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I am getting ready to pull the intake manifold off to replace the knock sensors... I am wondering what else should I replace while I have access to the rear of the engine behind the manifold?? I have the PCV Hose/tube on order as I know the one in there is shot....
Look at the oil sensor for any issues, preemptively changing would be a cost choice since they are a known issue. Relocation is another option.
Personally, I would bypass the throttle body just because future removal becomes easier.
Make sure to vacuum the area really good before removal to try to prevent dirt going into intake ports. Then vacuum the intake ports once the intake is off.
Look over the PCV and the AIR piping really good for cracks, etc. You might want to swap out the rear AIR check valve as another preemptive change.
Lastly, there is a TSB from GM on water intrusion in the knock sensors. Pull the TSB and do the job while in there. It involves building a dam of RTV to keep water out of the knock sensor.
Look at the oil sensor for any issues, preemptively changing would be a cost choice since they are a known issue. Relocation is another option.
Personally, I would bypass the throttle body just because future removal becomes easier.
Make sure to vacuum the area really good before removal to try to prevent dirt going into intake ports. Then vacuum the intake ports once the intake is off.
Look over the PCV and the AIR piping really good for cracks, etc. You might want to swap out the rear AIR check valve as another preemptive change.
Lastly, there is a TSB from GM on water intrusion in the knock sensors. Pull the TSB and do the job while in there. It involves building a dam of RTV to keep water out of the knock sensor.
All I can think of before my first cup of coffee
I recently had to remove the intake manifold on my 97 C5 74K miles because the intake gaskets was leaking and oil pressure sensor was bad. I replaced the intake gaskets, oil pressure sensor, and pcv hose runs on right side of the engine. I didn't replace the knock sensors, perhaps I should of now I'm thinking about it. There was also faint coolant burning smell, one of the coolant pipe to the cylinder head was rusty so i replaced all four coolant pipe gaskets to cylinder head. I didn't notice any water around the knock sensor cover so I didn't put rtv sealant around knock sensor cover. Since I re[placed all four coolant pipe gaskets i figure there should be no coolant leak in there for another years. When I did this i just bought the car had no money or time to research to upgrade intake that's in the car. It would of been nice to at that time to upgrade the stock intake. Just saying.
Do you know my car has LS2 or LS3 intake?
I am getting ready to pull the intake manifold off to replace the knock sensors... I am wondering what else should I replace while I have access to the rear of the engine behind the manifold?? I have the PCV Hose/tube on order as I know the one in there is shot....
Thanks,
Ant..
there's a sensor behind back of the intake you should change if you want to because you have to pull the intake to replace that one. When I pulled my intake to relace the intake gaskets i replaced the oil pressure sensor because it was not reading proper temp. but I didn't replace that sensor by the oil pressure sensor because that sensor wasn't bad but now I'm thinking I should have along with the knock sensors. If that sensor goes bad I have to pull the intake again. Oh one pointer I read is do not over tighten the oil pressure sensor read if you do they go bad fairly quick. Tor que to spec.
Look at the oil sensor for any issues, preemptively changing would be a cost choice since they are a known issue. Relocation is another option.
Personally, I would bypass the throttle body just because future removal becomes easier.
Make sure to vacuum the area really good before removal to try to prevent dirt going into intake ports. Then vacuum the intake ports once the intake is off.
Look over the PCV and the AIR piping really good for cracks, etc. You might want to swap out the rear AIR check valve as another preemptive change.
Lastly, there is a TSB from GM on water intrusion in the knock sensors. Pull the TSB and do the job while in there. It involves building a dam of RTV to keep water out of the knock sensor.
All I can think of before my first cup of coffee
I agree!
The 97-2000 have the coolant steam cross over piping under the intake. The 2001-2004 do not. Just pointing out some design stuff between years.
Use compressed air and blow out all the area around , on top and the sides of the manifold. There WILL be a nice collection of sand and dirt!
IF, you want a LITTLE more Hp, you can change out the early intake manifold with any 2001+ and or a ZO6 manifold (SAME) They flow a little more air under load.
I just added sealant to my knock sensor close out plugs. I left a very small area to allow the well to vent any pressure changes.
Make sure that the knock sensor wells are clean and dry. If they have OIL in them, you have to change out the valve valley cover seals. Water comes from getting the engine wet WASHING IT!
The Knock sensors MUST be properly installed (Torqued to the proper spec) to work properly. Inspect the KR Sensor wire harness pig tale for any damage and repair or replace.
REPLACE THE INTAKE MANIFOLD PORT SEALS!!! PERIOD! EASY JOB!
When you loosen ALL the intake manifold bolts, you can NOT remove the two most rear bolts. They hit the COWL and wont come out. When you TRY to slide out the manifold, the two remaining bolts will hang up and prevent you from removing it.
