04 5.3 rough idle after head swap (castech failure)

[04z71crew]

Hey guys, 

 

I had some bad luck recently with my 2004 silverado z71 5.3. I had the 706 castech heads and they finally gave out on me causing the truck to overheat. Took it to the shop and they wanted 3 grand to do head gaskets using the same heads apparently they were clueless to the TSB on the castech heads. I found a guy that rebuilds heads and picked up a set of 799’s and had them milled .030. It took me 3 weeks off evenings and weekends but I finally got the new heads and gaskets on with every bolt double checked used properly torqued specs/angles etc. I also replaced all lifters,trays, and pushrods, oil sending unit, knock sensors, heater hoses, and upgraded to the larger radiator from 2005 and up trucks LOL. The truck fired up first try and runs great when cold, however when it gets to operating temp the idle is very rough and acts like its missing. Should I be looking for a vacuum leak? any suggestions? Thanks for the help. 

 

 

 

 

 

[dtnel78]

Check the PCV valve, fuel venting system? Is it holding a vacuum? That's a few things to check.

What was the head TSB? I have a 04 with the 4.8 so it may not apply but worth checking as you never know. 125,800k miles on it and runs good as the day I bought it except it needs a exhaust manifold bolt repaired on left rear of engine which I'll do once it gets warm. Also have the knock sensor TSB to do on it and replace both knock sensors as I have a code already.

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[silveradosid]

get it hooked up to a scanner and check miss fire counts on the each of the cylinders might be a bad coil when it gets hot or sticking injector

[txab]

3 hours ago, dtnel78 said:

Check the PCV valve, fuel venting system? Is it holding a vacuum? That's a few things to check.

What was the head TSB? I have a 04 with the 4.8 so it may not apply but worth checking as you never know. 125,800k miles on it and runs good as the day I bought it except it needs a exhaust manifold bolt repaired on left rear of engine which I'll do once it gets warm. Also have the knock sensor TSB to do on it and replace both knock sensors as I have a code already.

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http://ww2.justanswer.com/uploads/Bluegorilla/2008-12-05_142924_Coolant_loss_5.3.pdf

[04z71crew]

quick update thanks for the replies it ended up being the oxygen sensor on bank 1 before the cat. Replaced with ac delco unit and it cleared the CEL and now idles like it should! 

[04z71crew]

On 2/17/2019 at 5:36 AM, dtnel78 said:

Check the PCV valve, fuel venting system? Is it holding a vacuum? That's a few things to check.

What was the head TSB? I have a 04 with the 4.8 so it may not apply but worth checking as you never know. 125,800k miles on it and runs good as the day I bought it except it needs a exhaust manifold bolt repaired on left rear of engine which I'll do once it gets warm. Also have the knock sensor TSB to do on it and replace both knock sensors as I have a code already.

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Thanks for the suggestions see above reply in my case it was the driver side pre cat 02 sensor. 2 of my exhaust manifold bolts were broken off on my old 706 heads if they are flush weld a nut on top and try to slowly back it out. Worst case scenario they actually make brackets for busted exhaust manifold bolts that will work to create a seal if you cant get them out not worth drilling IMO. APDTY 028218 Exhaust Manifold To Cylinder Head Leak Repair Clamp Fits Front Right or Rear Left On 4.8L 5.3L 6.0L Engine On Escalade Avalanche Silverado Pickup Tahoe Express Van Denali Sierra Pickup Savana Yukon Hummer H2 (See APDTY-028253 For Other Side) https://www.amazon.com/dp/B00I3LLVS8/ref=cm_sw_r_cp_api_i_jrMBCbRYVA70Z

 

 

[Black02Silverado]

Glad you got it fixed.   Just curious as to how many miles are on the truck.  The valve covers looked really clean.  Also the cylinders looked in great shape as well.  Not much carbon build up.

[04z71crew]

On 2/21/2019 at 6:05 AM, Black02Silverado said:

Glad you got it fixed.   Just curious as to how many miles are on the truck.  The valve covers looked really clean.  Also the cylinders looked in great shape as well.  Not much carbon build up.

173K miles. I am OCD for changing the oil on time or EARLY lol. The first photo is of the motor after I pulled the heads. There was quite a bit of carbon buildup that took quite of bit of elbow grease to remove but I figured I was already there why not do it. What it did notice is that there was almost 0 sludge buildup at all. The power difference now with the new heads is very noticeable or it could be its just because it hasn't been that clean since new. It has been a couple of weeks and I just changed the oil for the second time get the residual dirt/grime that may have accumulated during the repair. No CEL, no issues and I just upgraded my 105 alternator to a 145 amp. 

[dtnel78]

173K miles. I am OCD for changing the oil on time or EARLY lol. The first photo is of the motor after I pulled the heads. There was quite a bit of carbon buildup that took quite of bit of elbow grease to remove but I figured I was already there why not do it. What it did notice is that there was almost 0 sludge buildup at all. The power difference now with the new heads is very noticeable or it could be its just because it hasn't been that clean since new. It has been a couple of weeks and I just changed the oil for the second time get the residual dirt/grime that may have accumulated during the repair. No CEL, no issues and I just upgraded my 105 alternator to a 145 amp. 

I change the oil every 3 months or 3kmiles at the dealers expense. I was a sucker when I bought it Jan 15, 2005 brand new but oil has went up and they still and always will change my oil for free per the contract. Engine goes out I'll put another in and let them change that oil free as they look at the VIN# in the dash so I'll drive it till I can't keep the cab from freezing me out. Cheaper than buying a new or newer car either way. [emoji16]

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[dtnel78]

Thanks for the suggestions see above reply in my case it was the driver side pre cat 02 sensor. 2 of my exhaust manifold bolts were broken off on my old 706 heads if they are flush weld a nut on top and try to slowly back it out. Worst case scenario they actually make brackets for busted exhaust manifold bolts that will work to create a seal if you cant get them out not worth drilling IMO. APDTY 028218 Exhaust Manifold To Cylinder Head Leak Repair Clamp Fits Front Right or Rear Left On 4.8L 5.3L 6.0L Engine On Escalade Avalanche Silverado Pickup Tahoe Express Van Denali Sierra Pickup Savana Yukon Hummer H2 (See APDTY-028253 For Other Side) https://www.amazon.com/dp/B00I3LLVS8/ref=cm_sw_r_cp_api_i_jrMBCbRYVA70Z
 
 

I have the pro maxx kit which I'll use when I do it this summer. Have to get new air compressor wired up so I can use the small 1/4 drive Ratchet with a drill adapter on it.

I'll use the kit to make side money as well for other vehicles as once you get it lined up on the vehicle and step drill the heads then you only need to remove the last remaining bits of threads and chase it with a thread chaser before installing a new gasket kit.

Not sure if I should use the Mini Ductor for the remaining ones as they use Loctite for OEM assembly of the engine and I don't want to melt the aluminum heads. I'll need to check some temps on stuff before I make that decision though. IF I can loosen the Loctite by heating the bolts then that would save time and possibly broken exhaust manifold bolts.

I'll make a decision real soon as I have to do the knock sensors and need to pull the upper intake Plenum which would be the ideal time since if I have to pull a head by some odd reason this would save me time and money on gasket kits.

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