1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

At wits end finding an elusive vacuum leak

Old 06-14-19, 12:37 AM
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At wits end finding an elusive vacuum leak

Spent a whole 10 hours today replacing the upper and lower intake gaskets on my GSL-SE - what a PAIN. The old ones were junk and pretty much bonded to the irons and manifolds - someone siliconed the old upper gasket as well (didn't even replace it by the looks of things). I replaced them as spraying carb cleaner around the injectors and lower manifold gasket the motor smoothed out and idled well. After replacing them, I'm back to square one. Same spot, still leaking.

I'm wondering if the injector grommets may be the cause, as well as some parts for them. They were pretty malleable and not rock hard, seems like they seated ok. Unsure if the "pintle" piece was on there as well as the screen, there is a piece in the irons that has 4 small holes. Replaced the oil injection vacuum lines too as they were rock hard and broken (also broke the plastic vacuum spider piece and joined a few T's together to macgyverr it).

Pretty much lost at this point on what may be the cause in that vicinity. Don't have a smoke machine either, but my work may be able to smoke it.
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Old 06-14-19, 05:31 AM
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Replacing the lower intake gasket is a chore as the gasket is ALWAYS stuck to the manifold and to the engine and is terrible to get off. I have never had to replace one on an SE and would never unless I were certain the gasket had failed. Also, ensure that you do not remove the dynamic chamber from the runner set as that gasket is no longer available. Also another gasket that I've never seen go bad in 20 years of RX-7 ownership.

Replacing the seal kit on each injector is a must if you removed the injectors. At this point in the car's life, I would replace the seals just as preventative maintenance. I would also take the time to replace every vacuum line on the engine and to the two solenoids that are bolted to the right side of the firewall.

Have you looked into leaking throttle shaft bushings on the throttle body? The bushings can wear, causing a vacuum leak that can be frustrating to find. I would go through and inspect each rubber hose on the engine for any cracking or loose fitting. Spray the throttle body and see if the idle smooths out.
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Old 06-14-19, 08:06 AM
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On replacing a failed 13B engine under warranty-or afterwards,the worst,tedious part of the job was cleaning up gaskets. LIM in particular,in the past I have joked you could drive an SE with all LIM hardware loose/missing and it would run fine due to the heat cycled Bakelite like gasket with its death grip on components on either side

I canít seem to find the thread,real sure recently responding to a very similar thread about this topic and thread starter posting finding a vacuum leaks in area of LIM and intending to replace that gasket.
I recall instructing op to revisit leak testing to try to pinpoint source of leak just as 1st responder to this thread has. Also recall saying failures of this gasket near nonexistent- except after gasket/engine replacement where hardware left loose or not tightened properly.
Think I recommended to op to renew all vac hose on engine as they can have cracks and spits particularly on their undersides that arenít seen and sometimes donít react to leak testing.
Anytime you have the manifolds off these engines after all the years on them the vacuum lines should be inspected closely. Having to go back and find a vacuum leak on a poor idling engine after having it apart for other repairs,requiring disassembling what just put together will sour your day
Like above,I include injector o ring replacement while in the neighborhood.
Op good luck in search and post back findings to benefit future readers of this thread.
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Old 06-14-19, 06:41 PM
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Originally Posted by mazdaverx713b View Post
Replacing the lower intake gasket is a chore as the gasket is ALWAYS stuck to the manifold and to the engine and is terrible to get off. I have never had to replace one on an SE and would never unless I were certain the gasket had failed. Also, ensure that you do not remove the dynamic chamber from the runner set as that gasket is no longer available. Also another gasket that I've never seen go bad in 20 years of RX-7 ownership.

Replacing the seal kit on each injector is a must if you removed the injectors. At this point in the car's life, I would replace the seals just as preventative maintenance. I would also take the time to replace every vacuum line on the engine and to the two solenoids that are bolted to the right side of the firewall.

