Originally Posted by panthera999

wasn't able to take pics, but here's the relevant description. Use the maintenance manual, with the changes i mentioned below.

This only applies to the 4.2 na, not the sc or the 5.0. But if the jag pn is aj88912, you can buy this: https://www.amazon.com/dp/b000iyzhni...roduct_details

the only type to buy is the one piece, metal gasket, metal impeller, machined gasket surfaces, oring ac delco professional 252-800 pump. $60 on amazon. Look at the pics in the url. If you have another brand built the same way, use it.

The one i pulled was a leaking pos, two piece (for extra bolts and leaks), paper gasket (for a crappy fit), not oring (how the hell do you seal the fitting without an oring? A bucket of permatex?). Damn, the one that was on there was crap. It didn't have jag on it, but if jag uses a two piece without an oring, shitcan it and get something that's correctly built when replacement time comes. Btw, the jag unit is $350 or so.

The other important thing is that the manual says to remove the throttle body and the thermostat assembly. You don't have to do this. The necessary hoses fold out of the way to give you plenty of ratchet room.

The process:

The only unusual tool is a hose clip pliers. Since you unclip a few hoses, this speeds up the job a whole lot faster than trying to use regular pliers on these things.

1. Remove the engine cover and the air intake assembly that connects to the throttle body. Uncllip the hose to the valve cover and rotate it out of the way. Fold the intake back over the engine.
2. Open the coolant reservoir cap. Drain the coolant into a clean bucket -- you can reuse it unless it's time for a change, anyway. For me, a ten liter bucket was plenty. My guess was 8-9 liters drained out. It will come out fast if you remove the plug.
3. Unclip the two large hoses at the thermostat assembly. Unclip an in-the-way hose to the egr area and fold it back. Remove the throttle body electrical connector and fold it out of the way. You'll see what blocks access to the pump and pulley.
4. This is a nice time to replace the two large hoses, and any others you want going to the throttle body and egr area. With the hose clip tool, replacing the hoses is very easy.
5. Break loose the three bolts on the pulley. Don't remove them.
6. You need to un-tension the belt tensioner. Needs a good long 3/8" wrench to lever it over -- it's pretty strong. Slip the belt off the tensioner pulley and release it. (i chose to replace the belt and tensioner as a pm, but you don't have to.)
7. Back to the pump. At this point, you'll have plenty of room to do the job. Put a pan under the area to catch dried coolant, dirt and remaining coolant.
8. Remove the 3 bolts on the pulley. Set the bolts and pulley aside.
9. Two piece pumps have 7 bolts: 2 10mm and 5 8mm. If you put in a one-piece pump, the 2 10mm are no longer needed, as it uses only the 5 8mm bolts. If the bolt threads are covered with dried coolant and crap, use a metal brush to clean them. Torque values assume clean threads.
10. Remove the crappy two piece pump, examine what a crappy part it is, and shitcan it. Did i say it's a crappy design? Anyway....
11. Completely clean all mating surfaces, including the place where the pump inserts into the engine with the oring. Likely old permatex all over the place from a mechanic's effort to compensate for a crappy pump design with paper gaskets. Some use permatex on the mating surfaces, but you don't need it if you're using the metal gasket with the red sealing points (i didn't and don't recommend it with this pump). I was advised by by mechanic to put on a very light coating of silicone lube on the red sealing surfaces, plus a very light coating on the oring. Just enough "to shine them up", he said. This allows them to smoothly compress across their mating surfaces when torqued, and lets the oring slip cleanly into place. If the metal gasket is a bit distorted, gently straighten it out on a tabletop. If it is severely distorted in shipping, get a replacement. Remember, the only fluid sealing points on this installed pump are the oring and the red gasket mating points on the metal gasket.
12. Make sure the oring fully seats in the fitting. This is one reason for the silicone on the fitting hole..
12. The five 8mm bolts are torqued to 8nm +90 deg. Torque in an x-pattern, of course. The pulley bolts are 10nm +45 deg. Some choose to put on blue threadlock, or if you want to bust some mechanics ***** later on, red threadlock.
13. Assemble everything back. Doublecheck your work. Refill the coolant system. I didn't need to bleed mine. Make sure your air intake hose is fully seated, all around their lower connection and the throttle body. Easy mistake to make is partial seating of intake.

It's about two hours including time for a refreshing beverage of your choice. On a scale of 5, where 1 is changing your oil and 5 is rebuilding your transmission, this is a 2.

Cheers