my reservoir was just below the "low" mark so I put in antifreeze alone/unmixed to get it to the middle of the resevior. didn't think it would through the mixture off that much but now my car (86 sport na, no engine mods, all shrouds/trays in place) is running up to 3/4 and staying there. it gets there slowly, just as the car warms up. it usually reads about halfway or just below that on the stock gauge. mind you it is raining and only maybe 50-60 degrees out. I do have fairly stiff coilovers but figured I'd ask if too much antifreeze to water ratio could cause this since it coincided. I know what to check after this. fan clutch, air in system, radiator cap, radiator, oil cooler, temp sending unit, thermostat, yada yada (not in that order I know)

 

no straight antifreeze in that amount will not cause that.

my 87 tii was doing the same thing and ended up being the stock fan clutch not moving enough air.

low coolant is either a leak or your burning it.

 

Do you have an airpump? If not... This means you probably only have the alternator/waterpump pulley belt. Your belt may be slipping.

Also, be sure you're not using alcohol-based or methanol-based coolants. As for the water, use soft demineralized water. With outside temperatures being 50°-60° F and getting warmer, you shouldn't even have a 50/50 mix... You should be mixing more demineralized water than coolant.

To check your fan clutch... Warm up your car to normal operating temperature. Turn it off. Now try spinning the clutch fan with your hand. If there is a bit of resistance, it's okay. If it spins freely, as though it is very loose, the fan clutch must be replaced.

 

Did you check the coolant level in the rad?That is pretty well the first thing to check.Belt slippage,worn belts,bad rad cap,bad thermostat,bad pump..list goes on.

 

I have a small coolant leak into engine I think. sweet smell just barely in the exhaust, not crazy. it takes like a year (20-30k miles?) of driving for it to reach the low mark in the reservior. I have an airpump still.

I'm going to put some water in, check my radiator level and see if that does anything. I used the correct antifreeze. my belts and clutch fan is the next thing I will check.