Cut a small 3/4" long piece of vacuum line and slit it long ways. Pull UP the bolts and slip that piece onto the shank of the bolts to keep the bolts UP to prevent them from dragging on the engine. The manifold will slide right out. NOTE! If you hold the manifold UP when you slide it out, you will drag less DIRT into the ports.
VACUUM out all the ports and the valve valley cover plate. Clean the head surface with solvent to remove any grime. Apply a just a little dielectric grease (very thin film) to the FACE of each port O ring seal just before you reinstall the manifold. It helps the port seal SLIDE as the intake manifold bolts are retorqued.
The inside of your OEM manifold will be COATED in excessive PCV Blow By OIL!! Be prepared to SOP out the oil that collects inside the plenum, flush with some brake parts cleaner and then scrub out the inside with hot water and degreaser. If it were ME, I would install a quality Catch Can while you in the mood to do engine service!
I have already changed the oil pressure sender last week without pulling manifold and if I would have known I was gonna end up pulling the manifold I would have waited... But the sensor is brand new.....
Things I will need to get..
1) All gaskets / orings
2) Rear air check valve..
3) oil pressure sender - already done.
4) PCV Tube - Ordered -, should be here tomorrow
5) Knock Sensors and harness - better to just change it all I figure ..
6) Intake Manifold Port Seals
7) Catch Can
Think that's it for now , Will inspect everything once apart... I would like to get a newer manifold but not needed at this time.. I'm on a tight budget right now but maybe later.. Car is fast enough for me as I am an old man and don't need anymore tickets on my record... I will post pics as I go...If anyone needs any specific pics or anything feel free to ask...
Found the problem with the knock sensors,.. Got the manifold off and found The friggen wire harness was not connected behind manifold ( That would explain the codes for that )..
, Glad I didn't order the new knock sensors yet... I ordered a new water pump for a piece of mind while I am here ( Not sure how old the one in there is).. I ordered a new felpro gasket kit for the manifold as well.. no reason to change a bunch of parts that are still good.. The manifold was not hard to get off at all so I can always do it again if needed..
Ant...
Last edited by ant-knee470; 03-11-2018 at 03:36 PM.
If you have it apart that far, consider relocating the oil pressure sender. I added a gauge to mine. In case the sender quits, you can still verify that you have oil pressure.
The sender unit in the picture above and used for relocation with a NPT tee or other fitting is a 97-004 Buick Le Sabre unit which has NPT threads. The LS version has metric threads.
I am thinking that the existing coolant air bleed pipes coming from the rear ports on earlier cars will not fit under the later manifold and will have to be relocated also, should you change your mind and decide to install a later manifold. Maybe Bill can verify.
I use a large rubber band between the two rear manifold bolts to hold them up out of the way when installing the intake manifold.
Engine valley cover and steam pipes are all closed up and back together, Parts came in today.. It's getting ready to rain outside so I will putt the intake back on tomorrow.. I was unable to find a new cam shaft sensor as it is discontinued.. So I just put the old one back in..
Well should have it all back together tomorrow then Monday it is going to the shop to get a new convertible top put on, I can't wait...HEHE!!!
Thanks,
Ant...
Last edited by ant-knee470; 04-05-2018 at 05:00 PM.
If you have it apart that far, consider relocating the oil pressure sender. I added a gauge to mine. In case the sender quits, you can still verify that you have oil pressure.
Good idea....someone put together a parts list with AN fittings/hose to do the oil pressure sensor relocation....but I can't find it right now.
Good idea....someone put together a parts list with AN fittings/hose to do the oil pressure sensor relocation....but I can't find it right now.
Thanks for the info, But I prefer to leave it as it is... If I have to change it in the future I can pull it in 15-20 mins without removing the intake... No biggie!!!
Yipppeee, Car is all back together and it seems as if it was a success, CEL is now off and it does not seem to be coming back on... Heres what all I did,
New Intake Manifold Gaskets ( Felpro )
New Rear Air Check Valve
New Steam Pipe Orings
New Water Pump
New radiator
New Thermostat
All new coolant Hoses
New Knock Sensors
Car is running great... And if the CEL does not come back on Ill be happy...
Ant...
Last edited by ant-knee470; 04-06-2018 at 08:35 PM.
Ok,
Been driving car for 2 days now and no more CEL coming on... Thank god... I really hate that light. Thanks to everyone for the help, Much Appreciated...
I am getting ready to take the car to the top shop... Hope they do a good job, I hate the idea of someone else putting my top on but I don't really have any idea on how one goes on so better to let someone who I hope knows what they are doing... Should have my car back in a couple days..
03-01-2018, 06:39 AM
98- C5 pulling intake manifold / what to change?
EASY JOB! 
Be prepared to SOP out the oil that collects inside the plenum, flush with some brake parts cleaner and then scrub out the inside with hot water and degreaser. If it were ME, I would install a quality Catch Can while you in the mood to do engine service! 
