Vacuum leak

[MuRCieLaGo]

Hi,

My '91 ZR-1 got a vacuum leak. Key on, the vacuum pump turns on every seconds or so.

-Blocked the vacuum port directly on the pump - stops running (so the pump is fine).
-PCV valve was loose so I fixed it by installing vinyl sleeves.
-I tightened a lot of hoses - most of them were loose.

I'm very afraid of pulling the plenum now. Especially because I don't want to spread antifreeze everywhere.

Can I say goodbye to my vacuum problem if I remove the secondary system? If I do so, I will order a chip from Haibeck. Will I be able to switch to normal mode or I will be locked to Full Power?

[Dynomite]

Hi,

My '91 ZR-1 got a vacuum leak. Key on, the vacuum pump turns on every seconds or so.

-Blocked the vacuum port directly on the pump - stops running (so the pump is fine).
-PCV valve was loose so I fixed it by installing vinyl sleeves.
-I tightened a lot of hoses - most of them were loose.

I'm very afraid of pulling the plenum now. Especially because I don't want to spread antifreeze everywhere.

Can I say goodbye to my vacuum problem if I remove the secondary system? If I do so, I will order a chip from Haibeck. Will I be able to switch to normal mode or I will be locked to Full Power?

Finding A Vacuum Leak (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-7.html#post1584987830)

Full power all the time with secondaries removed. I would just remove the plenum (block TB Coolant when you are there) and find/fix the vacuum leak. Just drain a gallon or so of coolant and remove the Plenum.

Removing Plenum (including the 10 minute Plenum Removal) (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-4.html#post1581663365)

Injector Housing TB Coolant Blocking (http://www.corvetteforum.com/forums/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-10.html#post1588695506)

You can also Block TB Coolant without removing the Injector Housings but do have to remove the two Injector Housing Coolant Manifolds just to keep the aluminum shavings out of the coolant system.

Here we go again....if you do remove the Plenum....might as well remove the Ignition Coils and starter. You can then recondition the Starter Solenoid......and clean the Valley Drain.

[MuRCieLaGo]

Thanks Dynomite,

Is there any trick about that coolant thingy? Where is the drain bolt?

[Dynomite]

Bottom passenger side you can reach and feel it.....use a pliers and you can open it (unscrew it)

Radiator Drain (http://www.zr1.net/forum/showthread.php?p=128579)

[MuRCieLaGo]

At first I unscrewed what appeared to be the oil cooler drain plug. Am I right assuming it was oil from the oil cooler? It is not far from the radiator drain plug.

[Dynomite]

At first I unscrewed what appeared to be the oil cooler drain plug. Am I right assuming it was oil from the oil cooler? It is not far from the radiator drain plug.

Yes.....you drained your oil cooler? ;)

Oh...well.....no harm and no foul.......just ad a couple quarts of oil to replenish what you drained out of the oil cooler.

[MuRCieLaGo]

Now I've got an oil leak from this oil cooler drain plug. Oh well, what a bad day.

If I continue tightening, the plug will finish in the oil cooler. I removed the drain plug and the threads seem to be perfect. Do I need to put some kind of Loctite?

[MuRCieLaGo]

I really need help on that one guys... The threads are neverending I really am confused now.

[MuRCieLaGo]

There you go: drain plug is now inside the oil cooler.

[Dynomite]

Now I've got an oil leak from this oil cooler drain plug. Oh well, what a bad day.

If I continue tightening, the plug will finish in the oil cooler. I removed the drain plug and the threads seem to be perfect. Do I need to put some kind of Loctite?

Be very careful....I have seen some discussion about that plug being a tapered pipe thread. I use permatex thread sealant on all pipe threads.

[secondchance]

Sorry to hear of your predicament.

I didn't even know the oil cooler has a drain plug. Are the drain plugs on 90 - 92 model year coolers only? I had my oil cooler out and flushed it out with mineral spirit but didn't notice any plug.

