98 Honda Civic EX Exhaust.

First you must remove the A exhaust pipe that is under the oil pan. Make sure use a penetrating lube, like WD-40 on all exhaust nuts. If there is a lot of rust, you can remove the 3 or 4 manifold nuts, the 2 bolts for the bracket to the block, and unhook the exhaust hangers, and move the whole exhaust out of the way. Drain the oil, then remove the support brackets, then all the 10mm oil pan bolts and nuts. The oil pan can seem glued in place, pry it loose without bending it. Make sure you get any steel rings off from around the studs, they are part of the oil pan gasket, and tend to stick to the block.

any car made after 94 must have 02 sensor ,start at exhaust manifold ta engine and follow it down at some point you will see something looking like a spark plug sticking out of exhaust pipe before the cat and a second 02 sensor after cat .

changing the exhaust system can alter the gas flow and may create problems for the sensors . The HO2s sensor and the O2 sensor may now be operation on the edge of the parameter settings and any exhaust coating on the sensors may be affecting their performance. Run fault codes to check the sensors and sometimes removing them and cleaning them in vinegar to remove the coating will improve the situation. What ever is the problem if it started after the manifold change then that is the area in which to seek answers.

On the 1998 Honda Civic with the D16Y5 and D16Y7 engines, the Catalytic Converter is part of the Exhaust Manifold. If you have the D16Y8 engine, the Catalytic Converter is separate from the Exhaust Manifold, and is directly between the 1st and 2nd Oxygen Sensors.

Here is a diagram of the D16Y5 and D16Y7 Exhaust Manifold and Catalytic Converter: http://www.4shared.com/document/zvR9UsXJ/1998_Honda_Civic_D16Y5_D16Y7_C.html


I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

see instructions below from autozone.com. Also, please see my tip at http://www.fixya.com/cars/r5929960-s_thermostat .

2.3L and 2.4L Engines

See Figure 7
When adding coolant, it is important that you use GM Goodwrench DEX-COOL® (orange colored, silicate free) coolant meeting GM specifications. On these vehicles, if silicated coolant is added to the system, premature engine, heater core or radiator corrosion may result. In addition, the engine coolant will require change sooner; at 30,000 milee or 24 months.

1. Disconnect the negative battery cable.
2. Properly drain and recover the coolant to a level below the thermostat.
3. Unfasten the cover-to-outlet pipe bolt, which is accessible through the exhaust manifold runners.
4. Raise and safely support the vehicle.
5. Disconnect the radiator and heater hoses from the outlet pipe.
6. Unfasten the outlet pipe-to-oil pan bolt and the cover-to-outlet pipe bolts.
7. Remove the thermostat, then clean the old gasket material from the mating surfaces.

Fig. Fig. 7: Thermostat removal and installation-2.3L and 2.4L engines

To install:

1. Position the thermostat in ite correct location, then install the cover-to-outlet pipe bolt. Tighten the bolt to 10 ft. lbs. (14 Nm).
2. Install the outlet pipe-to-oil pan bolt. Tighten the pipe-to-oil pan bolt to 19 ft. lbs. (26 Nm) and the pipe-to-transaxle bolt to 40 ft. lbs. (54 Nm).
3. Connect the radiator and heater hoses to the outlet pipe.
4. Carefully lower the vehicle.
5. Install the cover-to-outlet pipe bolt through the exhaust manifold runner.
6. Properly fill the cooling system, then connect the negative battery cable.

It is a big job that requires dis- assembly of the exhaust system as well as other components. The most difficult part is removing the exhaust header pipe to allow the pan to drop, this will require a torch set to heat the bolts for removal. Unless you have these tools, you will have a very difficult time performing this repair.

The 96-98 Civic EX came with an OBD2A D16Y8 engine. That is the only engine that will go in as a direct replacement with your current engine ECU. It's an SOHC VTEC engine that has two extra connections not found on the other 96-98 Civic engines - a VTEC solenoid and a special oil sensor used to determine if VTEC engagement is possible. If you swap in an older Civic engine (92-95 generation) you'll have to convert the car to OBD1 (requires a special adapter hardness) and run the ECU that goes with whatever engine you use. This will break functionality of your OBD2 diagnostics port, and depending on which state you live in will cause you to fail emissions checks. If you install a D16Y8 engine from a 99-00 Civic EX, you will have to swap the intake and exhaust manifolds from your old engine to the new engine, and you will be able to continue to run your existing OBD2A wiring and ECU. The 99-00 Civic EX engines have additional sensors, since those engines are OBD2B. The easiest fix would be to find a SOHC VTEC D16Y8 from a 96-98 Civic EX, as it would be a direct plug and play replacement.

