misdbman

I would also first lean to a coolant system leak. As the car gets hot it expells coolant into the overflow tank. If you have a pressure leak somewhere the coolant system will run at a lower pressure and the coolant will boil when the car is turned off. When the system cools off, it is supposed to suck the coolant back into the motor. With a coolant leak this does not happen and you need to constantly refill at the coolant neck. Also, over time this causes the overflow tank to have too much coolant in it, causing more on the ground. The rotary does expell some air into the coolant even with a good motor - that's why Mazda put in the plastic air-separator tank.

If you have a bad seal, the coolant will overflow with the motor running. This happened to my 2G for a couple of years prior to losing the motor.

Just never run the car hot...make sure you keep up with the coolant until you get it fixed.

MILD7

Again, thanks for all the help... I just got back from work and will be heading out to the autoparts store for a pressure tester thingy. One thing I noticed but failed to mention, was that everytime I pulled off the filler cap to add water (engine cold), there would be vaccum. It would take a little effort to pull it off and a suction sound could be heard... kinda like a cork popping sound. Does this have any significance in locating my prob? Just wondering.

Well post when I get the results of the coolant system pressure checker. Thanks again guys.

RonKMiller

Well......there's lots of interesting hypothesis here. But frankly there is no real investigation - just " this is what happened to me"
The whole coolant system is prone to failure as it ages at a number of points.

But like I said, let's look at this from a logical standpoint.

If it is a constant stream of small bubbles it's the seals. Period.
But before we make a conclusive diagnoses let's eliminate ANY other potential causes. And it's FREE. As in NOTHING, ZIP, ZILCH.
Sure beats the hell out of $100 an hour for a "rotary expert".

The next step is to pressurize the system with a dedicated radiator pressure tester which can be rented/borrowed/purchased if need be. AutoZone and probably a few other places will sell/rent you one with a major credit card expecting you to bring it back with no problem at all. They do it as a servce to their customers.

You cannot just take your car to a "radiator shop" expecting any conclusive results since it appears your leak is minor. You need to pressurize the system when it is stone cold for at least 24 hours, sometimes more. Sure, it's a pita to keep walking outside and pumping up the tester as it slowly drops - what you are trying to do is force water out of the system and find it. You may find only a drop or two on the ground, and you'll need to observe it constantly since these drops can evaporate quickly!

If it pisses on the ground you are lucky. The leak is not your O rings, but I doubt it - especially with the miles on your engine.
BUT - it could be your:

1) RADIATOR (BTW - lots of manufacturers use plastic in their radiators - including Mercedes) BrianK's method for detecting leaks is pretty clever but frankly you have to pull it and put it under water and pressure to find out for sure if it is leaking - remember, this is a small leak. The stock radiators are a very weak link on this car.

2) HOSES - God knows there are more than a few suspects here.

3) PRESSURE CAP(s) - We can only hope this is it. With your tester accessories you can check these out in a heartbeat. Test them - don't guess!

4) WATER PUMP - unlikely but still a potential culprit at 80K miles

5) LOW COOLANT SENSOR ON THE WATER PUMP HOUSING - it's on the front of the filler neck and of course is made from plastic!

6) AST - if equipped -what a piece of ****.

7) TURBO COOLANT HOSES - Oh yeah! Last but not least and a VERY likely suspect since they are buried down low. They turn into petrified rubber and leak around the clamps.

So - where is the leak? The only way to know for sure is to pump the sucker up and OBSERVE - Not guess. This is called the scientific method - and it works every time guys........

Once we've found it we can try to fix it.

So, until you "pump it up" for a while you'll never know.

Forget about the CRC until you find the leak - it's there hiding somewhere, and they are sneaky little bastards sometimes..

Brian, if you're not willing or able to do this then you are better off taking it to someone who knows what they are doing. They are few and far between when it comes to rotaries. They also like to sell rebuilds since it is good money. You may still need to go this route but you owe it to yourself to check it out thoroughly before you whip out the ol' checkbook!

