dubulup

Not hard to start. Initial puff (oil burn off?), then light white smoke lasts 40 - 60s (not sweet smelling).
No champagne bubbles in filler neck during warm up.
Not bogged the first few minutes of driving.

But, my overflow will not stop pissing coolant out the relief hole in the top.

Just install PFS SMIC, with Aluminum AST...not a nice fit, leaning a little forward...(have pics, can't post). Initial thought, the recovery hose (from AST to OF) too much resistance to flow, so I cut it shorter making it as straight as humanly possible...yesterday again, beeeeeeeeeeeeeeeep! After about 75 miles (topped off) or so.

Next thought (already replaced filler cap), eliminate AST all togerher. Will this be a miracle cure for my pissing FD or am I wasting money that could be put towards my rebuild (every little bit will help out, ). I've read every thread that popped up on the "AST eliminat*" search hoping someone had similar problem with the PFS SMIC...oh, yeah this problem only occured after the install (or is it just coincidence???)

TIA

-Dub

Scrub

iTrader: (25)

Everyone has there own opinion on it. I myself am considering deleting it. For one reason I am running Evans coolant and there is no need for the AST and it's just one more thing to worry about and get in the way.

dubulup

So...about my problem??? And the AST???

I was thinking maybe running EVANS, would resolve the issue, but why waste money with expensive coolant (?stuff?) if it might get pissed out the overflow. Will the non-pressure stuff help, ya think? But if exhaust gases ARE forcing coolant out the overflow...there's nothing to do, am I right?

apneablue

Dub, first off, are you on your stock motor? how many miles?
I am currently driving around with bad seals. The CRC stuff has me going since the beginning of the year. Not saying this is your problem but if you have already replaced the caps, and there are no bubbles in the filterneck...hmmm?...If you were able to drive 75miles before you got the warning light it just leads me to think that if you do have a leak it's an extremely small one...When I was leaking I would drive about 10 miles before I lost coolant out the OF...I was also able to start fine and I do have a puff of smoke for about a minute or less...Before i did the treatment it seemed like the smoke lasted for 5 minutes...I ended up doing the CRC treatment and it's still holding at 12PSI. I ran 14psi a couple times the other day and it still seems to be holding. As for the AST tilting...I don't think this is your problem...My AST is attached to my radiator and is leaning to the front of the car about 15°...It has not affected anything...I belive if it's holding a seal at the neck it can be leaning slightly...Just as long as whatever bubbles can move to the top.

Lots of folks are against the blockweld treatment because the saw some photos of a clogged radiator...To be honest, who gives a crap if it clogs the (stock) radiator. Seems like you can pick up a stock rad for $50 used...So you have to weigh the options...4-5k for a rebuild now or ($50 for a rad that could last you for a long time while you stash away cash for a ported rebuild).

Again, not saying you seals are borken but if it does come down to that, I totally recommend the blcokweld treatment.

Just my 2¢

jeff48

My FD is fitted with my old FC filler neck and therefore I have bypassed the need for an AST. AST problem solved.

Now on to you.

Just how full do you keep the overflow bottle? Too much and you will be in a pissing contest all the time.


If exhaust gases are really what is forcing coolant out the overflow but no constant white sweet smoke is evident, then something is really screwed up somewhere.

You said there are no bubbles visable in the system...no bubbles equals no exhaust gases in the coolant. Where do you propose the exhaust gases are entering the picture if not through the water jacket. If through he jacket then you should see bubbles. You say there are no champagne bubbles through warm-up, what about after it is operational temp. What temps are you seeing. If you don't have an aftermarket gauge or a power FC/w commander either get a gauge or borrow one or have a radiator shop test the temps.

What pressure cap are you using? You should have a .9 bar cap, if not, get one.


Too many variables to give you an instant diagnosis or Rx.

SPOautos

after your drained your coolant refilled it did you "burp" the system? Thats the entire point of the ast, it traps air that you release by using the vent cap. That traped air will cause you to over heat if you dont vent it.

Could this be your problem?

STEPHEN

paw140

A few other things come to mind. I would completely replace the hose that goes from the AST to the overflow bottle. If that has any kind of leak, the engine will push coolant into the bottle, but will draw air back in when the engine cools. Also check to make sure your overflow bottle isn't cracked (I've seen some people report that problem on this forum).

Actually, if there are any air leaks in any of the coolant hoses, this could cause the engine to suck in air, and eventually overflow your bottle.

Since you don't have any champagne bubbles, I would tend to think your o-rings are ok.

