Yes no gasket on cast iron exhaust manifolds. I never use them, 1 time I tried them they failed.
CK5
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1989 K5 - Gradual Learning
- Thread starter shima
- Start date
First 4x4 - learning basic maintenance / upkeep and maybe some small mods.
So am I reading this correctly that the exhaust may not be sealed properly at the cylinder head?
Which would make the O2 sensor read improperly?
Have we discussed this before, on this truck, or no?
Which would make the O2 sensor read improperly?
Have we discussed this before, on this truck, or no?
More details come up.
I think you are starting to get more places to blame.
The color of the sparks makes exhaust leak more probable and as was mentioned that could create some of the symptoms that you have
It has been a little bit since I have checked-in.
My to-do list (diagnosing a stumble/shudder at idle) from the last handful of posts was:
#1:
The spark plug wires were all snug on the plugs. I feel confident that they're connected well.
#2:
A few of my exhaust manifold bolts were quite loose. It was especially bad on both sides up near the firewall. I was using a 1/2" drive socket that is perhaps a foot long to tighten the bolts. Even with my scrawny arms, there was basically no resistance when turning the wrench. I saw in my Haynes that the torque spec is 30 ft lbs... I just cranked them down firmly.
When tightening the exhaust manifold bolts, I was reminded that a while back I had used exhaust putty to seal up some pretty big cracks / gaps in them. When doing that, I had really only looked at my manifolds from above (while sitting in the engine bay). Later this week I am going to look at them from below as well to see if there are any areas that need patching. Once I complete that work, I am going to take it for a long test drive and see how it behaves. When I come home I'll repeat the "turn off the lights" test to check for the glow. After that I am going to move on to the EGR.
Thanks again for everybody's help. Tracking down this issue has felt like a bit of a goosechase but I have learned a ton.
My to-do list (diagnosing a stumble/shudder at idle) from the last handful of posts was:
- Double-check all spark plug wires to make sure they're seated on the plugs correctly.
- Check my exhaust manifold bolts to see if they are loose.
- Look through the EGR system thoroughly and try to get it fixed up.
#1:
The spark plug wires were all snug on the plugs. I feel confident that they're connected well.
#2:
A few of my exhaust manifold bolts were quite loose. It was especially bad on both sides up near the firewall. I was using a 1/2" drive socket that is perhaps a foot long to tighten the bolts. Even with my scrawny arms, there was basically no resistance when turning the wrench. I saw in my Haynes that the torque spec is 30 ft lbs... I just cranked them down firmly.
When tightening the exhaust manifold bolts, I was reminded that a while back I had used exhaust putty to seal up some pretty big cracks / gaps in them. When doing that, I had really only looked at my manifolds from above (while sitting in the engine bay). Later this week I am going to look at them from below as well to see if there are any areas that need patching. Once I complete that work, I am going to take it for a long test drive and see how it behaves. When I come home I'll repeat the "turn off the lights" test to check for the glow. After that I am going to move on to the EGR.
Thanks again for everybody's help. Tracking down this issue has felt like a bit of a goosechase but I have learned a ton.
Tell me more about this exhaust putty, and what it was used on.
What color are your manifolds. Any blue spots? Any crystalized looking areas?
What color are your manifolds. Any blue spots? Any crystalized looking areas?
Here is the putty product I used:
https://www.jbweld.com/product/j-b-extremeheat
My exhaust manifolds are brown; I think they're just cast iron. I haven't seen any blue spots or crystalized looking areas yet but I'll report back if I see anything like that when I look them over later this week.
I don't recall hearing a ticking noise, but I'll keep an ear out the next time I fire it up.
I went out tonight to look over my exhaust manifolds. They have heat shields all over them; there seem to be a couple of styles. The one in my hand was covering cylinders 2 and 4. The shields behind it were covering the other cylinders. There is one more that I can't get off because of a stripped screw. Also half of the shield covering cylinders 2 and 4 is still on... getting that out has been a battle. I'm sure it would be a lot easier to just remove my manifold but I'm being stubborn. Going to continue working on this stuff tomorrow.
I am glad that I'm taking the shields off because I'm finding more cracks beneath them.
you need new manifolds. I would check your cat for plugging up. to much back pressure can add to driveability problems. Like egr codes and stalling.
If you get used, you want them to be the color at bolts. not that blackish blue color. There is a tool made to spread the gap between the ends and center, very handy to help install used manifolds, and not damage head threads or start bolts crooked
I made my own, out of some 1/2" hardware and piece of pipe, but I didn't have to purchase any of it. $12 seems cheaper then buying 1/2" hardware these days.