Later,

Ron

MILD7

Thanks Ron,

I will attempt to pick up the pressure kit tomorrow... and might as well pick up a radiator cap/AST cap as well. I purchased a filler cap already. A little more history about my car... pretty much bone stock except intake/exhaust. When I bought the car 2 years and 2 months ago, the end tanks on the radiator cracked... as the AST leaked. Fortunately, when I bought the car, it still had a year left on the extended warantee, and the radiator has been replaced free of charge. The AST was replaced as well, but I had to fork out almost 2 bills for that since it wasn't covered. So basically, the radiator and AST are relatively new. I also replaced one of the hose going to the turbos (the small 6" hose underneath the airpump) about 6 months ago, because that develped a leak back then.

I crawled underneathe the car, removed the bottom cover... and no sign of leaks or coolant on the radiator (both on top and bottom). Also inspected the larger hoses to no avail.

I'm beginning to smell a slight hint of coolant under the hood right after I drive it. I'm not sure if it's from the overflow or not.

Like you suggested, the only way to know is to get down and do it right, step by step. My lack of patience at times gets the best of me. Will keep you posted! Thanks!

RonKMiller

Good - I forgot to mention you'll also need to buy a special plastic adaptor, about $20, to fit your AST tank top. You should replace the other turbo hose as well. I'll bet you replaced the uppermost one. The bottom one is harder to get to but you should do it as well. Once we locate the leak (hopefully not your seals) you should also consider replacing ALL your hoses and toss a new thermostat in as well for insurance. This is expensive stuff since it is all custom Mazda hose bends, but then again so are engines! Good luck!

Ron

MILD7

Well, let's see. Finally had time to drop by a Napa parts store today (unfortunately they were closed as well as tomorrow, Sunday). Autozone did not carry the domestic to import adapter for the coolant system pressure tester. I will need to go back Monday after work. Nonetheless something interesting happened today.

Got home from a 20 min... "easy" freeway drive... didn't push the engine at all. Pulled in the garage and popped the hood as usual. Notice some hissing/sizzling sound coming from the filler neck. Apparently the filler cap was leaking. Now, I had just replaced that stupid cap 3 weeks ago... so I'm wondering why it's leaking. I checked the rubber seal when the engine cooled and could not find any cracks, etc. on it. I'm wondering if my engine just got so hot that it caused it to leak. Keep in mind that I just installed a new radiator cap (the one that goes on top of the AST) last week as well.

Another interesting thing is that the aluminum housing that the filler cap sits on was extremely hot tonight. Much more than usual. The sizzling sound I heard was actually the coolant that was leaking from the filler cap boiling. There is also an Allen wrench iron bolt/plug that sits on top of the housing, right next to the filler cap that was extremely hot. Coolant was sizzling off that thing for over 10 min after I shut off the engine. I figured that the bolt/plug was made of iron, which caused that particular point to absorb much more heat, thus boil coolant on contact.

I'm wondering if this really is where my leak is. But something tells me that for some reason my engine was running extra hot tonight... which caused my filler neck cap to leak. I know that there's no sure way to tell until I get that adapter for the testor... which I will do Monday as previously mentioned. Aaaack!!! I know I'm going to lose sleep over this!

Brian

bajaman

Replace the cap.......you are fine, I think, since your engine runs fine and seems to have no other ill effects.
Seems like a lot of people are confusing "smoke" with condensation, in my opinion.......
Anyway, mine did the same thing, seemed like I was always chasing coolant.....add some, leak some, add some, leak some.....
I replaced the cap with a STANT #233 from O'Reilly's and have been fine ever since.
Have hope, young Padewan.....

spooledUP7

Mild7, I think that you have been listining to far in advance to some of the help that has poured (NPI) through this thread. Yes, everyone has a good point, but why would you go a spend the extra dough on a tester when you could by the filler, and pressure cap first? You don't know, (or didn't know) that cap's were not your issue.

Save a buck, buy the caps.

