Time to replace my plenum pan and gasket... have a couple questions - JeepForum.com
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post #1 of 29 Old 09-04-2012, 12:34 PM Thread Starter
B93
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Time to replace my plenum pan and gasket... have a couple questions

So, before I start asking questions, the vehicle in question is a stock 1998 5.9 Limited. 210,000 kms on it.

I've been pinging under load around 3000 rpm for a little while now, so I'm just wondering what else I should check while I have the intake off - what will be damaged by the detonation?

The engine has also gotten very hot a few times in the past (the connector for my e-fan was loose... fixed it by cutting out the connector and soldering the wires directly). It never got to the point where the engine was smoking, with the exception of one time when I let a dealership look at it Any suggestions on what I should clean or expect to replace due to that?

Thanks for any help guys I'd like to get my engine back in a healthy state, and then start increasing its power

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post #2 of 29 Old 09-04-2012, 01:15 PM
PolkaPower
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The detonation hurts the pistons and cylinders. You won't be able to see that. While you have it off it's good to replace the cap and rotor, cam shaft sensor, valve cover gaskets if they are leaking, coolant return hose, and anything else that's hard to reach. Make sure you cover the valley and scrape off the old gasket really well then shop vac it up. I soaked my intake in degreaser like ten times, rinsed it with the hose, and let it dry overnight. Don't use the intake end gaskets my buddy did and he's leaking oil again. Use a good RTV like Permatex or Right Stuff and lay a thick bead in place of them. Let it cure for about half hour before installing the intake. It's easy but takes a long time. I also replaced the coolant output pipe that bolts to the intake. Mine was nasty.
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post #3 of 29 Old 09-04-2012, 01:48 PM
HighLonesome
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Weld an aluminum plenum plate to the intake manifold and never worry about it again is my advice. I can't do that with my older ZJs due to the EGR ports. They clog and the only way to clear them is remove the plenum plate and ream. You needn't worry about such limitations.
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post #4 of 29 Old 09-04-2012, 01:53 PM
errorcode3
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just buy the huges kit, comes with a ton of stuff you need, pretty decent instructions (aside from pulling the intake)

98 - Slate 5.niner. minor mods
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post #5 of 29 Old 09-04-2012, 02:04 PM Thread Starter
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Quote:
Originally Posted by PolkaPower View Post
The detonation hurts the pistons and cylinders. You won't be able to see that. While you have it off it's good to replace the cap and rotor, cam shaft sensor, valve cover gaskets if they are leaking, coolant return hose, and anything else that's hard to reach. Make sure you cover the valley and scrape off the old gasket really well then shop vac it up. I soaked my intake in degreaser like ten times, rinsed it with the hose, and let it dry overnight. Don't use the intake end gaskets my buddy did and he's leaking oil again. Use a good RTV like Permatex or Right Stuff and lay a thick bead in place of them. Let it cure for about half hour before installing the intake. It's easy but takes a long time. I also replaced the coolant output pipe that bolts to the intake. Mine was nasty.
Sounds like I'm in fairly deep... Maybe I'll order everything I need and take a few days off work when it arrives. Any specific reason for replacing the cam sensor? And I don't believe my valve covers are leaking, but how would I tell?
I'll run octane booster to stop the detonation until I can afford to do all this work. If I'm doing the cap and rotor, might as well get new plugs and wires too, right? It's in the future plans anyway...
Thanks for your help I'm guessing most, if not all of these parts, can be purchased through Kolak? He seems to have everything.


Quote:
Originally Posted by HighLonesome View Post
Weld an aluminum plenum plate to the intake manifold and never worry about it again is my advice. I can't do that with my older ZJs due to the EGR ports. They clog and the only way to clear them is remove the plenum plate and ream. You needn't worry about such limitations.
I've done very little welding in my life (a few times in shop class in high school, that's all) so that's unfortunately not doable for me. Thanks for the suggestion though!


