Plenum Pull: problems and questions

[ammrpm]

Well it seems the farther I get into this plenum pull the more questions I have. I have now got the injectors and one of the I/H off.

A little background on my car: 93 with 15k miles. Has been driven less than 1K in last 10 years.

Here is a shot of the injectors. Do these look ok? Or need replacement? Keep in mind not all of the injectors look like this. This was the worst pair.



Once I got the I/H off on the drivers side I noticed a lot of oil on the gasket material. Is this just there because it came out when I broke the seal on the gasket? Or was it seeping oil around the gasket? Could this be part of the reason I see alot of oil staining in the runners? It definitely looks like the gasket was starting to fail near the water jacket. See pictures below:






One other problem I have encountered now... I have broken a bolt head off on the coolant outlet pipe that threads into the I/H. Any suggestions on how to get this broken bolt out? I have actually broken one on both the drivers side and passenger side coolant outlet pipe.




Thanks for all the help!

Aaron

[lakemeadzmonster]

That broken bolt get problem:

get a real good penetrate like Yield and work it into the bolt and also around the edges of the pipe seal,

if I'm looking at it right the threads are not holding it together, tap on it and it should loosen, once you get the pipe off the soak the threads and loosen up the stud.

[bdw18_123]

On the injectors: If the car was running good, they are probably fine. Since your Z is a '93, they should be fine with the ethanol in the gas. But the 90-92 ZR-1 stock injectors WILL fail prematurely with today's gas blends. However, you do need to at least clean them up real good. That's what happens when you only drive your car 1K miles in 10 years.

On the gaskets: It does look like the oil on the gasket is probably just from from that oil that you can see that is sitting in that cupped area. Not a big deal I don't think. You do need new gaskets though; like you noticed already, looks like that one area on the gasket is coming apart/failing.

The oil staining in the runners is a common occurrence with the LT5 because of the amount of oil that goes into the plenum from the PCV system. This is why a lot of guys install the catch can to prevent that oil from getting into the plenum. There is always more in the secondaries as you can see because a lot of people don't drive their Z's hard enough to open the secondaries, so the oil gets backed up in there a bit. Mine were even worse than yours. That's why you want to make sure that you get a good high RPM blast at least once or twice every time you drive it to clean out the secondaries.

Another way to keep the secondaries clean is a trick where you get the secondaries to stay open while your driving on the freeway so they can get cleaned out by the fuel. What you do is floor the gas pedal for a few seconds, then release the pedal about to about 95% of the way up. The secondaries will stay open as your driving for as long as you don't let the pedal all the way up. I think I'm remembering this process correctly, someone correct me if I've got it wrong.

On the broken bolts in the coolant pipes: You will have to get the coolant pipe off of the busted bolt to be able to get to it. I ran into the exact same problem with my '90 ZR-1, it's a fairly common issue. Spray some penetrating oil on it to loosen the rust and let it soak. Then try to work at pulling the coolant pipe off, you might have to figure out a way to pry on it (without damaging it) to gain some leverage to get it off. Once the pipe is off, spray some more penetrating oil around where the bolt enters the IH. Then get some vise grips and try to twist out the broken stud. If it is really rusted in there, you might have to get a machine shop to remove it.

I had to get two of the broken cam bolt studs on my heads removed by some sort of electrolysis or something by a machine shop, they disintegrated the bolt with electricity somehow. They were really stuck in there.

[tomtom72]

I'm no expert, but a lot of what is getting oil staining I actually think is a combo of oil and gas. The other pictures in the other thread before you got to showing us the injectors, looked a lot like gas leaking from gummed up injectors.

Now that I see your "worst two" injectors I say at least 50% of the staining is from gummed up injectors. The car was not driven enough, the secondaries were not opened enough to keep everything clean.

Jerry, jerrygaskets.com, has spare water tube bolts for you or you could get the s/s kit from Jerry also. Soak the heck out of that water tube with some rust chemical of your choice. There are no threads in the water tube box, only in the I/H. Soaked enough it should be able to be pried apart so you can expose the bolt. I would use some rust spray and maybe some heat from a MAAP gas torch to help it along. Or, just the rust spray and tap it to vibrate the liquid down the threads, a vice grip or a stud extractor, and it should come out. You know the drill? Back & forth, don't just try to turn it out one shot.

Oh, forgot Jerry has the gaskets also. Yours looks like some one pried with a screw driver, the tears and yes the edge at the water passage does look to be failing. I'll ask this, were all the I/H bolts tight? Did they give that "snap" when they yielded. On my car all of those bolts were barely 10 n/m...I could almost do them by hand, and the CCV box cover bolts! Jez what a mess under my plenum. Nothing was tight!


Tom

[ammrpm]

Thanks for the responses!

I just bought this car about 2 months ago. I knew it had a vacuum leak under the plenum when I bought it so I knew I was going to pull the plenum after I got it.

It seems the lack of driving this car has caused its fair share of problems. So I am going to go ahead and replace the injectors, coils and plug wires while I have the plenum off. I will probably go ahead and have the plenum and I/H ported as well.

I am definitely going to give Jerry's gaskets some business. I will need lots of gaskets and seals for the plenum, I/H, coolant pipe, injectors. Looks like I will need some coolant pipe bolts as well.