Have you looked into leaking throttle shaft bushings on the throttle body? The bushings can wear, causing a vacuum leak that can be frustrating to find. I would go through and inspect each rubber hose on the engine for any cracking or loose fitting. Spray the throttle body and see if the idle smooths out.
Looks like I'll be pulling the upper off and replacing those seals then. I think I recall someone else having a similar issue and found out it was those o-ring gaskets. As far as the throttle body goes, the shaft has little to no play in it. Recently took it off, cleaned it, and lubed it. If that doesn't do it, I'll see if someone could sneak my car in for a quick smoke down.

Originally Posted by GSLSEforme View Post
On replacing a failed 13B engine under warranty-or afterwards,the worst,tedious part of the job was cleaning up gaskets. LIM in particular,in the past I have joked you could drive an SE with all LIM hardware loose/missing and it would run fine due to the heat cycled Bakelite like gasket with its death grip on components on either side

I canít seem to find the thread,real sure recently responding to a very similar thread about this topic and thread starter posting finding a vacuum leaks in area of LIM and intending to replace that gasket.
I recall instructing op to revisit leak testing to try to pinpoint source of leak just as 1st responder to this thread has. Also recall saying failures of this gasket near nonexistent- except after gasket/engine replacement where hardware left loose or not tightened properly.
Think I recommended to op to renew all vac hose on engine as they can have cracks and spits particularly on their undersides that arenít seen and sometimes donít react to leak testing.
Anytime you have the manifolds off these engines after all the years on them the vacuum lines should be inspected closely. Having to go back and find a vacuum leak on a poor idling engine after having it apart for other repairs,requiring disassembling what just put together will sour your day
Like above,I include injector o ring replacement while in the neighborhood.
Op good luck in search and post back findings to benefit future readers of this thread.
Yeah, that was me lol. Hind sight is 20/20 and kinda regret it, but at least I've seen the magic behind the 6 port system and a possible freeze plug that is seeping some.
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Old 06-15-19, 01:24 PM
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Once its running, spray the throttle body near the throttle shafts with brake clean to see if there's a change in idle. Worn throttle shaft bushings don't necessarily cause the throttle shafts to have noticeable play.
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Old 06-27-19, 08:25 PM
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Alright. Changed out those injector seals and it helped it some, but still has some sort of vacuum leak in that are. Couldn't get the top seal pushed up into the rail, not sure if that matters or not? I did notice there is a black canister near the rats nest that I wonder if the line to it may be brittle (didn't have enough hose on hand to replace it). Don't know what else it could be at this point besides maybe the oil injectors (already replaced the vacuum lines to them)? It's only in that specific area where the injectors are at that if you douse in carb cleaner it really smooths out and idles well.

Originally Posted by mazdaverx713b View Post
Once its running, spray the throttle body near the throttle shafts with brake clean to see if there's a change in idle. Worn throttle shaft bushings don't necessarily cause the throttle shafts to have noticeable play.
Sprayed it down, didn't make a difference unfortunately.
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Old 06-27-19, 08:41 PM
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Check the o-rings on the injector diffusers. I went crazy chasing a vacuum leak and it turned out those seals dried out and cracked. The diffusers are plastic and mine completely broke when removing them, so you might just be better off ordering complete replacements.
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Old 06-28-19, 07:39 PM
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Originally Posted by klptk View Post
Check the o-rings on the injector diffusers. I went crazy chasing a vacuum leak and it turned out those seals dried out and cracked. The diffusers are plastic and mine completely broke when removing them, so you might just be better off ordering complete replacements.
Diffusers? I know there's a plastic piece in the injector hole that I assume atomizes the fuel (a few small holes in the tip), otherwise haven't heard that term before. I did replace the lower o-ring seals on the injectors if that's what you're referencing.
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Old 06-28-19, 11:01 PM
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Yep,the plastic piece! It has its own seals. Those went bad and were giving me a leak around the lower injector seal.
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Old 06-29-19, 06:51 PM
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Originally Posted by klptk View Post
Yep,the plastic piece! It has its own seals. Those went bad and were giving me a leak around the lower injector seal.
Oh lovely...

I'm sure Mazdatrix loves my business lol. I'll give that a shot as well as replace all the vacuum lines and see if that'll help it.
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