Ebay has a used 90-92 oil cooler plus AC condenser for sale.
http://www.ebay.com/itm/90-91-92-CORVETTE-C4-ZR1-oem-engine-oil-cooler-and-ac-a-c-hvac-condensor-/141698642788?hash=item20fde5b364:g:qNAAAOxyAs9SPMo P&vxp=mtr

Also, a new one but listed as for 93-95 ZR-1.
http://www.ebay.com/itm/94-95-C4-CORVETTE-ZR1-LT5-ENGINE-OIL-COOLER-NEW-NOS-GM-10219643-ZR-1-/231158079394?hash=item35d2185fa2:m:mEcAyaqN8L3ORM6 yPUkygPw&vxp=mtr

Does anyone know what the difference is? If it's just bolt hole location, I would buy a new one for later years and modify as needed.

[Dynomite]

I didn't even know the oil cooler has a drain plug. Are the drain plugs on 90 - 92 model year coolers only? I had my oil cooler out and flushed it out with mineral spirit but didn't notice any plug.



I think that Oil Cooler Plug is only on the 90'-92'. And as WVZR-1 suggests it is likely an NPT (which is a tapered thread). And someone said (I forgot where) that it is the same as the Drain Plug provided by Corvette Central for the Differential.

I believe the "conventional wisdom" needs to prevail here because the plug the OP mentions isn't meant to be a "service port". I don't know the thread size involved here but for any thing other than maybe it's use to drain the oil for a cooler change seems maybe foolish. Any conventional engine oil drain plug uses a gasket or seal to prevent seepage and I'm quite sure this could only be some sort of an NPT plug and that's not a conventional method used for engine oil service ports.

[secondchance]

Learned something new today. Mine being a 94 explains why I didn't notice even with the cooler out of the car.

[MuRCieLaGo]

Sorry to hear of your predicament.

I didn't even know the oil cooler has a drain plug. Are the drain plugs on 90 - 92 model year coolers only? I had my oil cooler out and flushed it out with mineral spirit but didn't notice any plug.

Ebay has a used 90-92 oil cooler plus AC condenser for sale.
http://www.ebay.com/itm/90-91-92-CORVETTE-C4-ZR1-oem-engine-oil-cooler-and-ac-a-c-hvac-condensor-/141698642788?hash=item20fde5b364:g:qNAAAOxyAs9SPMo P&vxp=mtr

Also, a new one but listed as for 93-95 ZR-1.
http://www.ebay.com/itm/94-95-C4-CORVETTE-ZR1-LT5-ENGINE-OIL-COOLER-NEW-NOS-GM-10219643-ZR-1-/231158079394?hash=item35d2185fa2:m:mEcAyaqN8L3ORM6 yPUkygPw&vxp=mtr

Does anyone know what the difference is? If it's just bolt hole location, I would buy a new one for later years and modify as needed.

That used one is $350 shipped in Canada. I hope I can fix it by simply installing a bigger drain plug there. Or I can always ask a local shop to weld over the plug, you think it would be a good idea?

At the moment I'm trying to remove the radiator, big pain in the *** to remove the 7mm bolts especially driver side!

[Dynomite]

That used one is $350 shipped in Canada. I hope I can fix it by simply installing a bigger drain plug there. Or I can always ask a local shop to weld over the plug, you think it would be a good idea?

At the moment I'm trying to remove the radiator, big pain in the *** to remove the 7mm bolts especially driver side!

Replace only the bottom 7mm.

To remove the radiator housing, disconnect the Oil Cooler lines manifold (one bolt in the center). You can then squeeze/bend/pry the radiator housing up (drivers side first) and out.

There are a couple bolts each side that have to be removed from the chassis frame rail. And.....maybe electrical connectors that are obvious and fan housing disconnected (bolts top and bottom) and the Dryer mounting disconnected from radiator housing.

[Dynomite]

There you go: drain plug is now inside the oil cooler.