As for the tightness of the bolts on the I/H... not all of them seemed that tight. This might have been part of the problem.

Now that the plenum is off I have been trying to run down the cause of the vacuum leak. I have hooked up my vacuum tool to the secondary vacuum reservoir. The reservoir won't hold a vacuum. It is not a quick drop on the gauge, but it does drop. I also checked the secondary control solenoid switch and it does the same thing, slow drop of vacuum. I checked the secondary actuators and those are both rock steady. They start to crack open at about 1 inhg and are fully open by 7 or 8. Does that sound right?

Where is a good source to find a secondary vacuum reservoir? Where can I find a secondary control solenoid?

Thanks!
Aaron

[jrd1990zr1]

Originally Posted by ammrpm

Thanks for the responses!

I just bought this car about 2 months ago. I knew it had a vacuum leak under the plenum when I bought it so I knew I was going to pull the plenum after I got it.

It seems the lack of driving this car has caused its fair share of problems. So I am going to go ahead and replace the injectors, coils and plug wires while I have the plenum off. I will probably go ahead and have the plenum and I/H ported as well.

I am definitely going to give Jerry's gaskets some business. I will need lots of gaskets and seals for the plenum, I/H, coolant pipe, injectors. Looks like I will need some coolant pipe bolts as well.

As for the tightness of the bolts on the I/H... not all of them seemed that tight. This might have been part of the problem.

Now that the plenum is off I have been trying to run down the cause of the vacuum leak. I have hooked up my vacuum tool to the secondary vacuum reservoir. The reservoir won't hold a vacuum. It is not a quick drop on the gauge, but it does drop. I also checked the secondary control solenoid switch and it does the same thing, slow drop of vacuum. I checked the secondary actuators and those are both rock steady. They start to crack open at about 1 inhg and are fully open by 7 or 8. Does that sound right?

Where is a good source to find a secondary vacuum reservoir? Where can I find a secondary control solenoid?

Thanks!
Aaron

For the secondary reservoir if Jerry doesn't have one there is one on E-bay item # 250785691792.

Secondary control solenoids come up from time to time too. If Jerry doesn't have one and you can't wait try Kurt White.

[rhipsher]

Hey Aron. The ones on my 90 were so bad I just had to slap them on the mill and mill them out. There was no penetrant in the world that was going to get them out. Then I fly cut them and resurfaced the inlets. The finish I machined them to was a 32 which is far better than it really needs to be. I'll call you man.

[mike100]

wow, your adventure mostly mirrors the work I just completed on my 91.

- yes I had the oil pooled up in the vent casting areas.
-yes the water outlet hardware wouldn't unscrew (3 of them)
- yes my injectors were bad (90-92 and modern gasoline issues)
-I had a lot less gunk in my ports (car had 26k miles when I bought it).
-the vacuum leak was the reason I got into it, and on mine, it was one of the large hoses that go to the purge solenoid just ahead of the coils- either one may pop out. the car idles below 1000 rpms all the time after I fixed that. Go ahead and introduce your self to all the vacuum circuits with your vac pump-it's good to know what it is all for.

I ported mine- it feels a lot better on the freeway over 5000 rpm now, but i can tell you the 405hp engine has a lot better ports than the 375 hp cars from the pics you put up.

btw, the injectors look bad- maybe you should send them out for flow testing/cleaning.

also, I found some metric cap screws at the hardware store for 25 cents a pop to replace the water outlet hardware. I drilled the head off the bad screws which left the shaft to which I just grabbed with vice grips and unscrewed.

[tomtom72]

Hi Aron, First thanks for not taking my post the wrong way. I was not trying to sound like a know it all.

Jerry may have a tank for you. If not, which I doubt that he doesn't, you proly can repair the cracks as the seams open up as the plastic dries with age. Just slap some epoxy on the thing & give it a shot to see if that solves the problem of leakage. Check it like you would check a tire,submerge it with air in it...you know that drill.

On the solenoid make sure that you are blocking off the vent securely when you test it. Usually if the solenoid has an issue it will set a DTC. If you had no DTC's, then I would redo the vacuum test on the solenoid again just to make sure.......although I r&r'ed mine just because of age... There is a trick to testing it though because one of the three ports is an air intake and it has to be closed to get a valid vacuum test result. I wish I could be more specific from memory but I did this stuff back in 05 and I don't remember....senile I guess! If you run into an issue with it, post up and I'll dig out my spares and test one so I can relate the proper procedure to you.

The secondary actuators have passed the vacuum test with flying colors. Just one more thing on them. Redo the test and watch the movement of the arms that they move smoothly as they actuate the linkage to the butterflies and watch all that stuff to see smooth movement, ya'll hear? You're doing okay, when you're dunn you get to be a plenum pull member!

I can't remember your car is a 405 hp car, right? If so you can have your injectors cleaned. The later, after 91, injectors do not fail due to alcohol in the gas. I don't know what the money difference would be cleaning vs new....but it's an option for you.


Tom

[Coupe89]

Coolant outlet pipe.
I drill out the studs, I did 4 of them.
Then sent the pipes to Carter