I was wondering what could cause high pressure in the cooling system? I'm hoping to get yet another Rx7 that has this problem and the current owner doesn't have a clue as to what it could be

 

Either it's a restriction in the cooling system somewhere, or in my case, my water pump impeller came loose from the shaft and was not turning, causing high pressure. But if I had to guess, I'd say a restriction, more than likely in the radiator. any one else agree?

 

yeah I had the same problem when I received my 7, the coolant would build up and when I was at a stop light it would overflow and spray all over the place, turns out the previous owner never flushed the system and was causing considerable backup. I had to flush the system 7 times, I almost thought i was gunna have to pull the engine, But I doubt yours is anywhere near as bad as mine.

My suggestion, drain and flush the coolant, replace the thermostat with a mazda oem, don't use any auto zone part or anything get it from mazda. Bleed the coolant well and go from there and see if you still have the issue.

If you have already flushed the system recently I would make sure you bled it good and there are no air pockets.

 

alright thanks guys, I'm asking because this car is like 4hrs from me and I want to drive it home

 

Could be an internal coolant seal/seal channel problem. Before you commit to drive the car for 4 hrs, start the car (cold) with the rad cap off and look for air bubbles (not turbulance) in the neck of the rad as it warms up. Good sign of an internal coolant problem.

In any case, I would suggest you reconsider driving the car whatever is causing the overpressure until the problem is determined and corrected.

 

I wasn't planning on driving it back unless me replacing the water pump (I do this with any car) thermostat, and doing a complete flush fixes the problem I just hope it isn't an internal problem because I could get the frame straightened on a different 7 for cheaper then a rebuild

 

1. simple check:
check the cap. when i bought my last Rx-7, the previous owner had put a cap on with the wrong pressure rating and it took me weeks of temperature issues including the damn reservoir exploding all over me one night before i found the cause.

2. the not-so-simple check(s):
you can check the coolant for combustion products and check the combustion chambers for coolant (if you look in through the exhaust ports).

 

What makes you think there is high pressure?
If you start the car with the radiator cap removed, and coolant comes gushing out, it usually indicates a blown coolant seal.

 

I don't have the car yet and I'm trying to figure out if I'll need to tow the car 230 miles home from where it sits, alls the ad on CL says is it's hard to start and once stard it builds to much pressure in the cooling system