Frogman

So my smokey tail pipe has led me to conclude AFT is getting sucked into the engine at about 1 quart per 100 miles. I have checked the bottom of my car on a lift today when fixing my muffler today ( didnt solve any smoke issues) and we found ZERO leaks . The oil level is identical and so is my coolant , marked it with a marker and everything.
The car smokes when in stopped but stops smoking after any movement . Is there any vac valve that connects the trans to the carb ? **** the smoke even smells like burnt atf .

mazdaverx713b

iTrader: (91)

There's no way for the transmission fluid to be able to get into the engine on its own. The coolant, yes. And if the engine is consuming coolant which is contaminated with the trans fluid due to a bad trans cooler in the radiator, then that can happen. You would likely see coolant loss at that point and potential overheating.

If it smokes when stopped, do think think that you have an oil leak onto the exhaust manifold and when you get going you no longer see the smoke due to airflow? That sounds more logical to me. I would start by inspecting for a front cover leak or omp leak.

If you suspect the smell is burnt trans fluid, then perhaps the trans cooler lines, the trans pan, tailshaft seal or pump seal are leaking trans fluid and its getting onto the exhaust and burning. Time to get the car in the air and inspect it for leaks.

j9fd3s

iTrader: (3)

the vacuum modulator is connected to the engine, and when it goes bad will let ATF in

KansasCityREPU

iTrader: (9)

I wonder if a PCV valve in the trans to carb line would help?

t_g_farrell

iTrader: (1)

If this is an automatic, then what j9 says is the cause. When the modulator on autos go bad they leak and the vacuum on them pulls fluid into the engine. If its manual, I have to wonder where any ATF would come from at all.

Frogman

I sure hope it's an auto.. LMAO.
Yes, it's an auto. and no I don't have any oil leaks, the oil level has remained stable for 700 miles. Plus the engine has 4000 miles on it since it was rebuilt. I'm sure any incorrect gasket placements or errors would have reared their head in long ago. My cooling is actually quite great. The car never goes beyond the 1/4th mark unless ist 100 deg outside and then it goes up between 1/4th and half, the reserve tank has been marked where the low normal is and where the high normally is and I check it every day. The only fluid being lost is ATF, and my ONLY ATF leak was at my speedo gear, I fixed that and the smoking commenced about a week after, and then the ATF marled L . Also there is not a way for ATF to seep into the engine via gasket failure , but I do know the carb and or engine regulate the pressure valves, so I assume one of those valves is sucking **** in. If it's my intake leaking..

I have emissions stripped vehicle so leaks are incredibly easy to spot.
and I made this issue worse by adjusting the carb ( i made it consume more of what was burning) the carb would never cause it to suck more oil .

peejay

I bet if you pulled the hose off of the vacuum modulator with the engine running, ATF would drool out.
Not sure where it is on the 3N71, but I sure replaced a lot of them on Ford C6s.

Frogman

There is no physical valve running from the trans to the engine or carb that I can see, The vac diaphragm is just a little nub that you can unscrew . If you have any hunch please do tell me, I can check that super easily. I can take pics of my carb if you want as well !

Frogman

After a lengthy look at the parts diagram,I found that there is indeed a line from the trans to the engine Look at part 19910 .
https://partsouq.com/en/catalog/genu...=&uid=26431&q=

This part connects somewhere . and I suspect this is my headache. And I will fix two birds with one stone. I suspect this part has been damaged for a while but the damage was minor and it would only suck up small amounts of fluid, but now it's full-blown damaged and sucks fluid big time, ironically the part still does its job since it still creates vaccume, I suspect it creates a negative vac ( towards the engine) when the car is stopped /decelerating. and a positive vac ( towards the trans) when I accelerate. On the way home today, I got zero smoke from keeping the car above 2k revs at the stoplight by popping it into neutral. When I stopped to get gas *( my old gas was seafoam + Lucas, this concoction fixed my truck fouled fuel system in 15 mins haha) , the car didn't smoke on startup when I turned it on and didn't smoke for the entire low rpm drive home until I got home and waited 5 mins, and sure enough, here comes the smoke, and cleared out after another min of accelerating after 1k. If it was a blown oil ring or even a leaking exhaust, the smoke would keep coming out. I seriously doubt 500 revs would clean burn an oil leak.. **** a blown oil control ring would get worse under load unless it is that cool failure that only smokes out under a low gear deceleration .. LOL .

Frogman

I found the tube that connects to the base of the carb this morning and pulled it, the car idles roughly without it, but the idle was fixed by plugging it . The pipe had a bit of atf in it , when I mean a bit, I mean just residue , but wet none the less. THIS part should be BONE dry.
Once plugged, I let the car idle for 10 mins and i got zero smoke, even after reving it and waiting another 5 min's . I had my mom keep an eye on the tail pipe during revs to make sure no smoke was generated, she confirmed there was no smoke. I popped the tube back in and sure enough, within 60 seconds the smoke returned . My theory is the car sucks the fluid when I drive and during idle it burns it less efficiently and causes the smoke.
I will replace the bit this weekend and hopefully the issue will be resolved . Fun fact, when I plugged the hole the idle was as perfect as I have ever seen a rotary engine run, no vibrations, a constant smooth drone. Thank you to the german guy on here for helping me tune the carb a few days ago, he really hellped me get the carb mint! .

t_g_farrell

iTrader: (1)

Sound like you have it sorted.

Frogman

Hopefully this is the issue. Looks like I do though .
I will report back once i change teh part. I have been told by a few dozen folks there is no way the engine can suck ATF fluid in ..

peejay

Probably people who aren't old enough to have ever worked extensively on non-electronic automatics. Vacuum modulator to control shift feel and, to a degree, the shift points, and a separate kickdown linkage or switch. The main shift point control is the governor, which is essentially just like the mechanical advance in the distributor, uses weights and springs to move a spool valve in and out depending on output shaft speed. The two balanced off of each other to control the transmission.

SOME automatics just used a "TV" cable in addition to the governor. Throttle Valve. Took the place of the vacuum modulator and the kickdown linkage all in one. IIRC all overdrive automatics used a TV cable no matter which (Big 3) manufacturer it was, so going back to vacuum modulators means early 80s at the latest.

Frogman

Jerry rigged this filter in the vac line ..

Look ATF !

t_g_farrell

iTrader: (1)

The good news is you don't have to premix!

peejay

That air filter housing makes me smile in all the ways.

Frogman

I got my hands on a new old stock vac modulator from 1978 fpr 32$ off ebay with paperwork and everything, vintage mazda goodies . 20 min job, i spent more time breaking the old crusted out air line than anything else , ATF poured out! . Flushed the air line, installed new lines, and modulator and let the car warm up.. no more smoke period, the exhaust is crystal clear. Im going to go back to 1 ounce per gallon of premix but im sure its fixed, before after 5 mins i got constant smoke that cleared up but then got worse if i drove then stopped .
For future reference, to all who own autos, if your smoke is white and coolant seems level, check the modulator by using that trick i did . Buy a generic oil filter and splice it into the air line , if an fluid pools in there your modulator is bad, be sure to drive it around for about 15 mins, my issue only manifested when driving until the modulator fully broke, that means i had no smoke except on start up and my atf was slowlly getting drained . They sell them ( miata spec , but they fit) at atkins . Honestly the only change i noticed in shifting is it shifts earlier when i floor it and won't rev hand when taking hadr turns any more . Hard turns would spaz the tranny out before.