MILD7

I did buy the caps... I picked up the filler cap 3 weeks ago when my car first started leaking... and the radiator cap last week. Even so, still losing coolant (up to a pint a day). That's what puzzled me last night... I'm not sure why my cap was leaking when in fact I just bought it. Like I said previously... the rubber seal on the filler cap still looks brand new and the aluminum neck looks in good condition with now visible cracks or chips. At only $15 I don't see a problem with buying another filler cap, but since it's only 3 weeks old, I'm thinking that my problem lies else where. Appreciate the feedback.

Brian

AdamP

Is there any way you can tell if it is leaking into the rotorhousing buy looking at your plugs?

AdamP

MILD7

Plan on looking at the plugs once I get the cooling system pressurized. I doubt I'll be able to detect coolant in the housings without leaving the system pressurized, since my coolant loss is not severe (that is, if it the culprit is the seals). Will find out soon!

ronarndt

mild7- I went thru the same problem you are experiencing. The advice from RonKMIller is to the point. There are a number of things that could be the problem. Start with the easiest to fix and work your way up. I replaced the AST cap, filler cap, ALL hoses (I think there are 14), low coolant sensor, pressure tested the system, before ruling out everything except bad coolant o rings. If you can find a place that does it, there is a fluorescent dye test that can find even small external coolant leaks. There is also an exhaust gas in coolant test that some shops can do. You can also do a home made exhaust gas in coolant test. Connect a length of tubing to the connection on the neck of the coolant filler cap (not AST cap). Run about 5 feet of this tubing into a clear jug of water and place the end of the tube under the water level. Start the engine when it is cold and observe for bubbles coming out of the tubing. After the engine is warmed up, there should not be any gas or bubbles coming out of the tubing. If there is a steady steam of bubbles, it indicates exhaust gas or compression air/gas mixture is getting past the coolant o rings into the coolant. If the leak is minor, you might try to seal it. I did- was not successful. Got Mazda factory rebuilt block. BTW, mine ran fine, even with the leak, it just could not go very far, cause it would start to pump the coolant into the overflow reservoir, then the low coolant light would come on and it would overheat if not stopped and coolant put back in. Good luck.

MILD7

Thanks Ron,

Well, this is what I've done so far... I've replaced both caps last month. The radiator and AST have been replaced when I bought the car 2 years ago. This week, I borrowed my brother's car so that I could leave the coolant pressure testor on for more than 24 hours. This is what I have found thus far with the coolant pressure testor:

1) Pressurized system to 20lbs... as stated in the FSM
2) Checked pressure periodically to make sure system was
constantly pressurized.
3) Had noticed that pressue would not fall below 17 lbs when
left (ie when I went to work).
4) Pulled the plugs on both rotors after having the system

MILD7

4)Pulled the plugs after having coolant system pressurized for
over 24 hours (both rotors). Noticed no coolant on any plug.
Reinstalled plugs. Started car. Car started fine, no smoke
or smell of coolant.
5)Crawled under and removed plastic bottom/cover to inspect
what I could. Looked at both hoses going to the turbos...
and other hoses... to no avail.

So... I guess I'm going to pick up a mechanics stethoscope next... and leave the pressure tester on longer. Thanks for you help... I find this ******* leak sooner or later!!!

Brian

ronarndt

Brian- One thing occurred to me. I think one of your posts said that when you removed the filler cap after the car had been run, then allowed to cool, that the cap seemed to be under considerable vacuum. This is strange, since if there is a lot of vacuum, it should draw the coolant back from the overflow reservoir into the engine. Did you check to make certain the hoses to the overflow tank are not obstructed or kinked and will allow coolant to be drawn out? I used a large 60 cc syringe to flush and draw coolant thru every friggin hose on the thing to make sure they were open. Since your pressure hold test was good it sounds more like there is some external leak. That's good, since it is less expensive than an engine rebuild, but frustrating to find the leak. Even a miniscule leak will interfere with the proper cycling of the coolant in and out of the overflow tank. I would try to find someone who can do the fluorescent dye leak test. They will put a dye in the coolant, let it run until the engine warms up, then shine a black light on the engine and hoses. Even a small leak will give off a fluorescent green glow. They make a kit to do this, but you would have to buy one for about $150 to use once. Hope you get this fixed. I wracked my brain for over a month before I got mine diagnosed properly- the Mazda dealer was NO help and most of the piston engine mechanics did not do much better. Ron A.

