coolant problem (over flow tank)
 

i have been searching for weeks about this cooling problem i am having. replaced AST cap, the filler cap looks great but will soon replace that also. i loose coolant every now and than. my buzzer will go off and the temp will rise, it seems that my coolant was not returning into the system..i thought it was a air leak somewhere.. turns out the main tube going from the over flow tank back to the engine is has came off or devolvped a hole/leak.. i pur water into the over flow tank and it just goes to the floor just as fast... so questions? how do you get to the tank? behind the passenger front side wheel well? any write ups or links would be awesome as i have been searching forever and since iam on 56k =( i cannot d/l the FSM

To get to the overflow tank, you have to go through the wheel well.

How far does the coolant temp. needle go up? Is all your cooling system working properly?

Two possibilities here.

First off, check the level in the overflow tank. You check it like an oil dipstick. If it's where it should be (between empty and full) and not leaking, it's fine. If you overfill it, it will leak out.

If the hose between the overflow tank and the AST is popped off, hole in it, whatever, that's bad. Fix it.

As coolant expands with heat, you have to have somewhere for the expanding coolant to go - the overflow tank. When the car cools off, it should suck it back in from the overflow tank so you always have a full cooling system. If that line is bad or popped off, coolant will push out, not be sucked back in, you have air in the system and overheating problems.

Now, if all that system works well but it still is constantly pushing into the overflow tank and not recovering, you may have a bad coolant seal in the motor. If so, you can use the block weld fix to buy you quite a bit of time. It's time consuming to do it RIGHT, but it does work.

If your overflow tank is truly broken and leaking, fix it NOW. A good used one should be reasonably priced. And, yes, you do pull the passenger wheel off and the wheel well liner off to get to the tank.

Dale

coolant system has been replaced 40-70k ago with new engine.. the temp gauge stays almost half way all the time... than the car will spit the coolant into the over flow...leak out and not come back in...mostly...when cooling down from driving i.e idling than the temp gauge will rise and buzzer will sound by the time the hood is open and engine is soon shut off... the temp gauge doesnt go past 75% at anytime if that i know i shouldnt trust the stock gauge do i have to remove the wheel to get to the over flow tank or can i just turn it?

i just checked the over flow thank.. and it is full and so is the AST but the filler neck is not.. the car idles fine no smoke on start up and has no problem's on cold starts even in the winter..can it have a bad or worn seal and still act this way?? so now i need to check for all air leaks? i need to go replace the AST cap for the hell of it.. could the over flow tank have a hole in it somewhere to the engine where it would stay full but leak out when returning to the engine?

btw i already replaced the AST cap i meant to say i need to replace the filler neck cap for the hell of it ;]

<img src="www.http://i38.photobucket.com/albums/e149/cbm7/e8cbcf75.jpg.com" alt="93 r-1" height="250" width="250"></img>

<img src="www.http://i38.photobucket.com/albums/e149/cbm7/e8cbcf75.jpg" alt="93 r-1" height="250" width="250"></img>damn typo

Your coolant overflow problem may be a tell-tale sign of a bad coolant seal. Do you have any white sweet smelling smoke at start-up?

Do a search for the "Champagne Bubble Test" and do it. That will tell you if you are getting exhaust gasses into to your cooling system. These exhaust gasses will displace your coolant in your system and cause it end up in your overflow bottle and not in the engine.

Bad coolant seals = the need for a rebuilt motor. You can't fix or replace the coolant seals w/o removing and opening up the motor. $5000. Give or take some $$$

Look up "block weld", many people on the forum have done this to "fix" a leakiy O-ring. Many say its only a band aid and doesn't really worko and some guys have had great luck with it. Where the "fix" worked for 1-2 years. It's definitly worth a try.

Good luck.

car idles fine great cold start ups no smoke.. oil looks clean ( clean as any rotary could ) boost great hot starts fine..could there be bad seals or worn seals enough to leak but still act normal? passed smog test CA smog test i might add... months ago

btw engine codes reading. = ait temp sensor and egr vavle

If you are getting the air temp sensor code, that's not a good thing but it won't cause this problem.

Have you checked your thermostat yet?

Fix the air temp sensor problem (bad sensor, disconnected plug, or wiring problem) and then check your thermostat to make sure it's working properly.

i havent checked my thermostat..- could it be the item behind my coolant problem? i would not think so.. and when the ecu gets the error from the air intake sensor.. it just goes to a defult setting ( i.e runs richer ) thinks the air is always at ( )º ??

