Please help diagnose, give me some direction here...

Finished the install on the short shifter...

Car warms up to operating temp
Drive 5 miles
Stop at Sears 20 minutes

Start the car and the coolant light comes on immediately!
Shut the car off immediately and pop the hood. NO coolant under the car. ALL hoses leak free. I pull the pressure release lever on the AST and hear coolant being sucked from the overfill tank. Car cools 5 mintues...I pop the filler cap...coolant level about 1 inch below the filler neck.

Start the car, turn the fans on, drive realllly slow home with my eye on the temp the whole way.

In the garage car cools with fans and external fan for 10 minutes. Open filler cap...NO COOLANT there...AST is full...overflow is full.

Help..?

Thanks!

 

You might have to fear the worse. . . My engine had similar problems. Turn car on, drive around awhile, coolant fills up in the overflow and BRRRRR add coolant. . .Move coolant from overflow to waterpump inlet. . . 100 miles later, brrrrr add coolant. . . got annoying. SO I tried the usual, check for leaks (none except for when my overflow tank, actually, overflowed), changed rad cap, no apparent coolant smell inside. . I didnt know what was going on until I heard that the waterjacket that surrounds the engine (or rather is part of hte engine) possibly cracked, and coolant was being mixed with exhaust, forcing the coolant out of the system and exhaust into the cooling system. . . Check if your coolant looks dark. . . so, after a year of doing the whole "put coolant back into engine business" I gave up, and got another engine. . .BTW I have a 87 TII with a 89 TII Engine

 

Ok that scared me...drained some coolant...looks like its brand new...

 

i had the same problem with my 86 n/a. Well it ended up being my oil cooler lines were busted but you might just have some air in the raditor.

 

If it's the exhaust getting into the coolant, it wouldn't have anything to do with whether or not the car was warmed up or not.. Maybe you can take off the filler cap and start it.. see if bubbles come up.. If bubbles come up when it's cold and running, it sounds like exhaust.. take a whiff.

Else, it seems that it only leaks out when it's hot.. In which case, it's more of a pressure issue.. Are your pressure caps in good condition/new?

-Tesla

 

Exhaust doesn't smell like coolant...made me kinda high though

Anyway, my caps are old. Going to eliminate the AST this weekend and drain my coolant as well.

See how it does after a thorough inspection of hoses and such.

 

I had this problem early on this year. My coolant light kept coming on even if I had coolant in all tanks...and I had no leaks. This is what i did.

Cheapest:
Replaced all my caps

Not so cheap:
Replaced the coolant sensor wiring ($70). I had it done at the shop. Apparently, mine shorted out. This may or may not apply in your case.

Most Expensive:
Flush and Fill. I had it done at the shop too because I got tired of messing with the coolant. I read somewhere in the forum that the cooling system needs to be burped for a long time. Otherwise you'll be hearing gurgling sounds when you shut off the car after a short, fun-filled drive. That freaked the crap out of me. I thought my engine was gonna blow. My mechanic buddy used an additive made by BG. This stuff is cool. There are three parts...one additive plugs all leaks, next is a chemical to do the flush, and last an additive ,like water wetter, added with the coolant to run it cooler.

While I was doing all these, I also decided to do the fan mod. I bought a fan thermostat from the local auto parts store for $25 bucks. It's an adjustable relay with a probe that you stick on the fins of the radiator, then wired to the electric fan and the ignition. I set it for 195F (Fan turns on full) and off at 185F. I drove my car around all day for 100+ miles today, in traffic, my temp on my water guage was 182F-196F. No problems with the coolant either. When I shut off the car, the fan stay on for 30seconds to 1 minute until it's back down to 185F.

Hope this helps, I had a lot of good luck with this.
Laters,
Jason
93 Silver Touring w/ 106K (Yikes!)

 

what effect would adding a higher pressure cap have?

 

If the rad cap is bad or the seal is cracked in the cap, then the hot coolant moves past the cap and into the overflow tank. Sometimes when it cools off, the coolant flows back (siphon) to the rad. Change the cap (use the OEM) They cost about $12.00

Mazdatrix.com can supply by mail.

It solved my problem. There was nothing else wrong. Runs cool now

 

I had almost the same problem with my car... It ended up splitting the upper radiator hose. Check that hose out, you might need to remove the airbox. Just make sure it doesn't split then you start driving it....

 

Went ahead and did the AST mod. So far everything is running great and no ill effects felt with the AST gone.

Thanks for all the info!

 

ok this may be a dumb question, but i am new a new 7 owner and well what the the heck are you guys talking about when you refer to the AST ??

 

AST = Air Separation Tank, it is part of the OEM cooling system. It is made of black plastic and has a pressure cap on top (attached to the intercooler). The OE ASTs have been known to fail and cause immediate loss of coolant and create an overheat situation leading to engine failure.

This is one of the first reliability mods one should perform on an FD.

Two mods that people do. One eliminate it. Or two, replace it with an aftermarket aluminum version.

See this site for more:
http://www.rx7turboturbo.com/robrobi...olant_tank.htm

I went with the aluminum aftermarket unit, but I can't tell you what the best solution is.

 

oh ok that helps.. thanks.. least i know that i dont have to worry about that then with my 84gs

 

is the cap on the ast supposed to be a certain pressure level? I'm asking so i know what to buy if i replace the caps.

 

Stock cap is .9 bar or 13 lbs.

 

I know the radiator cap is 13 lbs. Is the AST supposed to be 13 lbs too? Mine doesn't seem to be a pressurized cap on the AST.

 

on a 3rd gen the radiator filler cap is unlimited but the AST is 13.

It was 13 on the 2nd gens as well.

 

just do a pressure test it could be and sounds like a water gallery seal in the engine, does the engine ide rough on start up, check for excess steam from exhaust and check upper and lower hoses when u do pressure test be sure to reove pluges from motor and keep visual for water leaks from plug holes.