1986 RX-7 GXL (S4)


Hello. This is my first time posting in this forum. I hope with your help I can solve this issue that's been going on for a while. To start of, as noted from the title there are 2 things to this mayhem. I've been running around in circles searching for answers, buying parts, trying new tricks, and nothing has worked.


First off I'm having a stumbling idle at cold start. It does blow smoke for about 30 seconds to a minute max at start. I never took note or noticed this until about a week or so after getting a down pipe welded on with exhaust tips. (It's basically straight piped to the hks tips) after she warms up the stumbling idle goes away. To describe this type of Idle, when started it revs to about 3.5k then slowly drops down but as it's dropping it moves up 200-500 rpm and continues to do this in a cycle until 1k. It revs at 1k for about 4 minutes then drops to 750 rpm when fully warmed up. Once there it idles smooth with no problems.


Other things to note, I did the exhaust setup because my air pump went out thus was not helping the car warm up properly. That's why I deleted the cats with the down pipe to help flow. I've read some threads on it could be bad injectors I have yet to try this as I don't want to throw money for new ones if they are fine. She does smell like she runs a little rich lots of gassy smell, she also pops just other things to note.


Second thing is my biggest concern and is why I can't drive the car for long periods of time. She's my only car to commute and this is my number one priority to fix. The overflow tank likes to overflow and push coolant slowly out of the reservoir. I have changed the thermostat, replaced the old radiator with a new Duracell one from AutoZone and replaced the filler neck because it broke from to much pressure. I have pressure tested the system more than 20 times and it's passed every time. I have flushed the system twice, the first time with the old radiator (didn't do much) the second time with the new radiator and the lisle funnel (drove very nice for about 20 miles or more than went back to it's bull$$&+) it seems I'm getting pressure somewhere in the system either from air pockets some how or something else entirely. With the new radiator it has a cap unlike my old one so what I did was block off the nozzle to the overflow and I have a new cap coming in for it. Also have a new overflow tank coming in to see if that helps too.


When flushing the system with the funnel I do want to note small bubbles did constantly come through while running the engine and having the heater on full blast, they never go away but I ran all the big bubbles out of the system. My heater does not get hot but I do not have any leaks that I see underneath the car.


Sorry for the long post, I thought I should make this as detailed as possible in hopes someone would read this whole thing and bestow me with some possible answers of light from the Dorito gods. Thank you. Please HELP!

 

You almost certainly have a coolant seal failure.

 

That's what I thought but it doesn't blow smoke constantly, doesn't smell sweet and that it's passed the pressure test so many times.

 

How long does it take to feel pressure on the upper radiator hose from a cold start?

 

U sure have a water seal leak. It is small and is exhaust gas pushing the coolant out in the reservor . A pressure test wont allways pick up a leak like you have it is an exhaust gas leaking in to your water gallery which is much higher pressure than what you test a cooling system at

 

Never checked this, I will today and get back to you on that. I will note it never overheats (does not feel to hot you have to let go) on the top, bottom and TB hose.

 

Going to take your word with a grain of salt. I'm really hoping it's not. We don't have a rotary shop out here in Vegas and I'm really not trying to put the work in on rebuilding a engine. Going to see what the new rad caps and new coolant reservoir do. If it's still acting up my mind is open. (Still feel like it's something small, runs and drives very well besides the overflow issue) thank you for your solid advise.

 

Why replace the coolant overflow tank? it serves no purpose then to holds coolant. If it hols coolant, it's not broke/a cause of the issue Replacing the cap is ok, but is not the cause of this issue.

A rotary can run well with a bad coolant seal.

 

Just trying everything I can from reading threads. People say the overflow nozzle can get clogged and thus not push coolant back into the system. If you have any other ideas please throw them at me.

 

get a tester that checks the coolant for combustion gases.

 

Think about the way the overflow works. When the system gets hot, it can push coolant to the overflow. In your case, exhaust gases or something is pushing coolant to the tank. If coolant can get to the tank, this tell us it can get back to the radiator and isn't clogged.

I had this exact same issue on my 12A. It was so bad that the pressure was sending coolant 10 feet out of the weep hole in the overflow cap. it's a small pin sized hole.

 

Closing this thread up. As much as I didn't want it to be since I've tried everything to pass this objective. It is and for sure is blown seals. To the people who gave advise I really do appreciate it. She'll be up and running hopefully soon. For anyone in Vegas that's needs a shop I highly recommend "Rodmodz" met the owner and is a very nice guy with cooz coze of knowledge from sema builds to owning a 13b sa.