Rotarded

Let me start this thread by saying I am a Service Director at a dealership, and also do tech work on the side.I am no Newbie and I have searched and researched for over a week. So, that being said, I would appreciate replies that explain a bit more than "time for a new engine".

I started venting a small amount of coolant out of the overflow after shut-down about 3 weeks ago, right after I swapped turbos.I would have to add about 6-8 oz of coolant every other time I'd start the car completely cold. I have never seen any white smoke of smelled coolant or coolant smoke.

I have been watching my coolant temps, via the PFC, like a hawk and have never seen temps above 92 while driving.

Last week I replaced all 3 coolant hoses attached to the AST as well as the AST cap. No change in symptoms..

This morning, on my way to work, the temps started to shoot up and the coolant buzzer sounded. I shut the car down and coasted into a parking lot. The temp peaked at 104 and the coolant was being purged from the overflow.

I let the car cool for 3 hours.

After a couple of attempts to fill and burp the coolant with the same results, noting that the radiator(stock) was still cool to the touch , I replaced the thermostat and filled and verified that the water pump was working and no external leaks form housing or hoses. Once again, it vented from the overflow.

I let the car cool for 2 hours.

I replaced the coolant filler neck cap and filled. The temps stabilized at 89 degrees at idle for 10 mins. I started on my way home. Within 400 yards the temps rose to 94 and the coolant light/buzzer sounded. I shut down and coasted into a parking lot. Venting from the overflow.

I let the car cool for 1.5 hours, filled and burped. I drove the car 1.5 miles home with the temps stabilized at 87 degrees and shut it down for 45 mins.

I checked the oil filler cap and had no coolant/oil foam. I topped off and idled for 5 mins at 89 degrees. Fans checked and both functioning normally. Test drove around the neighborhood until the temps began to slowly rise to 94. I opened the hood and saw steam venting from the AST cap. The overflow DID NOT VENT.

I let the car cool for 1 hour noting that I had added a lot of water to the system, went and bought some more coolant.

I added some coolant at the filler neck and idled at a steady 91 degrees for 10 mins. I took a test drive for about 3 miles when I noted the temps creeping again adn then the coolant light/buzzer came on. I coasted a majority of the way back to my garage with the water temps at peaked at 104. I looked underneath and saw that I had vented only a very small amount (1/4 cup) vented out of the overflow.

I let the car cool for 1 hour. I looked underneath to see my overflow completely empty, and the floor dry??????

I started the car and idled. The temps rose normally to 91 degrees and stabilized for 3 mins. The temps started to climb quickly and I shut it down at 100. I get out to find the coolant oveflow NOW FILLED!

Can anyone tell me what the hell is going on?? Please help!

Mike

BigIslandSevens

iTrader: (4)

Soo. your a service director? Have you tried doing a pressure test on the cooling system? Sounds like you just are stating the obvious....coolant vents out! Figure out where the pressure that is causing the coolant to overflow is coming from. Have you tried asking one of your mechanics about the problem? Get the proper tools for diagnosing coolant problems. As helpfull as this forum CAN be, getting your hands dirty is usually the only way to figure it out. I'm not going to tell you what I think the problem is cause I don't have the car in front of me to do a pressure test on the cooling system!! I am a mechanic and can only tell you that you have to perform the BASIC tests before anything!! It will tell you so much... whether your looking in the correct area or not. Not trying to be mean so please don't get all defensive. but this is why most people work on their own cars or take them to a Rotary speacialist instead of letting the dealerships work on them. Sorry!, but that's the truth. You should be able to figure it out with just a few tests.(Hell, if all else fails......take it to the RX7 store. They are in Ohio, and on this forum. Plus I hear they know what their doing!Hahaha!) Gooood luck!!

mp5

iTrader: (3)

Mike,did you replace ALL of the hoses in ths coolant system? ie even the small ones running from the throttle body?

when you fill with coolant are you leaving the throttle body hose OFF to vent the last air pocket? did you "duct" your IC intake to feed cooler air to your radiator? and what % of water/coolant are you running?

Yes, I did theese Carl..... shuddup already!!

Ok now, where is the leak at? its somewhere right? your radiator possibly? its just a systematic process to find it now.
FWIW I did a pressure test on my car(left overnight) and i showed NO drop off at all!! even though I was having horrible cooling issues driving the car just a few miles.
Its also a misnomer regarding "no white puff of smoke
on startup so my coolant seals are ok" because I did,nt have any smoke too and my car leaked like a sieve, which I beleive now to be the coolant seals.

The gremlins seem to come out to play when everything has warmed up and expansion of the engine has taken place(and the defecit of a coolant seal to seal ) making it a little tougher to diagnose when the leak is very small
I only arrived at that conclusion because there was simply no other coolant related parts to replace on my car.

I think a upgraded radiator would be your next step because it "forces" you to get in there and replace hard to see hoses also your asking a lot from the radiator now its playing second fiddle behind the IC.
poseur

Rotarded

BigIslandSevens,

1. I did neglect to mention that I have pressure tested the system.

2. I work at a Saturn dealership. My ASE Master and Mazda Master (pre-FD), politely refuses to work on my car, but does supply me with some diagnosis help.

