I have a 1991 L98 and need to change out the egr valve (code 32). I'll be attempting this myself and need help/guidance on removing the plenum. Can some provide the steps and/or pics? Thanks!

 

The plenum itself is fairly easy to remove and pretty staight forward. If I remember correctly one of the bolts for the EGR valve is a real bear to remove though.

 

Straight forward job, remember to mark the bolts 2 different sizes if I remember right. Be careful with TB if you still have water hoses running into it drain down the radiator a little first so you have less mess. You will need new upper runner gaskets. Make sure you disconnect the brake booster line drivers side rear also the MAT is back there under plenum also be careful of your vacuum lines 2 on passenger side 1 up front drivers side . I would remove the TB from plenum and lay it out of the way disconnect the TPI connector & IAC . You can get an off-set wrench to get at the EGR bolts. Good Luck

 

Usually the plenum is stuck fast to the runners so needs a little assistance with a soft hammer or 2 x4.

 

I would remove the TB from the plenum to ease the job. Don't forget the MAT connector under the plenum rear, the brake booster vac line at the L rear, the two vac lines at the R rear and of course the small vac line under the TB.

Indeed one of the EGR Valve bolts is a PITA; I used a small 6pt box-end and had to pry on it to break the bolts loose. Some PB Blaster on those bolts wouldn't hurt the effort either.

I suggest you pick up a Fel Pro top end gasket set at Auto Zone; you can use the other gaskets next time you're "in there".

This is a geart time to do the TB coolant bypass so that you never again need to drain coolant to service the plenum or anything below it.

 

What ever you do, do not hit the runners with anything. They dint very easily. Don't ask me how I know.

 

Once the TB is removed tap the plenum on the front the EGR won't allow you to tap it enough on the rear

 

There are two semi-hidden runner to manifold bolts that some forget to spot and remove when pulling or loosening the runners.

They're accessed from the opposite sides of the engine. The one on the passenger side front is accessed by attacking it from the Driver's side. The one on the Driver's side rear is accessed from standing on the passenger side of the engine.

A long extension is needed too.

Jake

West Point ROCKS!

 

To just remove the plenum he doesn’t need to mess with removing the runners or the lower bolts. Just needs access to the EGR

 

From memory, here's how I did mine. My engine was a 86 so may be slightly different from yours.

Removed the throttle body and throttle and trans cables.

Use two wrenches to remove the power brake line at the rear of the plenum.

I removed both valve covers to allow easier access to lower runner bolts.

Use a long extension to access the semi-hidden bolts. You have to bend down low and look under the plenum to see them. One's in the front passenger side and the other rear, driver's side.

Removed all runner bolts, setting them aside in a manner so you'll know which bolt goes where. A piece of cardboard with holes punched in it can be used to place the bolts.

On my first removal of the plenum, I had to use a thin blade screwdriver to break the runner to plenum seal. Insert the tip of the screwdriver into the mating points of the plenum and runners and gently tap with a hammer. Then rock the plenum back and forth until it breaks free. A few WHACKS with a rubber mallet may be needed.

If you engine is like mine was there are two bolts at the very front of the block that hold the fuel lines locked in place. Remove four fuel rail bolts and rails can then be gently pried up.

On re-assembly don't forget to plug in the air temp sensor on the underside of the plenum ALSO, use Anti-seize on threads of all the bolts.

Clean all the gasket mating surfaces to remove any gasket material still stuck. BE SURE TO CORRECTLY MATCH the new gaskets to their mounting locations. The FelPros I used were side specific and if mis-installed will result in a vacuum leak.

Gradually re-torque all the bolts, alternating from side to side, top to bottom.. Go over the bolts several times to make sure the torque holds. Sometimes when you tighten one bolt that'll loosen another one, usually on the opposite side of the engine.

It's been a few years since I've pulled the plenum, so I'm going from memory on this. If I missed something, I hope someone will address it.

Hope it helps.

Jake

West Point ROCKS!

 

To insure a positive seal, I remove the runners, do what I had to do, then use all new gaskets to reseal the runners and plenum.

Sure, you can try a short-cut, but if it doesn't seal correctly the job will have to be done all over again.

Same thing with those who try to remove and replace the timing chain cover without loosening and slightly lowering the oil pan. Most times there'll be an oil leak.

I prefer to bite the bullet rather than spending days trying to figure out why the engine doesn't run well after the work is completed.

However, it's his call; to each his own. What I posted is how I do it.

Jake

West Point ROCKS!

 

I would re torque the lower bolts but not remove the runners

 

Just an additional tip:

I have a 1990 by the way....


When reinstalling the plenum - line up the angled bolt holes first. Then thread in the the straight bolts and sequence the tightening. The plenum is an aluminum based alloy and is really soft. The threaded holes in the plenum strip really easily!!

Some people don't use gasket sealer on the plenum to runner gasket, but I used a thin film of silicone. Don't want an intake leak and have to take it apart again.

Good Luck!

Flatbush862

 

Two extra tips:

After whacking my plenum a few times with a rubber mallet, I ended up using a crowbar and a block of wood to pry up on the plenum. Seemed much easier for breaking the plenum loose after bolts were removed.

Also, aluminum is soft. Be careful what you use to remove old petrified gaskets. You could gouge the aluminum if not careful.

 

Yep, I forgot to mention it, but I always use sensor safe silicone sealant on bolt sides of the gaskets too.

Over the years I use to have so many problems sealing the intake on both SBC and BBC that I became **** about sealing those suckas.

Last one that leaked on me was when one of my engines was waved off the starting line because the rear China Wall was leaking oil. That was so embarrasing I vowed to never let that happen again.

Jake

West Point ROCKS!

Jake

 

Code 32 is a fault with the EGR circuit. The EGR could be the problem but it also could be the EGR Solenoid, the electrical connectors to the solenoid or any of the vacuum lines to the solenoid and from the solenoid to the EGR . A very close inspection of the wiring and vacuum lines is always a good place to start. Changing the EGR is not too hard but it would be annoying to change it and still have Code 32.