The list so far:
- plenum pan & gasket
- cap, rotor, plugs and wires
- camshaft sensor (?)

Anything I'm missing?

Thanks again!

edit: oh yeah, another question I forgot: since it was overheated a couple times, would seafoaming both the crankcase and the upper engine be a good idea? I'd imagine the heat cooked in a decent amount of crap.

I'll take a look at the hughes kit, thanks
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post #6 of 29 Old 09-04-2012, 02:07 PM
PolkaPower
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It's much easier to do with all that out of the way, plugs wires ect. The Cam sensor is a round flat sensor that sits right beneath the cap and rotor. If it goes out once you turn your Jeep off it won't start again. That's why I replaced it just for insurance. I took two days to complete just because I spent a long time cleaning and then I had to let the intake dry. You are also going to need the vacuum hoses most likely because they will be brittle and break on you when you try to remove them.
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post #7 of 29 Old 09-04-2012, 02:17 PM Thread Starter
B93
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Okay, I'll keep that in mind about the cam sensor. I may not replace it though, money's pretty tight...
Thanks for the tip about the vacuum hoses. Do you think smearing some vaseline (the petroleum jelly) on them and letting it soak would help? Or will that just leave me with greasy hoses?

I'm off to work, but I'll be back tonight or tomorrow. Thanks for all the help, I love this forum
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post #8 of 29 Old 09-04-2012, 02:18 PM
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No you will have to get new hoses if they are hard and brittle.
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post #9 of 29 Old 09-04-2012, 02:25 PM
errorcode3
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once you start in on this, i would recommend you having another car available. You can run into alot of little issues as you plod along. Remember you could be the first person ever on your jeep removing some of the bolts, they can break/strip. And the same goes for the hoses, be prepared to break one and have to run to napa/orielly's (whatever your fancy) to get new parts. and some may have to be shipped in, like the intake manifold bolts (but now the hughes kit comes with them).

98 - Slate 5.niner. minor mods
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post #10 of 29 Old 09-04-2012, 02:26 PM
PolkaPower
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Orellys had the intake manifold bolts. They were felpro. Just be gentle removing the bolts. All mine came out fine but then again I don't live in the rust belt.
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post #11 of 29 Old 09-04-2012, 02:31 PM
errorcode3
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i had the front two manifold bolts break off in the block, that hole they sit in is a very stupid idea. so i filled them completely with RTV and rammed the bolt in there. problem solved..i hope..and no where in town had them, so i had to wait 2 days to get them.

98 - Slate 5.niner. minor mods
02 - Silver Liberty (wives mall crawler)
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post #12 of 29 Old 09-04-2012, 02:40 PM
PolkaPower
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Quote:
Originally Posted by errorcode3 View Post
i had the front two manifold bolts break off in the block, that hole they sit in is a very stupid idea. so i filled them completely with RTV and rammed the bolt in there. problem solved..i hope..and no where in town had them, so i had to wait 2 days to get them.
Darn what an ordeal. I bet a few choice words are still echoing in that garage.
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post #13 of 29 Old 09-04-2012, 02:48 PM
errorcode3
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all i know is the jeep was lucky its a 5.9, otherwise i would have beat her like she owed me money..
but i suppose a 408/426 stroker build based on two stripped bolts may have been fun..
sorry to wander off topic..i get distracted..ohh something shiny..

98 - Slate 5.niner. minor mods
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post #14 of 29 Old 09-04-2012, 03:08 PM
HighLonesome
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Quote:
Originally Posted by B93 View Post
I've done very little welding in my life (a few times in shop class in high school, that's all) so that's unfortunately not doable for me. Thanks for the suggestion though!
I can't weld either. Never have. I'd have a shop TIG it.
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post #15 of 29 Old 09-04-2012, 04:55 PM
PolkaPower
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Be careful with your ac lines. When I moved the alternator and compressor as one unit on the bracket it exposed a weak spot in the ac hose. Now I have no ac temporarily.
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