If you get used, you want them to be the color at bolts. not that blackish blue color. There is a tool made to spread the gap between the ends and center, very handy to help install used manifolds, and not damage head threads or start bolts crooked
I made my own, out of some 1/2" hardware and piece of pipe, but I didn't have to purchase any of it. $12 seems cheaper then buying 1/2" hardware these days.
I think I have a set of manifolds you can have. Those heat shields are a pain but try to reuse them. I can check in the next day or so on if I have any manifolds. That JB stuff is not gonna last long.
Oh and throw the F'ING gaskets away. Hard hit with a scraper both mating surfaces, maybe a light hit with flat file, knock burrs off, bolt'm up and go.
In a similar boat over here Capt, plug wire heat shield isn't enough?
It really comes down to personal preference, I try to use them myself.
Personally I have found after hundreds of heat cycles many manifolds are warped just enough that quality gaskets are needed.
Although the factory did not use them, afters years of use gaskets were the only way I could get some manifolds to seal properly.
Same reason you sometimes need a spreader to install them.
@Capt Ron and @Wes Harden, I have been meaning to replace my cat for a long time now. You guys have been helping me for years so you may remember us talking about it on this thread years ago. It's the original pancake-style cat and we have suspected that it is clogged but have never known for sure.
What do you think about me biting the bullet and just going to an exhaust shop to get everything replaced? It feels like now is a good time, I've just got to figure out whether I want to eat the cost or I want to try to replace some or all of it myself. The past guidance was to just go to an exhaust shop for the cat at least. I am feeling like perhaps I just get it all done.
What do you think about me biting the bullet and just going to an exhaust shop to get everything replaced? It feels like now is a good time, I've just got to figure out whether I want to eat the cost or I want to try to replace some or all of it myself. The past guidance was to just go to an exhaust shop for the cat at least. I am feeling like perhaps I just get it all done.
You can change out the manifolds. Thankfully the old school small block uses large bolts that won’t break like the LS stuff.
Honestly if all you need is a cat that’s all I’d have a shop do unless you wanted to redo the entire exhaust system due to rust, holes or a rotted out muffler.
Or if you just want to update it with a better sounding muffler and new pipes too then that’s a good time to do it.
Honestly if all you need is a cat that’s all I’d have a shop do unless you wanted to redo the entire exhaust system due to rust, holes or a rotted out muffler.
Or if you just want to update it with a better sounding muffler and new pipes too then that’s a good time to do it.
Do the manifolds then get the exhaust shop to put a new cat and any repairs updates you need/want
@Capt Ron I have never not been able to get a good head to manifold seal. I have retorqued when warm normally, and try to always use the fat flat washers on every bolt.
I always try to remove them dead cold, so they don't move.
Never had it done but they could be fly cut flat again.
I reuse the spark plug heat shields always. Keeps the plug wire boots nice and supple. Forget how old my wires are but at least 2 decades, probably 3, 50k+ miles. Several sets of copper AC plugs
I always try to remove them dead cold, so they don't move.
Never had it done but they could be fly cut flat again.
I reuse the spark plug heat shields always. Keeps the plug wire boots nice and supple. Forget how old my wires are but at least 2 decades, probably 3, 50k+ miles. Several sets of copper AC plugs
I have some updates!
- I went to the junkyard and picked up some new-to-me exhaust manifold heat shields. I also grabbed some spark plug wire separators and the little connector that is on the wire end for the temp gauge (mine is partially burned). It all came off of a pretty sweet looking G20. No clue why it was in the yard because it looked to be in nice shape.
- I patched up the crack on my passenger-side exhaust manifold:
- Then I installed the new-to-me heat shields that I got from the junkyard. Originally covering the manifold by cylinders 2 and 4 was a wrap-around heat shield that was a PITA to get off. I replaced that with a normal heat shield:
- I double-checked all of the spark plug wires and headed out for a test drive. The Blazer felt pretty good overall. The shake is still there at stoplights but like I said in an earlier post it isn't as severe. I don't think it would die on me anymore.
- When I parked in the garage, I turned off all the lights and could still see the rare flashing that I described earlier in the thread. I didn't run it long because I had the garage doors closed to keep light out.
- I thought to myself that I still had the new coil sitting there on the shelf. Went ahead and installed that. Took it for another test drive, no change.
