94 SUPER 7

my car does not overheat when driving or anything , but when after my turbo timer shuts off , i can hear my coolant boiling from the overflow tank and i can hear coolant rushing through the lines , and the current of the clow is so strong my ast literally is shaking like its about to blow . i can't figure out what the hell is going on ...have any of you guys had this problem ???

urgirlwantsme

I have the same problem..im gonna keep track of this post to see what it is

TwinTriangles

Might be time for a KOYO...

Trexthe3rd

Check your coolant level when it's hot and compare it to when the car is cold. There shouldn't be too big of a difference.
How much water are you using (50/50 or more)? If the coolant really is boiling over that violently it's one of two reasons. One, too much water as compared to coolant. Two, the pressure in you system is not high enought to prevent boil over.

94 SUPER 7

water level is always full , i always check . i just recently got a rebuild with racing apex seals and street port and everything , so the shop mixed in the coolant .. the thing is it did this befiore my rebuild to , but before it wa seven worse , after driving , i had coolant overflowing from the overflow tank , and i would see apuddle on the floor . i thought that doing the rebuild would fix the problem , but i guess not . I havent had the chance to ask the shop if they know what it is , cuz I really dont want to go back to them anymore . they dont know crap..

TheBigOne

My caddy use to do that. Not that it could be the same but the symptoms are familiar.

Replaced the thermostat.

It helped but the problem was a vacume line was just a weeee bit cracked giving the ECU a wrong signal causing to lean at idle only.

94 SUPER 7

it can't be the thermostat , because if that is malfunctioning , then i'de overheat while driving , and it cant be the radiator either , cuz that would make me overheat also ..its hard to figure out , it just does it i guess when parked , when water is not circulating ?? , but if sounds like its flowing really fast though , you can hear it with the hood closed standing like 30 feet away .. it scares me sometimes , you can literally hear the boiling of the coolant ... but it good be the mixture like trex said , if its mostly water it might do that .. I might have to contact XS tomorrow and ask them , but them foo's are never available to talk on the phone

Trexthe3rd

Back up a bit. If you have coolant spilling out of the overflow tank than there is pressure building in the system somewhere, and it's usually a bad coolant seal. You only mentioned hearing the coolant flow, are you getting over spill from the overflow tank?
Also, when the engine cools down some of the coolant should be pulled back into the system, so it shouldn't be full all the time.
Do you get the low coolant light at all? When the engine is cold, have you looked at the coolant level in the filler neck and the ast? It should be almost at the top all the time.
Also, what is the pressure rating on the cap?

Fritz Flynn

iTrader: (263)

I have owned 8 Fd's and everyone did this so I wouldn't sweat it. My pfc reads over 100c (boiling) everytime I restart the car soon after a hard run so don't worry about it. I think the ast was designed for giving the boiling mixture a safe place to erupt so to speak. If you let your car idle just a bit before shut down and then turn the fans on this will greatly reduce any boiling temps. Remember all that mixture is getting cooled by rad while driving but once motion is stopped the engine is still hot and the heat just gets soaked up by the water causing it to boil.

striker

yeah, this happened with the precat on. now that the downpipe is on there, only on the hottest of hot days does it boil. car is all stock except for downpipe and airbox.

Joker

yeah what he said

Joker

yeah what he ^ said

johnchabin

iTrader: (2)

Wow. And they just rebuilt your motor? Or installed?

Are you running the 0.9 bar cap on the AST? Maybe try the 1.2 or 1.3 bar caps that the RX7 Store sells. You would boil at a higher temp...

http://66.216.67.51/subcatmfgprod.asp?0=352&1=355&2=-1

Good luck.

2-Rotor

I would honestly try changing BOTH radiator/coolant caps first. Then see if the problem persists. Stick with the 0.9 bar cap. (13 pound cap)

2-Rotor

Also keep in mind i mean change your AST cap not the springless cap that tops the thermostat housing.

johnchabin

iTrader: (2)

The 0.9 bar cap was part of a Mazda recall due to bursting coolant lines/engine fires... this has been an often debated topic. From what I've gathered, boiling coolant is not uncommon with the 0.9 bar cap. I personally believe that Mazda took the easiest route to deal with the flaming RX-7 issue, creating a different (although less catastrophic) problem.

If your coolant lines are in good shape, the 1.3 bar cap should be fine. But if your car catches on fire, I will not be held responsible.

Trexthe3rd

There maybe some more helpful info on this thread

Shinobi-X

This is a great thread, I also have a similar problem. It sounds like a jacuzzi in the engine bay, (I heard this was normal.) but sometimes coolant overflows from the overflow tank... Car has 100K miles on it, with stock radiator and hoses. (Yeah, I know it needs a vac. hose job, but it's snowing. )

94 SUPER 7

hehe jacuzzi =P , thats exactly what my engine bay sounds like after driving . bubbles lot's of bubbles

jeff48

All I got to add is gloom. The ONLY time any of my 7s made those noises were when the O ring was going south. Check for this soon by doing the following:
1. remove radiator cap
2. start car bring it up to operating temp.
3. look into filler tube

if you see a stream of tiny bubbles you may need to start saving up for a new engine.....or in your case ....a quick telephone call to your rebuilder.

Tom93R1

iTrader: (2)

My 7 did this until I replaced my radiator cap. It turned out I had a pressure cap on the filler neck and that didnt properly seal. When I shut off the car it would de-pressurize through that cap and start to boil after a couple minutes.

mecman

iTrader: (11)

My Touring did the samething on a hot summer day.

A downpipe, flush with new coolant, and a fan mod reduced the heat and made that go away.

Someday I'll have to add a Fluidyne....

bliffle

Yup - had the same experience with a couple cars. ANY leak in the water system can cause this because when the pressure reduces the boiling point drops, and Voila! I've had it happen with a radiator hose that leaked slightly: the water stayed hot long enough for a pressure relief thru a slow leak in the hose connection, then bubbles.

B

bliffle

Yup - had the same experience with a couple cars. ANY leak in the water system can cause this because when the pressure reduces the boiling point drops, and Voila! I've had it happen with a radiator hose that leaked slightly: the water stayed hot long enough for a pressure relief thru a slow leak in the hose connection, then bubbles.

B

bliffle

Yup - had the same experience with a couple cars. ANY leak in the water system can cause this because when the pressure reduces the boiling point drops, and Voila! I've had it happen with a radiator hose that leaked slightly: the water stayed hot long enough for a pressure relief thru a slow leak in the hose connection, then bubbles.

B