Changing the oil pan gasket on a GMC Yukon XL is realtively simple, but does require removal of the exhaust pipe. You will need a new oil pan gasket and a new exhaust pipe flange gasket.
Put the car on ramps or jacks to access the undercarriage.
Remove the exhaust pipe by removing the 3 nuts holding the exhaust pipe flange to the exhaust manifold. These nuts often rust and prior application of penetrating oil may be required to remove them without damage. Once the pipe is unbolted, work the exhaust system loose from the hanging brackets. In most cases the entire system does not have to be removed since there is enough room to remove the pan with only the front hangers removed.
Drain the oil from the engine
Remove the 10 mm bolts holding the pan to the block.
Remove the old gasket material and scrape any remaining gasket from the block and pan.
Install the new gasket. Forma-Gasket or a similar product may be used in small quantities to "glue" the new gasket in place and prevent shifting while the pan is reattached to the block.
Reinsall the 10 mm bolts in a cross pattern to ensure the gasket is compressed evenly. Do not overtighten the bolts.
Replace the pipe to flange gasket between the exhaust pipe and the exhaust manifold with a new part.
Reattach the exhuast pipe to the hangers.
Install the 3 bolts connecting the pipe flange to the exhaust manifold.
Fill the engine with oil.

You need to drop the exhaust then the pan comes down. BUT if you are doing this because the exhaust shield has rubed through the paint making the pan rot out in that one spot. then once you remove the exhaust grind the pan where the hole is and wire brush an old copper penny and use ( J B weld ) epoxy http://www.jbweld.net/index.php
to stick the penny over the hole, then with a hammer tap the exhaust shield back so it doesnt touch the pan and bolt it back up.

dropping the exhaust is tricky, once you have the 4 oxyigen sensors unpluged remove the 4 exhaust manifold nuts off the studs (you might need to use a torch to heat them up) then unbolt the flex pipe and you will have 1 more bolt in the middle of the system that as you crank it out the exhaust will come down

Removal Procedure
1. Disconnect the negative battery cable.
2. Drain the engine oil from the engine crankcase.
3. Remove the exhaust flex pipe retaining nuts from
the exhaust manifold.
4. Remove the exhaust flex pipe retaining nuts from
the catalytic converter or the connecting pipe.
5. Remove the exhaust flex pipe.
6. Remove the oil pan flange–to–transaxle retaining
bolts.
7. Remove the oil pan retaining bolts.
8. Remove the oil pan from the engine block.
Cleaning Procedure
1. Clean the oil pan sealing surface.
2. Clean the engine block sealing surface.
3. Clean the oil pan retaining bolts.
4. Clean the oil pan attaching bolt holes in the engine
block.
5. Clean the oil pan scraper.
Installation Procedure
1. Coat the new oil pan gasket with sealant.
Important : Install the oil pan within 5 minutes after applying
the liquid gasket to the oil pan.
2. Install the oil pan to the engine block.
3. Install the oil pan retaining bolts.
Tighten
Tighten the oil pan retaining bolts to 10 NSm (89 lb–in).
4. Install the oil pan flange–to–transaxle retaining
bolts.
Tighten
Tighten the oil pan flange–to–transaxle bolts to 40
NSm (30 lb–ft).
5. Install the exhaust flex pipe.
6. Install the exhaust flex pipe retaining nuts to the
exhaust manifold.
Tighten
Tighten the exhaust flex pipe–to–exhaust manifold
retaining nuts to 35 NSm (26 lb–ft).
7. Install the exhaust flex pipe retaining nuts to the
catalytic converter or the connecting pipe.
Tighten
Tighten the exhaust flex pipe–to–catalytic converter
or connecting pipe retaining nuts to 35 NSm (26 lb–ft).
8. Connect the negative battery cable.
9. Install the oil pan drain plug.
Tighten
Tighten the oil pan drain plug to 35 NSm (26 lb–ft).
10. Refill the engine crankcase with engine oil.