RonKMiller

Well, this is actually very good news and you can just about count on it not being an engine O ring! (although frustrating since it is still hiding somewhere.) Ron A's advice is excellent, and would probably be a great next step re: the dye. Try another 24 hours of pressurizing first though. I would not be surprised if your leak only happens when it is warmed up - all it takes is a pin size hole to cause this much grief, and if in a hot area it could evaporate rapidly. A couple of other places to check that might not be obvious - you'll need an inspection mirror and BRIGHT flashlight: 1) The hose that comes off the top of the block behind the thottle body next to the firewall. It goes to the back of the throttle body. It is commonly used to "burp" the system. 2) the hose UNDER the throttle body. 3) heater hoses on passenger side firewall (doubtful). 4) I still suspect that 2nd turbo hose that you didn't replace before.........it is a real hot spot. Put that stethescope on it and listen for hiss. That's how I found mine.

You may never find it but I am thinking it is definitely a hose somewhere............One sure fire way is to replace all the hoses, it needs to be done anyway with your mileage. I always hate throwing parts at a problem but it IS amazing how sometimes this is the only cure. Think of it as insurance.

MILD7

Well, came home the other day from work (about a 20 min. freeway drive) and popped the hood like usual. For the second time, coolant starts sizzling around the filler cap. I had a hard time believing it was the cap since I just replaced it a month ago. After further investigation... I noticed a a good sized nick on the lip of the filler neck, right where it meets the rubber portion of the cap.

My next question is... where would I find this piece? There's a flange right below the top of the neck. I've checked the mazdatrix catelog (which carries a lot of parts) with no luck. Would the dealer carry this piece? Or would I need to visit a parts dismantler/junk yard in search of one.

I'm pretty sure this is where my leak has been all along. Hopefully I can locate the part, and hopefully, that will cure my car's need to drink water... Thanks for everyone's help and support!

Brian

RonKMiller

Dealer. Prepare to submit an arm and two legs.

If the nick is really small you may want to try to dress it with some emery cloth or a jewelers file. I doubt if this will work, but it's worth a try. Make sure the rubber seal hasn't been chafed or dented - you may want to look at it under a magnifying glass in bright light. Looks like you've found it at last....good for you!
Now about that second turbo hose..............



Later.

ATPRX7

Listen to this! I had the EXACT same problems, where my car burped up all the coolant after shut down, I did the filler neck bubble thing, and it did the same thing as you said, and then I took out my thermostat to inspect it, and all the rubber was chewed up, restricting flow a lot. I replaced the thermostat, changes the 2 caps, and 5,000 miles after it works perfect, not one problem!

Something to think about.

neoanderson

I'm having similar problems but I think mine has to do with a couple newbies putting too much coolant in the system during a recent oil change.

other things:
1) I had a reman put in 6,000 miles ago. (included new h2o pump and thermostat)
2) The temp gauge never goes above half way.
3) The add coolant light has never come on.
4) car starts right up
5) never see the white smoke @ startup
6) took the filler cap off and started it up cold.... coolant quickly started to overflow but before I put the cap on (40 seconds after taking it off and starting it up) I didn't see any bubbles.

symptoms:
1) noticed leaking coming from in front of passenger wheel.
2) noticed a lil' coolant near front of car under fuses near the fans.

I've bought a 13 psi filler cap and a 16 psi AST cap and will be putting those on after work today.

My questions are these:
1) If it is the thermostat are there any sites out there that describe replacing it?
2) what psi was I supposed to get?