The cooler uses the same plug as the rear differential drill/drain kit that CorvetteCentral has. I bet it could be screwed in too far and be stuck inside the cooler. As far as not being a service port, the FSM gives oil refill quantities if you drain the block, block and filter, block and oil cooler, block and cooler and filter, and engine overhaul.



Yes......apparently the Oil Cooler Drain Plug is like the Differential Drain Plug provided by Corvette Central.

[MuRCieLaGo]

Yes......apparently the Oil Cooler Drain Plug is like the Differential Drain Plug provided by Corvette Central.

When the cooler will be in my hands I'll be able to remove the drain plug stuck inside but it's leaking, threads in the cooler seem to be worn.

[Dynomite]

When the cooler will be in my hands I'll be able to remove the drain plug stuck inside but it's leaking, threads in the cooler seem to be worn.

If it is leaking the female thread in the Oil Cooler could be cracked which would also make it possible to screw the plug in further than normal.

I have never removed the Oil Cooler Plug for any reason. Some others have actually drained their Oil Cooler Oil during an Oil Change which I also do not do.

[MuRCieLaGo]

If it is leaking the female thread in the Oil Cooler could be cracked which would also make it possible to screw the plug in further than normal.

I have never removed the Oil Cooler Plug for any reason. Some others have actually drained their Oil Cooler Oil during an Oil Change which I also do not do.

I hope it is only leaking from the threads... How I am supposed to sleep tonight?

[Dynomite]

I hope it is only leaking from the threads... How I am supposed to sleep tonight?

I think you can pick up a good used Oil Cooler that will not break the bank. ZRXMAX may have one or know where to get one.....just in case.

[MuRCieLaGo]

I think you can pick up a good used Oil Cooler that will not break the bank. ZRXMAX may have one or know where to get one.....just in case.

I don't want to be that cheap guy but I'm pretty sure I won't need to change my whole oil cooler only because of stripped threads.

Plan A: Try to put a conventional drain plug there (with a washer).
Plan B: Tap bigger threads with a bigger drain plug.
Plan C: If it is cracked, I'll have a plate welded under the oil cooler.
Plan D: If the oil cooler really is broken, alright I'll look for a used one.

But thanks Dynomite I really appreciate your help!

[Dynomite]

I don't want to be that cheap guy but I'm pretty sure I won't need to change my whole oil cooler only because of stripped threads.

Plan A: Try to put a conventional drain plug there (with a washer).
Plan B: Tap bigger threads with a bigger drain plug.
Plan C: If it is cracked, I'll have a plate welded under the oil cooler.
Plan D: If the oil cooler really is broken, alright I'll look for a used one.

But thanks Dynomite I really appreciate your help!

I like your Plan A.
If it is originally an NPT or Pipe thread it would be relatively easy to find a slightly larger straight thread for which you can drill and tap and then use a bonded washer like for the Oil Pan Drain Plug. You would then have a Real and somewhat Unique Oil Cooler Drain Plug :thumbsup:

Others would then consider that conversion for Draining/Changing Oil Cooler Oil ;)

[WVZR-1]

I don't want to be that cheap guy but I'm pretty sure I won't need to change my whole oil cooler only because of stripped threads.

Plan A: Try to put a conventional drain plug there (with a washer).
Plan B: Tap bigger threads with a bigger drain plug.
Plan C: If it is cracked, I'll have a plate welded under the oil cooler.
Plan D: If the oil cooler really is broken, alright I'll look for a used one.

But thanks Dynomite I really appreciate your help!

I don't think A, B or C rational or practical. I believe you remove the plug and with a "correct device/thread pitch gage" determine what it is that's there and make no "rush to judgment" in repair. I don't believe I'd go to the aggravation of removal until it was determined that I needed to.

