Plenum Pull Q's

[tomtom72]

Hi guys,

I should know this but I'm old & senile & I forgot!:redface:

If you have to pull the plenum you should wait for the motor to be stone cold, right????

I know it's a stupid Q. I rent a garage to keep my Z and I have to drive to it to do any work on the car. It's not that far but by the time I get there I'm about 1/2 way on the temp gauge. So I'm thinking that I should not work on her till the coolant is cold to the touch, right???:icon_scra

Thanks,
Tom

[cuisinartvette]

I feel your pain, I have to drive across town to a garage I keep mine at too. What a PITA if you forget tools....Guess thats why mine has sat for so long.

Id drain some coolant from the pitcock on the radiator before pulling it off. Plenum will be warm to the touch for a bit.

[Aurora40]

I'd think it would be more for your sake than the cars, though. I imagine you could pull it off warm and it would be fine, if your hands can stand it.

Why do you have to go under there again?

[tomtom72]

Thanks Ron & Bob! I seemed to think I remembered an old time wrench telling me never to dis-assemble a hot motor????

Ron, I feel your pain. We should start a club for homeless ZR-1's. Forgetting tools is the least of my problems. My Z is my only car now so if I don't bring it, it don't get dunn!

Bob, I got a SES light the other day & it turned out to be 61, 2* trouble. My scanner will not do all the tests that a Tech1A does so I had no choice but to do the flow chart without doing the required functional test. And.....after all that it turned out to be the ECM!:mad:

Well at least I passed my refresher course on plenums 101....it was easier the second time around! But I look on the bright side, at least I confirmed that my CCVB cover no longer leaks!:mrgreen:

Well time for a shower & a good test drive.....it's a good thing that I have bad luck with vettes & keep a small cashe of spare parts!:sign10:

:cheers:
Tom

[tomtom72]

Test drive report:




:mrgreen: I now have a vette again, not some car that just looks like a vette!:mrgreen:

[Jeffvette]

Tom, keep in mind all the pieces are aluminium and they get a little softer when warm.

[Norsky4360]

I'd wait until it has cooled down enough for the coolant pressure to be almost gone. Then crack the expansion tank cap to relieve the rest of the pressure.

When I was doing my 'very last first' plenum pull someone shared a tip to drain the coolant from the expansion tank rather than drain everything via the radiator. Naturally I saw that after I'd already drained the radiator. I'll have to dig a little to find it.

[tomtom72]

Thanks guys. Yea what I did was some other stuff that was bothering me and by the time I was dunn there was no psi left in the coolant sys. & the coolant was just barely warm to the touch. Man these motors retain heat for awhile!

Jeff, I should remember that for the future! I was thinking that there was a slight chance of having things warp if I started to take stuff apart while still too hot. That's what kills me about the diagnostic charts in the 6E section.
"Scan motor in closed loop, does the scan report 2* vac @ .74v? Yes, pull plenum and test connector @ solenoid by shorting A & B leads."

Some non- trained backyard type like me sees that & thinks "how long do they wait to pull the plenum"? But I fixed the rattle from my front calipers and then tackled the plenum!

I should have swapped the ECM 1st just for sh*ts & giggles and I could have saved the labor. I think I learned something. The rapidity at which the DTC re-set itself should have tipped me to an electrical issue. I would clear it using the scan tool and it wouls re-set within 5 seconds. Oh well.

Hey, do we all know anyone reliable that repairs ECM's????

:cheers:
Tom

[Belsy]

Many years ago a friend pulled his dual quad system off while warm and it warped so bad he could not re-use even after planing the surfaces.
WAIT and enjoy the result!!:sleepy1:

[Belsy]

On this note, what is the concensus on coolant by-pass on plenum & throttle body??

[jrd1990zr1]

I'd wait until it has cooled down enough for the coolant pressure to be almost gone. Then crack the expansion tank cap to relieve the rest of the pressure.

When I was doing my 'very last first' plenum pull someone shared a tip to drain the coolant from the expansion tank rather than drain everything via the radiator. Naturally I saw that after I'd already drained the radiator. I'll have to dig a little to find it.



When I went to Gordon's school last year he pulled the expansion tank loose drained some coolant and left it lower than the plenum. Seemed to be the quickest way too get the coolant below the plenum.

[Jeffvette]

Quickest way is to get a sucker. One of the better tools to have as it helps in changing rear diff fluid and sucking fluid out of hard to reach pockets.

[GOLDCYLON]

On this note, what is the concensus on coolant by-pass on plenum & throttle body??

I have it, Live in Arizona, no issues and keeps the ZF.Doc (My tuner) happy :mrgreen:

[tomtom72]

Okay since this is my thread I would like to mention a few things for the first time plenum puller to observe:

1. Remember that the motor should be cooled off before dis-assembly. It will be warm to the hand, so check the coolant. If you can detect any heat enough to do harm to skin, stop & wait.