If none of the other checks fix it, try using some sort of leak sealing stuff. I would recommend against eliminating the AST, especially since you already have it installed. That would not cause your problem, unless the cap is leaking or something. On that note, is there a good seal between the bottle and the pressure cap? I know my Pettit AST is pretty beat up in that location, although it still seals ok.

Good luck.

dubulup

Thanks for all the responses team (long lunch break ),

apneablue - Don't think it's a leak. When I went full NS I replaced all water hoses and they seem to be sealed fine...no puddles anywhere, except unter the OF.

jeff48 - If I eliminate, the FC filler neck is the way I'm going, thanks. As far as seeing champagne bubbles at operating temp, how do I do that without burning my eye *****? This is what I did, cut the end off a Sprite (remix, yuck) bottle and stuck it in the filler neck and started the car and let it warm up. Once warm gave it a few revs and waited for the coolant to come back to where I could see it and looked for bubbles -Thanks Spurvo. I'd like to hear other ideas for doing this if this was not a good way to tell...however it led Spurvo to get a rebuild once he saw the bubbles. When should I see the bubbles? Upon start up I'd assume (yeah, I'm probably an ***), since it seems coolant would drip thru bad seals when cold? I picked up a stock cap at a local dealership - would think they carry the correct one by now but who knows, I had to point to the computer screen as to which part I needed for my "RX-7"

SPOautos - why is it you have no gf? and what's that red X for in your sig. (also any website I can see your car? If my seals are bad I'LL be in Birmingham in the future) When I filled the sys. I pulled the TB hose and filled and burbed...this has been a problem for awhile now, been racking my brain and reading about other FD problems trying to solve...Now I'm voicing the problem in public, since you guys know how I feel...

apneablue

You should see the bubbles on startup (cold start)...

Paw140...If there are leaks in that hose from the AST to the OF It should not be allowing air into the cooling ystem...If my memory serves correctly that hose is after where the AST neck seals...So when the seal on the AST pushes open, that's when that hose from the AST to the OF see any action....right?

P.S. I will say a prayer for you that it isn't your seals cuz it truly sux always getting out of the car looking to see if your car is taking a ****.

dubulup

apneablue - Stock motor; 55k, The CRC fix will take some thinking if I go that route.

paw140 - "A few other things come to mind. I would completely replace the hose that goes from the AST to the overflow bottle. "

That sounds like something I need to do...any idea on that part number? That hose is kind-of strectched to get behind my heat shield, my I rubbed a slight hole in it or something. There is two hoses with a valve between them, right?

Pretty sure the OF doesn't have a hole in it.

dubulup

Good info, thanks.

When exactly does the seal on the AST open? When the system is hot/expanded and the pressure pushes it open, right? Then the coolant will go to the OF, and it gets back into the sys. thru the recovery hose that is from the middle of the AST to the filler, correct? That's where I thought my problem was...then I shortened that hose (to get the bends out) and the same thing is still happening?!?!?!?

I need to learn more about the operation of the cooling sys...

I siphened coolant out of the OF to get the level below F, but then it filled back up and pissed out the top.

apneablue

From what I understand is that the coolant will expand when it gets hot / normal operating temp....If it does then the expansion opens the AST spring seal and the coolant travels down "that" line and into the overflow. I have read that the system will actually suck coolant back into the system from the overflow...I don't understand how that happens.

Ok, I just tried to draw the cooling sys but it didn't work out....

dubulup

I don't see how that happens either, but it has to happen.

It has to get from the OF to the AST to get back to the filler neck. Maybe...naw, I'm not even going to try.

Nice Drawing btw (I saw it before you edited it out, and I got the punchline ).


We need Spurvo to chime in...

93BlackFD

not the map sensor?

dubulup

WHY DIDNT I THINK OF THAT???

I must be the dumbest mothafawker around...

please enlighten me if I am?

apneablue

Why not the map sensor? It seems everyone blames everything on the map sensor...

Problem: My car is pulling to the left
Solution: Check the map sensor!

Problem: I hear a grinding noise in the tranny
Solution: Check the map sensor!

Problem: I hear a clunking in the rear wheel well
Solution: Check the map sensor!


So there you go!

Problem: My Car is pissing Coolant
Solution: Check the map sensor!!