Is it magnetic? If it can be determined that it is an NPT product maybe just changing the material used and an appropriate sealer is a more desired repair. Is it maybe NPS? Is it maybe an ISO 7-1 pipe? Is it maybe Metric? It's a "once and done" thing. Identifying the removed plug I'd think critical - no guessing - use thread pitch gage and appropriate measuring devices.

[Dynomite]

I don't think A, B or C rational or practical. I believe you remove the plug and with a "correct device/thread pitch gage" determine what it is that's there and make no "rush to judgment" in repair. I don't believe I'd go to the aggravation of removal until it was determined that I needed to.

Is it magnetic? If it can be determined that it is an NPT product maybe just changing the material used and an appropriate sealer is a more desired repair. Is it maybe NPS? Is it maybe an ISO 7-1 pipe? Is it maybe Metric? It's a "once and done" thing. Identifying the removed plug I'd think critical - no guessing - use thread pitch gage and appropriate measuring devices.

On second thought......I completely concur with WVZR-1.....he is DAMAN. I am not sure if there is enough material or thickness to start drilling/threading for one thing never having even removed said plug. And concur on the removal of the Oil Cooler also. It is pretty easy to try all sorts of sealers for sure depending on the situation.

But if you DO remove the radiator....time to inspect and clean the trash from both the radiator and Oil Cooler...AND....AC Condenser.

[Billy Mild]

I would be worried if you threaded the drain plug all the way in that it will get circulated through the motor and cause a clog somewhere else. Which could cause oil starvation.

Take the cooler out and see if you can get the drain plug to come out of the cooler altogether. Plus with it out, you can make a better repair to it.

Vacuum leaks suck. It seems like everytime I fix mine they come back during the winter time. Not sure what causes that to happen. If you become a member you can actually get the Heart of the Beast magazine. There was a good article about vacuum leaks by Marc Haibeck.

[MuRCieLaGo]

I don't think A, B or C rational or practical. I believe you remove the plug and with a "correct device/thread pitch gage" determine what it is that's there and make no "rush to judgment" in repair. I don't believe I'd go to the aggravation of removal until it was determined that I needed to.

Is it magnetic? If it can be determined that it is an NPT product maybe just changing the material used and an appropriate sealer is a more desired repair. Is it maybe NPS? Is it maybe an ISO 7-1 pipe? Is it maybe Metric? It's a "once and done" thing. Identifying the removed plug I'd think critical - no guessing - use thread pitch gage and appropriate measuring devices.

I had to remove the cooler because the drain plug was stuck inside. I sent it to a local shop to have it welded, I don't see any purpose on that plug, especially because it has NOT an easy access (a beam is in the way).


On second thought......I completely concur with WVZR-1.....he is DAMAN. I am not sure if there is enough material or thickness to start drilling/threading for one thing never having even removed said plug. And concur on the removal of the Oil Cooler also. It is pretty easy to try all sorts of sealers for sure depending on the situation.

But if you DO remove the radiator....time to inspect and clean the trash from both the radiator and Oil Cooler...AND....AC Condenser.


I removed everything but the AC Condenser. It was really dirty there, so I cleaned everything.


I would be worried if you threaded the drain plug all the way in that it will get circulated through the motor and cause a clog somewhere else. Which could cause oil starvation.

Take the cooler out and see if you can get the drain plug to come out of the cooler altogether. Plus with it out, you can make a better repair to it.

Vacuum leaks suck. It seems like everytime I fix mine they come back during the winter time. Not sure what causes that to happen. If you become a member you can actually get the Heart of the Beast magazine. There was a good article about vacuum leaks by Marc Haibeck.

That's exactly why I removed the oil cooler, I wanted to remove that plug from there ASAP.

Kinda sucks to break something while trying to fix a vacuum leak... That's part of the game I guess!

Thanks everyone!

[MuRCieLaGo]

Oil cooler is in place now, started the car this morning. Everything is fine now. The most expensive in that story was the coolant flush. Wasn't ready to pay 94$ for some Prestone.

