the spring pressure is not relieved, it will cause the exhaust pipe to twist and bind up the bolt as it is removed.
   
8. Remove the manifold to exhaust pipe bolts from the exhaust pipe flange as follows:
   1. Unscrew either bolt clockwise 4 turns.
   2. Remove the other bolt.
   3. Remove the first bolt.
9. Pull down and back on the exhaust pipe to disengage it from the exhaust manifold bolts.
10. Remove the radiator outlet pipe from the oil pan and transaxle. If equipped with a manual transaxle, remove the exhaust manifold brace. Leave the lower radiator hose attached and pull down on the outlet pipe to remove it from the water pump.
11. Carefully lower the vehicle.
12. Remove the exhaust manifold, seals and gaskets.
13. Loosen and reposition the rear engine mount and bracket for clearance, as required.
14. Remove the water pump mounting bolts and nuts. Remove the water pump and cover assembly, then separate the two pieces.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

{: ) You didn't mention your vehicle model. But anyway, the a/c expansion valve can be usually found at the engine compartment firewall, just a division away where it connects with the evaporator inside the dashboard. Just follow the trail of the two a/c pipes from the a/c compressor going towards the engine firewall, and there youl'll find a small rectangular block that serves as the junction point. That is the expansion valve.
The two pipes are mounted to the expansion by one or two bolts, depending on the model. Before you begin removing a/c components, make sure the surfaces especially the area of concern are cleaned, this is to prevent dirt or dust entering the a/c system. If possible, cover the pipes and openings. After removing the bolts, separate by pulling the two pipes aside. The expansion valve is mounted to the evaporator bracket, it's either a torx or an allen type bolts. You need to remove these bolts to separate the expansion valve from the evaporator bracket. Cover all openings of a/c lines to prevent contamination.
With the expansion valve removed, have time also to check the quality and color of the refrigerant oil. Check for possible contamination, flush the system if needed and reevaluate the condition of the compressor and condenser.
If everything seem to be fine, proceed with the new replacement of the expansion valve. It is also advisable not to reuse the old o-rings. Use new o-rings whenever possible.
Installation is just the reverse of the removal, so goodliuck.
I

Water pump is driven by timing chain idler and is mounted on the rear of the timing chain housing. Disconnect the neg. battery cable. Drain cooling system. Disconnect oxygen sensor connector.
Remove upper exhaust manifould heat sheild. Remove exhaust manifold brace. Remove lower exhaust manifold heat sheild. Loosen manifold to exhaust manifold spring loaded nuts. Remove radiator outlet pipe to water pump coverbolts. Disconnect exhaust pipe from manifold.
Pull down on the exhaust pipe to disconnect it from exhaust manifold bolts. Disconnect outlet pipe from oil pan and transaxle. If equipped with manual tranaxle, remove exhaust maifold brace. Leave lower radiator hose attached and pull down on radiator out look pipe to disengauge from water pump. Leave outlet pipe hanging.
Lower vehicle. Remove exhaustmanifold to cylinder head nuts. Remove exhaust manifold to cylinder head nuts. Remove manifould. Remove timing chain front cover. Remove timing chain tensioner. Remove bolts bolts securing water pump cover to cylinder block. Remove water pump to timing chain housing nuts. Remove water pump attaching nuts. Remove water pump and cover assembly. Separate componets as necessary.
WHEN INSTALLING WATER PUMP MAKE SURE YOU FOLLOW THE TIGHTENING SEQUENCES THAT AFFECT SEALING. My frist one I messed up and broke the pump so becarful.
Installation
If cover was separated from body during removal, join this componets with a new gasket and hand tighten bolts. Apply bearing grease to splines of water pump drive. Set body and assemble into position.
Install and hand tighten bolts securing cover to cylinder block. Install and hand tighten bolts securing cover to cylinder block. Installand hand tighten nuts securing body to timing chain housing. Lubracate outlet pipe "O" ring with antifreeze. (I use RTV) Connect outlet pipe. Install and hand tighten bolts. Tighten bolts and nuts to specification in the following sequence. I'll ad the torque spec. at the end but this is where if you tighten out of order something will break.
pump assembly to timing chain housing nuts.
pump cover to pump body bolts
pump cover to cylinder block bolts (Bottom Bolt First)
outlet pipe to cover bolts
To complete installation reverse removel procedure.
Torque specs are 19 in. or 26mm all except water pump cover bolts which are 124 in or 14Nm
I never torque the bolts just make sure there done in the right order.

there are rubber mounting underneath the car, remove there.

follow the exhaust pipe to the engine, loosening any bolts and nuts holding the exhaust in place.

the exhaust pipe meets the exhaust manifold close to the engine. loosen it there and replace,

the part remaining on the engine (also a much thicker pipe than the pipe) is the exhaust manifold. this must the loosened at the engine itself. normally two nuts per cylinder and your car being 4 cylinder its 8 nuts.

There nuts can be dreadfully tight though, it gets hot there so the expansion and cooling of of the studs and nuts tend to make them tighter over time

U can buy solid expansion joints that u set to the temerature(usually 20 degrees c)