ok so today i went to work on the car removed intake box.. removed intercooler and other parts.. removed pass. side wheel well cover to expose the over fill tank.. everything looked good.. i than started the engine let it run and build pressure topped off filler neck before i started it.. same with over fill tank watched filler neck when started.. capped it.. built pressure i could see no leaks i ran it for 20 mins temps were fine shut her off for good and let her cool down.. opened filler neck and it was an inch from the top 1/2 an inch to an inch... where did the coolant go? i than topped her off...(filler neck) waited 10 mins and it was down 1 inch again... topped her off ( now it looks fine ) iall check in the morning... now could the system build pressure and still have an air leak with no coolant leaks?? i replaced my AST cap next will be the filler neck cap.. if i replace the filler neck cap AST cap and still have problems with the coolant returning from the over fill tank to the engine what would it be??
i checked all lines going to and coming from AST checked all RAD hoses looked by the turbo coolant lines and so fourth..iam really stuck here summer is coming and my third gen needs the love!!( so do i...)
could a coolant hose somewhere in the engine have a small air leak? to cause this and how would one find such a thing? btw my car does not smoke on start ups.. pass's smog CA smog, runs great all the time everytime besides this coolant thing =/ i will replace the filler cap tomorrow..put everything back together take for a run and hope for the best! please help anything would be great thank you

What type of cap do you have on the AST? If it's the "safety" type with the red pressure release lever, I just had to replace one of those and it was new. I guess those are prone to leak. It was not sucking the coolant from overflow tank back into engine.

a have the one with the safty lever (red) 16 lbs cap on the AST
one the filler neck is just a normal cap no spring

any advice if i replace both caps and still no coolant going back to engine from over fill tank?

I had that issue not too long ago, I replaced the AST cap and problem went away. I think the no pressure cap on the filler neck should be ok. Sometimes the AST neck is warped and won't get good seal on pressure cap. It kept filling the overflow tank, not sucking any back. Pretty soon it started do flow out of the over flow tank.

that is my exact problem! after awhile it will flow out of the over fill tank... wont suck any back in so iall replace the AST cap again for shits and giggles and than replace the filler neck cap iall check the AST neck for warpage thanks for the info..

Good luck! And don't get the cap with the saftey lever!

question? is there a cap on the RAD on the third gen? or just on the AST and filler neck.. if there is one on the RAD.. i couldnt see it btw i have stock RAD so is there three or two CAPS for the third gen

Only 2.

There are only 2 caps on the stock system - a pressure relief cap on the AST and a simple sealing cap on the filler neck.

Before you do anything drastic like block weld, make sure that the AST cap is good and that the hose running from the AST to the reservoir tank is air tight. It is not a pressurized hose, so it is possible for it to not leak coolant but still have a small air leak that defeats the vacuum needed to draw coolant back into the AST from the res tank as the system cools. (On the factory AST, no clamp was used on this line -- it was just a wedge fit that works loose with time.) Sometimes all you need to do is install a hose clamp on this line at the AST nipple.

Also make sure that the line's couplers are sealed and that the line is connected properly to the pickup inside the res tank.

what color is your coolant...green i would assume or i feel u would have changed it already. umm...i did actually have same kinda problem and mine ended up being the thermostat...still looking for the AIR INTAKE THERMOSENSOR tho....lol. good luck.

Are you trying to find where it is, or are you looking for the part? It's located right under the UIM it is blue and sits vertically. If you're looking for part, the used for sale section or call Ray at Malloy mazda.

Have you checked to see if you have a leak in your O-rings yet? Check to see if you are getting exhaust gasses in you cooling system. Do the Bubble test. At lkeat you can eliminate that as a cause for air getting to your system.

Can you smell coolant from the engine bay? I had a the water pump housing leak where it meets the engine block. It was a bitch to find.

if one (me) took the tube from the AST leading to the over flow tank.. created a vacuum (sucked from the hose) and got coolant (taste's so good) would that test ok? if there was an air leak.. i would be sucking in mostly air... with little or no coolant right? i got coolant from the hose no problem..so feed backs on that..

also would/could a T-STAT be causing this problem?

That is something else you should check:

https://www.rx7club.com/showpost.php...7&postcount=14

is the T-STAT in the same (area) as the second gen...
i have not yet to remove it on the third. i just searched all of my fav sites.. and none give write ups on the termostat removal.. would it be the same as "water pump removal" i have my intercooler + intake box + pass side wheel well cover off/out anyone know of a good T-STAT removal + install page? thanks

btw. after wokring on my third gen it make's my second look like a cake walk

If you take the coolant filler neck off, it's right there, not too bad to get to.

1.)well any info on how to do so? 2.)could i do it just as easy with the intercooler + intake box back on?? because i would like to put it back on asap..

http://mahjik.homestead.com/files/FD...iller_neck.jpg

The T-stat housing is circled above. Remove that (the unit, not just the neck) and the T-Stat is right there.

I had the same problem. Replaced the AST and filler neck caps, problem would go away and then come back a few months later.

As of a month ago it started to do it again. I was at my mechanic's getting a PFC installed and tuned. I told him that I was having an overflow issue and he set the fans to come on at 85 deg C (which he does anyway). Without changing the caps the problem disappeared.

As it turns out my coolant was getting a little too hot and thus overflow... I should really look into it (as in why), but at this point no more problems. Before I had to refill my AST every two days, now I haven't done it once since I got the PFC. Since nothing was changed other than at what temp the fans turn on I consider the problem solved.