3. The RX-7store is where I help out as a part-time tech.

4. I would never take my car to a Mazda dealership.


Thanks for the reply, no offense taken. This is my curse!!

legal-z

is the hose to your overflow tank piched or creased in any way? i had it happen to me and when the coolant expanded it would go into the overflow tank but when the coolant would contract it would cause vacuum in the hose and completely collapse the area where the hose was pinched and not allow any fluid through. so every day or two my buzzer would go off because the system never recaptured coolant from the overflow. just something to check.

johnchabin

iTrader: (2)

Have you changed the thermostat?

If no, change it.

If yes, change it. You may have gotten a defective one. Take it out and boil it with a thermometer in the water. Note when it opens and opens all the way.

johnchabin

iTrader: (2)

Oh, I read your first post again and see that you did replace the thermostat. I'd still check it, though.

Did you use the Mazda thermostat or a knock-off?

turbojeff

iTrader: (30)

Sound like you need a new engine.

I assume you have the correct cap on the water neck (flat internally) and the pressure cap on the AST (with the spring).

Pressure tests only build up 14psi or so. The coolant o-ring is under thousands of psi. When the motor starts to go you'll get symptoms like you describe, a pressure test doesn't catch it until it gets really bad.

Fill the coolant system, start the car up totally cold and look for "little bubbles" coming out of the water neck with the cap off.

Also there is a test that tests for CO in the coolant I think. This is a sure way to find out if the exhaust is getting in the coolant.

Save for new motor in the mean time.

Good luck

rajeevx7

iTrader: (11)

to be burning that much coolant, there should be a very noticable amount of smoke on start up, if the o ring is bad.
ive heard about a hairline crack at the top of the overflow tank that wont eject coolant untill the coolant gets hot and expands to that level. like i said, it is hairline so people rarely find it, but remedy the problem with a new overflow tank.

also, check what turbojeff said about the bubbles rising, you do sound like you already know what you are talking about.
good luck, raj

Snook

iTrader: (12)

The car doesn't have to smoke out of the exhaust to have coolant seal failure. You have tested mostly everything so don't try to deny it any more. Start saving and make sure the next engine is built up right.

good luck
-SNook

Rotarded

Doh! I cannot deny, that I will NOT need an engine.

Well, after heading to the track with Kyle (nocab72) this morning at 7:30 am, I noticed he had a small tear in the hose that attaches at the AST cap. As I was showing him I realized, **** my hoses are wrong.

It seems my trust in my stepson, to do the most simple tasks, came back to bite me. He put the AST hoses on incorrectly. How in the hell could he screw up? The bottom one to the radiator is the one he got right!

I drove 50 minutes home, switched the hoses, topped off and tested. ALL IS GOOD!!

I proceded to drive 50 minutes back to the track, tech'd, and ran one time.

Ambient temp 84. Coolant temp 94. Heatsoaked as a motherf*%er, missed 3rd gear:

13.8 at 101 mph. My worst time to date!!BUT MY CAR LIVES!!!!

BigIslandSevens

iTrader: (4)

Cool!!! Glad to hear I didn't make you mad at me! What did the test show?... I see TurboJeff's reply and agree. Do you get bubbles in the neck while it's running? Also I've had the overflow tank leak where the upper neck goes into the tank. These cars are a bitch to get burped out. A trick I found on here is to remove the hose from the top of the TB, and fill the system until it comes out that hose. Plug it back in and top off the neck. Run it for a few mins. with the heater on. Let cool , top off,. repeat. Also , I've seen alot of liitle hard to find leaks. I've found them recently by buying a die kit from the auto parts store. You add a certain amonut/ per coolant capacity. Run the vehicle so the thermostat open and flows coolant threw the system. Then take the BLACK light,(usualy with kit) and shine it at ALL the hoses in the cooling system.(14 or so). The leaks will show up as a glowing fluid. Shows the leaks in the radiator cores (Very hard to find,, the ones in between the fins!) Try this if you have no luck. You can easly flush all the die out if you like but it helps in the future and doesn't hurt the engine. Good luck man !! Hope I helped you out a little. .. P.S. That's cool that you help out Rx7 store. Makes me think you'll get it soon.

Rotarded

BigIslandSevens,

You posted, literally a split second, after I posted the happy ending!

BigIslandSevens

iTrader: (4)

WOOOO!!HOOOO!!! Don't try to blame the boy for your mistakes!HAHAHAHA!!! Take it like a man. Just kidding glad you got it figured out!!!! ...And I just spilled my brain on the cooling system to you!!HA!! Good job !!!

Rotarded

Postscript: I believe the original overflow venting was caused by the filler neck cap. I somehow corrected that, and created a monster in the process.

Rotarded

I just did a silicone hose job with his help. I told him at least 25 times "always remove one at a time when you are replacing more than one hose".

Guess I didn't tatoo it on his forehead, so I deserve that!

BigIslandSevens

iTrader: (4)

I take digital pics of ANYTHING I think I mayy forget or screw up! It's saved me recently on a boost issue!! Switched 2 hoses Press. tank and UIM check valve hose
! Hey!!! We were ALL there at one point in time!! That's the only way you/he'll/we'll learn. I'm willing to bet He nor you ever hook those hoses up incorrectly again! Haha!! You always remeber those types of goofs!

Snook

iTrader: (12)

right on man!
it's not like I wanted you to have a bad engine but you were describing one....nobody would have guessed those hoses were wrong lol....no wonder the car was shitting coolant

Sweet deal