5.0L Intake Plenum

I have a 1998 GMC Sierra SLE ext. cab 4x4 with 5.0L (with 197K miles) that is leaking (severely) from the intake plenum. By severely I mean as soon as you pour anti-freeze in the radiator, it comes flowing out the top and down the back of the engine. I had a coworker who is more of a mechanic than I look at it, and he said it's the Plenum. Some of my questions is:

How difficult is this for a shade tree mechanic like myself to do?

Will I need special tools to replace the plenum?

What other items will I need other than a new plenum, and gasket set? (I plan to change the thermostat since I'm there already)

What can I expect to find with the lower 1/2? Will it need to be replaced/repaired?

What else should I check on?

This truck has been a good truck to me. And I do the basic routine maintanence. I figure, treat her right-and she'll treat me right!

Thanks in advance for any help/advice!


(I did a search for this problem-but came up empty. I heard this was a fairly common issue. Could be my search words weren't right)

If the pleanum is that far gone which is not uncommon I would go the little extra and do the lower intake gaskets also. Would be terrible to get all that together and pop a lower gasket that is just as old as the leaking pleanum.

Good point about replacing the lower gaskets as well. I got a price from "my" mechanic of $200 for just the labor portion of this job. Not sure I want to attempt this or let someone else have the headache. Why am I hesitant? Every time I work on something, it never fails that I accidentally break something, and in my fit of rage of breaking something I end up breaking something else. I also tend to use every swearword I know, and make up a few along the way. None of this is good for my blood pressure. :biggrin:

However keep the tips and advice coming....

If truck currently takes orange or dexcool antifreeze, I would recommend changing it to yellow or green after changing intake gaskets. Dexcool has been known to eat gaskets. Just do a flush and fill.

If truck currently takes orange or dexcool antifreeze, I would recommend changing it to yellow or green after changing intake gaskets. Dexcool has been known to eat gaskets. Just do a flush and fill.

I was wondering if I could do that. I think the green is cheaper too. And almost any gas stations seem to carry the green "Good for all vehicles" stuff vs the Dexcool. Thanks for the advice!

PS-like your name, could be I'm biased as my daughter's name is Kelsey too. :iceslolan

I used yellow antifreeze, cause if you dont get all the orange out, the yellow will mix with orange. Im sure the green will mix as well. I flushed mine 2-3 times to get all of that orange junk out. My last name is Kelsey. I get that alot. Thanks and good luck.

One more thing, not sure if you have down the intake gasket yet, but its fairly straight forward. I do all my own work on my cars, and it wasnt hard. It took about 4-6 hours. Good luck

I was told to get a metal intake plenum. Yet all I can find is a metal lower-not the upper (plenum). Too bad someone like Edelbrock doesn't make a one piece intake manifold for this model. I like the vortec and the power it has, but who doesn't want "more power"?! :naughty:

So far this is my list:

Intake Plenum
Intake Plenum Gasket Kit
Valve Cover Gaskets
Oil
Oil Filter
Antifreeze (yellow or green)
Lower Intake Gasket Kit
Thermostat
Thermostat Gasket


What else am I missing?

?Torque Wrench? (I don't own one-good excuse for one)
I assume the bolts need to be torqued specifically?

?Intake Manifold Bolts?
Should they be replaced? I see them in catalogs and wondered....

They actually dont make a metal plentum gasket. They make the lower intake manifold gasket in metal though. You dont need a metal one unless you arent going to drain the dexcool antifreeze. Because as I said before, dexcool has been known to eat gaskets, but its up to you. For piece of mind I would get the metal one, but oem gasket is alot cheaper. Your list is excellent. If intake has been leaking bad I would change your plugs as well. Because the intake leaking bad, would actually cause the antifreeze to get to your plugs and cause a miss and them to burn hot. I dont remember if you had those one your list. Also if you dont have a flush and fill kit, I would recommend that as well. Good luck

I plan to do this next weekend. I just ordered the parts and should have them in a few days (with the holiday weekend). I'm hoping to get a friend to help out. If it took you 4-6 hours, I better set aside about 10-12 hours! I'll have to order a pizza in there somewhere too! haha. I do appreciate all the help. I'll admit I'm kind of nervous with this one. But then it's something new to me-that is the reaction I always have with something new.

Well I got it fixed. Ok, I didn't do it due to various reasons. So I had "my" mechanic do it. It ended up being the intake gaskets that failed. Apparently the previous owner had this very same issue. And I'm guessing they worked for permatex as there was alot of it used! :nono:

The mechanic looked everything over-I told him I don't want to see him again, That while I appreciate his expertise, the quality work and the no bs assessments, we have to stop meeting like this. He agreed. Until next time that is.

The antifreeze has been changed out to the green stuff. Valve cover gaskets, both intake gaskets, antifreeze, oil & filter have all been changed. I was impressed with the amount of power I suddenly gained as I drove it home. He also suggested JD injector cleaner-they were cruddy. The plenum was just fine, not warped or anything. So I will be putting that up on ebay shortly. There was some other things he did that I cannot remember at the moment. All this for $200.00 labor! :biggrin: I supplied the parts-saves a lil money there. Anyhow thanks for the advice and help!