Problem Solved

dubulup

Since the notion was seconded...I'll go check that right away!

paw140

My understanding of the cooling system: there is a hose that goes from the filler neck of the AST to the OF bottle. When the coolant gets hot and expands, it pushes past the spring-loaded seal on the pressure cap and exits into the overflow bottle. When you shut the engine off and the coolant cools down, it contracts. This creates a vacuum in the system, and coolant is drawn back into the system through the very same hose that it exited from. (The path for that hose connects to the bottom of the OF tank, so it can draw in coolant). If there is a leak in that hose, or any hose for that matter, it can suck in air instead of coolant.

paw140

And yes, make sure to check for the champagne bubbles when the engine is cold. To me, it doesn't sound like coolant seals. If it is, it's in its early stages and can probably be taken care of with some block seal.

dubulup

Thanks Paw, I just have a hard time understanding how pressure pushes the cap open (when hot) then when cold, a vacuum is created to suck coolant passed the seal??? Or is the seal still open when it's cooling and the vacuum sucks coolant in, then shuts it after a given temp/pressure? Maybe I have a problem with cooling too fast and not enough coolant comes back...in an FD? Yeah that must be the case!

I'll check that hose...At the rate I'm losing water/coolant, it seems that none or very little coolant gets back to the system...another finger pointing away from o-ring failure...I would definitely smell that kind of burning (I think anyway)

spurvo

Yeah, MAP sensor.

Or turn signal fluid.

Damn, Dubs, not you too!!?? OK, first, let me say I'm not all expert-ish about the cooling system, so I'm not being all preachy. That disclaimer out of the way...

Coolant, like any material (gas, liquid, or solid) will expand as it gets warmer. Literally, the molecules begin to wiggle, and therefore take up more physical space per given number of molecules. So your coolant expands as it gets hotter, even at "low" temperatures, like 156F or 180F. As the coolant expands, it creates pressure in the closed system that it sits in. If we were to simply keep the system closed, it would eventually explode somewhere, so the system is designed to allow a pressure releif, namely the pressure cap that is on top of the AST, or filler neck if you've eliminated the AST. Originally, the pressure cap for the FD opened at 16 psi, but Mazda quickly realized this was too high, and they brought it down to 13 psi, or 0.9 bar for you metric folk. So this means that as the coolant gets hotter, the pressure eventually reaches 13 psi in the coolant system as a whoile, and coolant starts to flow out the pressure cap. In our case, the coolant goes into the overflow tank.

But wait there's more. When you shut off the car, typically the exhaust is sitting at a pretty high temp (I've measured 400C!) and this heat has to go somewhere. The heat (literally wiggling iron and aluminum molecules) flows into the rest of the engine and therefore the cooling system as well (known as heat soak). This heats the coolant even higher, increasing the pressure, and making more coolant flow out into the overflow. This is further exacerbated by the lack of water pump flowing coolant through the system, especially the radiator, so the coolant just sits and gets hot. More overflow. It should be noted that this is often the time that coolant overflows the overflow tank and pees on the ground... AFTER shutoff. Read on..

Now, once the car starts to cool off, typically 30 to 45 minutes after shutoff, the coolant begins to physically contract. The molecules wiggle less, and take up less space. As this occurs, the shrinking volume of coolant in the engine creates a vacuum in the coolant system. This vacuum literally sucks coolant back into the engine from.. you guessed it... the overflow. In fact, the amount that expanded into the tank is the amount that goes back in, if all is working well.

So what can go wrong? ANY leak in the system. Remember that things expand as they heat up. You can have a small hole in a hose right at the hose clamp that doesn't leak coolant during running conditions because of the swollen rubber and hose mount, but when things cool off, the hole allows air to enter the cooling system instead of coolant being drawn from the overflow. So the coolant level goes down, and the overflow level stays high. You go out and fill the coolant that was lost, and the cycle repeats itself. Eventually, the coolant overflow tank gets full, and you pee. Very often, this condition presents as peeing after shutoff only, not while driving. The coolant suystem does not reach 13 psi until roughly 220F, so normal driving where the temp is around 180F (thermostatic control), you don't get overflow. You get it instead during heat soak when the temp rises high enough. Again, this is due to the ratcheting of coolant level in the overflow due to constant refilling and then loss due to vacuum leak in the system, either from pinhole leak int he hose, bad cap or cap/land interface, failing water pump seal (coolant out the weep hole), hole in the radiator, or a leak in the overflow line. And, yes, failing O-rings.

But there's more. I think I've exceeded max post length, so I'll make another reply to finsh the story.

rynberg

Check the hose and replace the AST cap.

paw140

Here you go:
http://auto.howstuffworks.com/cooling-system7.htm

Pretty nice writeup. I really love that site!

dubulup

Less than 5k mi on the AST cap.