That vacuum leak will wait now. Enough love given to the car at the moment, time to go back on the RX-7. Much easier.

[weldbead]

hi guys...
havent posted here in months..logged on a few times recently..i got my 94 back in march of '14 ..as the snows melted i realized it had the dreaded constantrunning vacuum pump peterout at 5000 rpm symptoms of leaky vacuum/failing secondaries..immediate solution was buy myself a harley in june of 14 for my wife's birthday..sorry for rambling.. point being here's what i finally did after 11,000 miles on the harley and maybe a thousand on the vette...and the advent of cold weather here in poughkeepsie..i called my local chevy dealer , healey chevrolet..told the service manager i needed an oil change( i had the 3 gallons of amsoil and the wix filter laying around and they agreed to use it),told him about the vacuum leak.. he said they had two techs who had been on vetts for ever..i breathed deep, gave them the car, they fixed it for $600, the vacuum pump runs for 1/2 second and it pulls like hades..
just saying theres that option..enjoy. and good luck..very good luck on tigwelding and tapping the oily threads on the aluminum pan..you could try lampwick on the plug..

[Dynomite]

Plugging the Oil Cooler Drain Plug Permanently (90'-92'-93').

Oil cooler is in place now, started the car this morning. Everything is fine now. The most expensive in that story was the coolant flush. Wasn't ready to pay 94$ for some Prestone. That vacuum leak will wait now. Enough love given to the car at the moment, time to go back on the RX-7. Much easier.

So....just to be clear.....you removed your Oil Cooler and had a local welding shop weld/plug the hole where the Oil Plug Was Located? Or they just welded in the Old Oil Plug? I assume all that or any of that is ALUMINUM Welding?

I had to remove the cooler because the drain plug was stuck inside. I sent it to a local shop to have it welded, I don't see any purpose on that plug, especially because it has NOT an easy access (a beam is in the way).

Anyway.......you did use the Original Green Coolant?

The question often comes up about what is the best coolant for the LT5 engine. I recommend the OE style conventional green coolant. I have found that Dex-Cool causes swelling of the OE LT5 head gasket.

Since it is possible that organic corrosion inhibiter softens the head gasket material, coolant containing organic corrosion protection should not be used in the LT5 engine. The possible values of using organic corrosion protection are small. Dex-Cool claims extended service interval and possible longer water pump seal life. It is not worth taking even a small risk for those benefits since the consequences of head gasket damage are huge.

Use coolant that has the following characteristics:
- Labeled, “For older vehicles.”
- Coolant that is colored green
- Texaco UPC number 76568 12016
- Chevron UPC number 23968 10000
- GM specification 1825M coolant. The current pn is 12378560.
- AutoZone part number 540722. The UPC number is 52948 59081.
- Blue Mountain UPC number 74804 01858

The green coolant might not be available in a brand that you like. However the correct formulation is more important than the brand. Avoid “Universal” coolant. There is no need to compromise when the green coolant is available. Retailers like universal products because they reduce inventory costs, universal coolant is not the best for your LT5, the conventional green coolant is.

For detailed information about my observations of LT5 head gasket swelling see:
http://www.zr1specialist.com/HAT%20Web/articles/evidence%20that%20dexcool%20harms%20the%20cylinder %20head%20gasket.htm

Good For You on the Repairs....appreciate the Feedback :handshak::handshak:

[MuRCieLaGo]

The shop welded the old drain plug in the hole with silver, $40 later.

I used the conventional pre-mixed green Prestone coolant.

http://www.prestone.com/sites/default/p/products/prestone_premixed_longlife_ca.png

[weldbead]

so the plug is silversoldered in??

[MuRCieLaGo]

so the plug is silversoldered in??

Yes exactly!

[Paul Workman]

Yikes! $600 to fix a vacuum leak!? Maybe I'll come out of retirement!

FWIW, I've repaired a few oil leaks with good ol' JB Weld. Works extremely well for that kind of repair. Just a thought!