areexseven888

Greetings!
I just purchased a 1993 FD rx7 and had a question regarding the cooling system. I did my best and managed to read most of the coolant related threads but nothing really answers my issue. The background is that I'm having issues with the coolant being pushed into the overflow and not coming back. I went ahead and replaced all the caps, thermostat, radiator, radiator hose, and AST line. The AST unit is a tripoint and I'm pretty sure it's in good condition.

My issue is that though I've been bleeding it using the guides online, I seem to still get bubbles in my system and my overflow gushes coolant out without sucking it back in. When the system is cold, there's still a seal as I can hear air being sucked in when I open the filler cap. Also, I'm not sure if this matters but the radiator hose is stiff on both the lower and upper. Another issue that I find puzzling is that when I squeeze the radiator hose, air doesn't come out but every time I shut off the car with the lisele funnel, air keeps coming out. I've been turning on and off the car and have gone through 1.5 gallons of fluid burping it this way. It doesn't seem to stop which is causing me to believe that maybe the coolant seals are bad and allowing exhaust gas into the cooling system. Also, when I drive, the cooling system is completely fine and is at a constant 84c but when I stop and turn off the car for a quick run to the store, the temp seems to rise. The pattern of the gauge temp goes from low 90c back to 84, quickly back up to mid 90c and quickly back down to high 80, low 90s. This leads me to think that it has something to do with air being introduced into the system. I have not pressure tested it nor have I checked my spark plugs yet. The car did just have the spark plugs and compression done by RRR last week and they didn't mention anything about coolant. Any ideas?

Taka

Sgtblue

iTrader: (16)

I think you've pretty much answered your own question as to the probable cause of the symtoms. I think your next move is that pressure test.
----> https://www.rx7club.com/new-member-r...oblem-1032258/

RCCAZ 1

iTrader: (10)

Ok, not meaning to give you HOPE, but here goes. I chased my tail like you for nearly 6 months a few years ago and finally found MY problem. I did everything you mentioned and MORE, so don't quite give up hope yet! Just because you replaced all caps does NOT mean that the caps are good. Get a pressure tester with an adapter that allows you to test your pressure cap and test it. Make sure if it's a 13 lb cap that it cracks "close" to 13 lbs and HOLDS pressure. Make sure that the non-pressure cap has a good seal as well and can hold pressure if you apply pressure. My BRAND NEW 13 lb 'Stant' cap from NAPA would crack at about 11 lbs, then drop off to 9 psi very quickly, (within a minute or two), which is not good. Take the tester to the store with you and have them pull caps off the shelf and test until you find one that passes to your satisfaction. Also, I avoid any pressure cap with the red "relief" lever in the middle, since these levers are a failure point that often leads to bad caps.

If the engine is going, prior to start-up your plugs will be pretty "moist" from coolant. Another tell tale sign that the end if near is if your engine "chugs" or hard starts and sounds like it's misfiring badly or only running on one rotor for the first few seconds of startup. Once you get to that point, it's time to find a cherry picker. Until then, keep digging.

areexseven888

Thank you RCCAZ 1. My issue right now is why bubbles do not come out of the lisele funnel when the motor is on but comes out when the motor is turned off. Another issue is that it's never ending! Maybe bringing out my trusty cherry picker is in my near future!

Sgtblue

iTrader: (16)

^If it is a failed coolant seal, it might depend on where the failure is. If it's near a rotor's intake phase, coolant tends bleed into the chamber and foul combustion. You get a lumpy idle on cold start. If it's near compression, when you shut down, the air/fuel mix could be bleeding into the coolant system...so you see bubbles on shut-down.
As I mentioned in the link, there are many symtoms that can be explained by other causes. But the more symtoms you have in combination...the more likely it's a coolant seal failure.

bobsrx795

Just dealt with this bled and bled over and over kept getting bubbles. If it is a seal it will also try to push coast out after heat up or on shut off.

areexseven888

So what did yours turn out to be? The seal?

samjaza78

Piston experience, but possibly relevant- when the head on my Nissan cracked, it cracked from the exhaust valve to the cooling jacket. No white smoke out of the tailpipe, but temps would randomly skyrocket- almost like a failed thermostat. I'd pull over, shut the truck off, and ease pressure off the cooling system, which would fill the overflow tank pretty much completely. Start, idle, and feed the coolant back in, which led to the occasional violent bubble explosion as the thermostat attempted to compensate for the pressure and temperature changes.

You, obviously, do not have that level of issue. But swinging by a shop and asking for an exhaust gas test on your cooling system would be the final answer.

areexseven888

Yeah, I definitely need to get it checked out. Just did a pressure test and it would lose all pressure in 40mins. I'm way over my head at the moment.

Sgtblue

iTrader: (16)

Sorry, but honestly at this point IMHO, a test for hydrocarbons in the coolant is redundant. You've lost a coolant seal. Or maybe more accurately...the previous owner lost it.
There are rebuild videos available on-line, and the FSM available for free. But you should be an experienced wrench turner. Otherwise I'd look for the nearest rotary specialty shop nearest you. Again, sorry it's not better news.

areexseven888

I'm definitely going to take it to a shop but beforehand, I'm going to put coolant dye inside the coolant and try and check for any leaks. I only say this because even pumping it, I can still start the car fine. I'll also need to check the plugs.

samjaza78

If you really want to go over it with a fine tooth comb, actually spend the 20 bucks on a head gasket test kit- the dye set. It'll work on a rotary cooling seal the same way.