[QUOTE=RX7 allnight]if one (me) took the tube from the AST leading to the over flow tank.. created a vacuum (sucked from the hose) and got coolant (taste's so good) would that test ok? if there was an air leak.. i would be sucking in mostly air... with little or no coolant right? i got coolant from the hose no problem..so feed backs on that..QUOTE]

You might want to use a MityVac Plus instead of your mouth, but the test would be ok if you do this test once from each end of the hose, with the other end connected or in place as normal. The problem with this hose is usually that it draws air where it slips over the AST nipple on the stock setup. Installing a hose clamp there is the simple fix.

i installed hose clamps along that ast to overfill tank hose and it has since stopped the overfill leaking problem i've had for the past 2 months.

my thermostat was shot..replaced it
checked all coolant lines to/from AST
replaced both caps AST/FILLER
installed hose clamps on AST to/from
now.. with car shut off i cant seem to keep the filler neck topped off..
topped it off started the car let the t-stat open.. capped it went for a drive.. checked filler neck and it was low.. topped it off with engine (off) checked it next day it was a little low.. is there enough air in the system to cause this? slowly leaking out top cause a low coolant level in the filler neck? any info thanks

The system can absorb quite a bit of air unless you're very specific with the filling. When filling, it helps to 'burp' the upper radiator hose right in front of the water pump housing, and to do the fill with the coolant hose disconnected from the throttle body near the firewall.

Or, just run it and top off as the level goes down. It will eventually purge all the air.

Dave

I had the same thing happen to me when I changed my T-stat a few years ago. It took me almost a month to get all of the air out, even though I only drove it about 30 miles that month.:)

so today i went out and did the champange bubble test.
my car was dead cold.. started it with filler cap off. it started to rise with no bubbles for a good long while i give it a bit of throttle maybe 2-3k revs to get up to temps. than all of a sudden ( untill T-stat opened i think ) i saw many fizzy tiny bubbles =/. it was very consistant and didnt stop. it was new years all over again.
is this my O- rings? or could it be a air leak? i have read and heard many things about the block weld method what do you guys think? did i do the test right?

That sounds like you did the test correctly.

I would take it to a shop that can test the coolant for exhaust gases, or to a rotary shop that can confirm the problem. Might as well put an extra $100 into diagnosis before putting 1000s into a rebuild.

That sounds like a pretty hefty coolant seal leak. I would research the block weld idea to see if it will have a chance of working at all in your case. One thing is clear: there is a very specific procedure for the block weld thing, follow it precisely. Half-ass it and you'll have gunk in your cooling system and no improvement in the engine.

Dave

so i got a pressure tester and i tested the system. to my shock i noticed coolant coming from bottom of rad, and near the fire wall i have never seen coolant on the ground. now question is. i did the champange bubble test. could these tiny fizzy bubbles be from air leaks? through out the system? i ran the system to about 20-25 psi

went to my local smog shop and put the sniffer down the filler neck, with the engine at normal op. temps turned the car on and the sniffer dectected nothing! yay.. put a rag around the hole of the filler neck with the nozzle inserted just to make sure and still nothing. so a small air leak could cause this many bubbles with no visual coolant on the ground (leaking) but still be enough of a gap to make the over flow bottle not return the coolant?

??

^

it might be worthwhile to just replace the coolant lines. im having coolant problems myself at the moment :) frustrating isn't it

Sounds just like me.. I know this thread is old but any new news??

what are the proper methods used to refill the 3rd gens cooling system?
my system still boils i dont think i have enough coolant to water ratio. my system holds pressure i used the pressure tester for like 12-18 hrs and it maybe dropped a few hairs maybe 1/8 of a psi i was told to only test it for 10 mins to see if coolant seals were bad but i thought i should just leave it as i heard of other people trying to find leaks does this mean my seals are ok? so why is my system still boiling and overflowing out the overflow? with my system pressurized via pump i have turned the motor over and pulled the plugs and their dry as a bone i removed my ast a bit ago due to it cracking inside maybe some of the pastic is blocking my RAD or anorhter passage? thanks for your help iam going to drian my system and make sure proper coolant/water ratio is used

Boiling out the overflow is a sign of temperature at some point in the cooling system exceeding the boiling point of the coolant. It could also be a sign of trapped air.

Possible causes are:
1) bad AST cap not holding pressure (not likely, you did a pressure test)
2) not enough A-F to raise the boiling point enough to prevent boiling, especially critical with the OE thermoswitch
3) coolant seals allowing exhaust gasses into the coolant, but the seals don't leak coolant into the combustion chambers

Solutions:
o Higher A-F to water ratio (50/50 is normal, up to 70% A-F can be used, but reduces cooling efficiency)
o Higher pressure AST cap (puts more stress on the system)
o Install FC thermoswitch to reduce coolant temperatures
o Hydrocarbon coolant analysis to rule out coolant seal problem
o "burp" the system to remove air pockets - many threads on this

Dave

i did the sniffer test at my local shop and no signs of HC's iam burping the system as we speak. so it is possible to have exhaust gasses pass the seals but when pressure testing not have coolant go the other way. thanks iall post when new results come

so i took my engine out removed everything now iam done with tear down of the block the seals were intact. but didnt look that great.