2. Draining the radiator thru the pet-**** is okay but if you are removing the I/H's be aware that the coolant level will be still in the heads. It's okay but be careful, or just open the T-stat housing & get it all.

3. On the 90's the fuel block at the rear right of the plenum has the inner fuel line in the way of that plenum bolt. There three screws, torx T45(?), you need to loosen two of them to swivel the line next to the boly out of the way to get on that plenum bolt squarely. I expect that this might apply to all of our set-ups. You can remove the lines entirely as new O-rings come in the top end set & if you're doing injectors you must do that. Oh, bleed the schrader first!

4. If it's really your first time use the blue painter's tape to label all the electrical connections and hoses. If ya got a digital camera use it! Or you could just label all the connectors with a sharpie. Point is the first coupla times there is a lot of stuff & a little cheat sheet will pay back big time.

5. The bag & tag thing will help alot if you're going down to the valley floor to do housekeeping. There is a lotta stuff under there so go slow the first few times because it all goes back....no parts left over!

6. Don't yank the plenum till ya got all the vac lines & DIS connections off!
For the 90's there are three vac lines on the T/B: the double left side one, one under @ the right side ya can't see till you lift the front of the plenum about four inches. The two center high vac lines, L & R, the MAP, Regulator, P/Booster, PCV top connector. The two T/cables, IAC, IAT, TPS, Two front DIS connectors, one rear DIS main harness connector has a 7 or 8 mm bolt holding it on & ya get that after ya r&r the MAP bracket + MAP and the lower PCV hose w/PCV's or ya can't see the bolt let alone get on it from the trans tunnel. You get all that stuff & now ya can lift the plenum off of the I/H's.

At this point ya can pretty much do everything like starter, coils & wires, injectors, 2* throttle system parts, clean the oil in the valley & evict the mouse & spyders (dead ones for those of us that DD the car:mrgreen: ), about the only thing ya can't do is the gasket for the CCVbox cover. That requires more r&r of stuff. Oh, also consider that the A/C system's vac check valve is the big check valve under there along with the two temp senders in the left I/H. The box cover hoses can be dunn also if they are bad. I can't remember if the A/C & Alt are in the way of just doing all the stuff save the CCVB gasket....I did r&r them when I did my box cover gasket along with the shield & 2* t-linkages...of that I'm sure. You'll see when ya get there as it is obvious once ya get all the stuff on top of the CCVB out of the way.

Anyway, I hope this might help anyone who has to do this the first time. Go slow & take notes. It is more intimidating than it is difficult. You do it once & ya got this pretty much beat...ya do it twice and you will wonder why ya thought it was so hard. Familiarity makes it straight forward.

:cheers:
Tom

[Aurora40]

5. The bag & tag thing will help alot if you're going down to the valley floor to do housekeeping. There is a lotta stuff under there so go slow the first few times because it all goes back....no parts left over!
FWIW, what I do is just take a piece of printer paper, and draw on it a quick sketch of the piece. Then I stick the screws through the paper where they line up on the piece. It's quick and easy and works great.

[Jeffvette]

5. The bag & tag thing will help alot if you're going down to the valley floor to do housekeeping. There is a lotta stuff under there so go slow the first few times because it all goes back....no parts left over!

Bag and tag, what is that. I throw everything into a single box!


Two front DIS connectors, one rear DIS main harness connector has a 7 or 8 mm bolt holding it on

It's a 1/4" bolt that holds the main DIS connector on. The other smaller 2 wire one is the connector for the crank sensor signal.


you get that after you r&r the MAP bracket + MAP and the lower PCV hose w/PCV's or ya can't see the bolt let alone get on it from the trans tunnel. You get all that stuff & now ya can lift the plenum off of the I/H's.

You can actually access the MAP sensor wire and vacuum tube before you get this far. You can squeeze your hand behind the plenum on the drivers side and undo all of these.

about the only thing ya can't do is the gasket for the CCVbox cover. That requires more r&r of stuff.

You can get the breather box off with out removing the injector housings. It is very tight, but can be done. You must have the starter and the coil packs out of the way though.


Good write up Tom.

[tomtom72]

Thanks Jeff!

Now class pay attention, that includes me also:o , to what corrections Jeff made. I get a D- on the written part of my exam.....however, since the end result on the practical part of my exam is that I now have a ZR-1 again and not some car that just looks like a ZR-1, I get a passing grade of "good".:mrgreen:

I would also urge any first time plenum pullers to check out the Pacific Northwest home page for the skinny. Also the Texas chapter's(Big Country Corvettes) home page and Corvette Action Center's ZR-1 section for a complete and accurate step by step on this task.

:cheers:
Tom

[A26B]

You can get the breather box off with out removing the injector housings. It is very tight, but can be done. You must have the starter and the coil packs out of the way though.

Coil pack base yes, starter no.