Coolant Vacuum Problem

Hi, I'm new here.
I have an '86 RX-7 with what seems to be a coolant leak except there isn’t a leak. When the engine warms up the coolant expands into the overflow reservoir, but when the engine cools again, none of the coolant returns to the engine. It seems like I have a leak somewhere in the overflow tank or a leak in the system that can hold pressure but not vacuum. Does anyone have any idea what this could be?
Thnx

I just had another thought - could it be possible that combustion gasses could be leaking into the coolant? The coolant looks like hell but I assumed that was because it had been sitting in a dealers lot for a long time. Maybe its oil or combustion gasses.
If anyone knows how to test for these problems, I'de really like to know.
thnx

Try flushing the coolant system. This may fix the problem.

start the car, let it idle, take off the radiator cap, and see if the coolant is bubbling..


Changing all the fluids is a ritual of mine everytime i buy another RX. I would go buy 3 quarts of redline diff/trans fluid (1.3 quarts for diff, 1.6 quarts for trans) 5 quarts of a good conventional oil ( i use valvoline 20w50 in my turbos and 10w40 in my N/A cars) and gallon of the good prestone anti freeze with full metal protection.... and a bottle of redline water wetter..

the best "recipe" for your coolant is:

with you car completely cold (several hours since it has run) flush the entire sytem completely. Maybe use a flush kit, you may have coolant sludge deposits through-out the engine.. during tear-downs i always find some in the rotor housings near the intake.... then the cust is like, i gave it good maintenance, i wonder why it needs rebuilt.... So i ask if it ran warm....

leave the radiator plug and caps (radiator & filler neck & overflow) off for a while to allow the system to dry out a little bit.. I blow through mine with a small amount of air pressure from my compressor... (usually i unplug it, and when the pressure gets low, i empty the tank)

Put all the caps back on but the filler cap

ADD:
One bottle Redline Water Wetter
15% prestone glycol
remainder with distilled water from Walmart or a grocery.
(buy it off the shelf so it is at room temp)


This way you start with a completely clear coolant. do not use tap water.. there may be things in your tap water which can react with some or all of the materials in your coolant system (aluminum, steel, rubber, brass, plastic etc)

after you dump all this in the car, and it is full, start it, let it idle and keep filling the water neck, it may want some more water after you start the car... make sure the heater is on.


Drive it
check for bubbles or color changes.

if none drive it for a few days check periodically for drastic color changes and for bubbles...

Also, check your spark plugs. are they clean? Like steam cleaned? or a bit dingy, or blackened?

You may as well change your spark plugs while you are doing all of this other maintenance..

let us know if you have any other questions... welcome to the RX world!

Nice sig Dayna240sx. :bigthumb:

Wow, thanks for the help. hope this fixes it.

ps - that sig rocks

well... I have a bunch of bubbles in the coolant. So what now, is my only option an engine rebuild?

Im not a big car person and dont know much about rebuilding an engine. I dont have enough money to even come close to getting a new engine. Having someone else rebuild it would probably be too expensive also. The dealer where I bought the car refused to even admit that there was a problem so they arent going to do anything about it. :twak:


ugh. So anyway, what do you think my options are?