And Spurvo, you da man!!! I always love reading your posts! Even the first one when I really thought you had screws up in your head loose.

Can't wait for part II...

spurvo

And to continue...

Another failure is the dreaded O-ring problem. As 'yall know, the intermediate plates and rotor housings are sandwiched together, and coolant runs though the whole mess, just under the surface of the engine. The O-rings, which are really pretty oval in shape, atempt to seal the inside of the rotor area (combustion chamber) from the coolant system, and then another set of O-rings seals the coolant jacket from the outside of the engine. It is the combustion chamber to coolant jacket interface that typically fails. This can occur if you overheat the engine, as this can cause warpage of the various plates, exposing the O-rings (which, stock, are just rubber with a teflon outer coating) to exhaust temps, and it quickly burns a hole in the O-ring. I'm beginning to suspect that early FD's had a different O-ring material altogether, and that they may fail no matter WHAT you do, but that may just be ignorance on my part. Or wishful thinking.

At any rate, O-ring failure has some fun characteristics. First, and perhaps most important, it allows exhaust gas pressure into the cooling system during engine operation. This forces coolant out of the system as it exceeds 13 psi WAY before normal. My failing O-rings would allow coolant to flow out at 125 F or so (I measured the T-stat housing temp with a thermocouple with a hose connected directly to the AST output nipple and running into a bottle half filled with coolant.). The coolant expanded almost immediately due to the increased pressure in the system. Other symptoms of O-ring failure include hard starting, wet spark plugs, and THICK white smoke on startup. All these are due to coolant leaking into the combustion chamber after shutoff. Note that my car started like a champ EVERY time, the plugs I pulled out during the repop were dry as a bone (though black with soot. I don't rev high enough often enough!), and the white smoke, while thick, smelled like typical exhaust. So not all these sysmptoms will present. Other sysmptoms include an inability for the system to retain pressure using a system pressure tester. I put 20 psi on the system (blocked the overflow line) both warm and cold, and it would leak down slowly (down to 15 psi in 20 minutes) with no outside leaks. You can also experience coolant overflowing while the engine is running. This typically presents as wetness under the overflow without an actual puddle AND/OR the add coolant light coming on while driving fair distances after filling the coolant system prior to driving. I would typically lose 200 ml of coolant on a 45 mile round trip. I would have to add coolant EVERY time before I started the car. I would lose less coolant during shorter drives, more on longer drives. Since everything else was running ok, I just made sure I topped it off every time, didn't drive far, allowed lots of cooloff time to allow refill, and generally just got the new engine dealt with as quickly as possible. I agree I could have run the CRC block weld, but I have a brand new Fluidyne in there, and if it clogs radiators, it clogs heater cores too, and THAT requires pulling the entire dashbord to fix. Uh uh. Another tell tale is bubbles in the cooant filler neck while the engine is running. From what I've read, bubbles will present on cold startup almost all the time, even in a healthy engine, as not all the surfaces are perfectly mated until warm, but this may be wrong. The test I ran was to use the Sprite bottle like Dub said above. I cut the body off halfway down the bottle, stuck the opening of the bottle into the filler neck to make a nicely sealing funnel, had the g/f start the car, and revved it to ~2000 rpm. I did this with the coolant level a couple inches below the filler neck at startup. The coolant expanded immediately to fill 1/4 the way up the bottle, and a froth developed in the coolant surface that looked EXACTLY like champaign bubbles.

Thats all I know. the Pineapple rebuilt reman is in, it runs, and does not require coolant after 4 running cycles. Expensive fix.

Dubs, I suspect the worst in your case, because you are losing enough coolant to get the low coolant light after 75 miles of driving, having started with a full system. Even air pockets in the system will not boil over so bad as to lose that much coolant, and air pocket will go away if the system is working properly (no leaks, and you've replaced the hoses). Try the sprite bottle thing again, both cold start up and warm (mine bubbled under both conditions), and you can also try running tubing into a bottle half filled with coolant from the AST nipple. If the coolant expands into the bottle while the temp is still below roughly 220 (if you only have the stock temp gauge unlinearized (I can't recall if you did this!) you can turn on your lights and the fans will go on at 210 F as a rough measure of temp) then you should suspect the worst.

That's what I know. Also try putting a pressure tester on the system. It should hold 20 psi all night long with the overflow tube blocked (I folded the hose and placed a vise grip loosely 1/4 inch below the fold to shut off this escape path for coolant).