Just recently I've been noticeing some cooling issues with my car (built bottom end, APS TT G35 coupe).

It all started when the temp dropped, and I noticed my heater takes FOREVER to heat up - 12-15 minutes. My coolant heats up fine, right to ~80 degrees C. I was thinking, at first, I was either low on anti freeze, or that my thermostat was sticking open. I opened the cap on my Koyo radiator and the level looks fine.

However, ever since I popped the cap, now the car still takes forever for the heater to get warm, but usually before the heater gets warm the temp guage spikes. My Cypher showed temps near 120 degrees C for ~10 seconds, then it dropped back down to 80 degrees and my heater started blowing out warm air.

Is it possible that I let an air bubble in to the system when I opened the cap?

Also, at idle the car blows cold air, although the coolant temp doesn't drop at all. If it were a stuck thermostat would the coolant temp stay constant like it is?

Thanks,

Kevin

 

Try opening the cap and squeezing the upper radiator hose - see if air bubbles out, or level drops. that will show you if you have air in the system.

 

There is a procedure for removing the bubbles from the cooling system in this link.

http://crackaddict.com/~flynn/howtos...amco.howto.htm

 

You have an air bubble. Here's what worked for me. When the car is dead cold, open the breather screw in the back heater hose line. Take a small (very small) funnel and pour in some 50/50 coolant unit its full. Run the car normally. If it didn't fix the problem, repeat the process (car must be dead cold to do). When I swapped out my radiator, I had to do this about 4 times but now its perfect.

 

Can also be caused by a low temp thermostat.

 

One would think that the OP would know whether or not his car had a low temp thermostat.



"I'm just sayin..."

 

+1

 

If the air bubles out thing didn't work i would suspect the thermostat.

 

Thanks for the advice. It is a stock thermostat. I'll try to see if I can squeeze some bubbles out of it!

 

To get air bubbles out, this is the way i do it. I run the car cold with the radiator cap off, then i squeeze the top and bottom radiator hose that will "burp" the cooling system.

 

OK, the car was low on coolant. I added a little bit of distilled water and it now heats up MUCH faster, and the temp guage hasn't raised a single time.

I didn't realize that the coolant was supposed to be level with the overflow hose. Having a Koyo radiator the fill neck is (from what I remember) a bit longer then stock, and my level was right to the top of the radiator, but NOT in to the neck.

I added water, put the cap back on, started the car, idled it, and once it got warm I revved it to 3000RPM for 10 seconds. I then let it all cool down and popped the cap off and refilled the radiator. I did this three times, and the third I didn't need anymore water. I also, in between each filling, drove the car around my neighborhood and let it sit both forwards and backwards on my inclined driveway.

The 'big' problem I have stems from the APS TT and the fact that my heater bleeder fitting has been removed and not reinstalled.

The car still blows cold air at idle, but not ice cold like it used to. I'm thinking that my thermostat is stuck open, and I'm totally fine with that.

 

A stuck open thermostat will NOT cause the heater to blow cold. You have air in the system.

 

I was told that if the thermostat was stuck open it could cause the air to not be as hot as under load due to the fact that engine is being cooled down more then if a thermostat was installed. Is that incorrect?

 

When a thermostat is stuck open, most cars tend to over heat. This is because the coolant flows too rapidly and does not spend enough time in the radiator releasing heat. This is not, however, true for all cars as some run cooler with no thermostat. Even the ones that run cooler will still blow ho air because the coolant is at least 140-150°.

 

I see. I checked again last night before I went to bed and added a little bit more water. I'll keep checking it for the next week or so.

 

Just keep re-checking and keep an eye out on that reservoir. I don't think your thermostat is stuck, that usually happens with high mileage corroded ones. Good luck

 

keep this updated if you can.. I just got my car out the shop with a new engine and I am having the same problem with the "Cold on idle" issue.

I checked my coolant fluids and they "appear" to be fine..

will check for air bubble this afternoon..

thanks

 

What should I be looking for in my reservoir? It isn't marked with a high/low like the OEM reservoir is. I filled it about 2/3rds of the way with distilled water and it seems to be fine.

I've added a small amount more water to the radiator too, but not much at all. The heater is still heating up quickly again, but it still drops in temp at idle. However, it isn't blowing cold air, it's just not hot air.

 

You can also open your radiator cap when the vehicle is cold and check the fluid that way. I highly recommend using some type of bleeder in the cooling system though, it is very effective.

Have you upgraded your radiator cap also? If you haven't I suggest doing it.

 

I have been checking under the radiator cap. Following the service manual it said to make sure the radiator is filled up to the overflow hose, and then fill the resorvoir up to the 'max' line. Well, I don't have a 'max' line to fill to.

Also, as stated above, I don't have a manual bleed off valve, as the APS TT eliminates it. I do believe the system is designed to bleed itself, based off of what I have read, and the fact that when we first started the car up and shut if off with the new motor and TT would could hear air escaping through the resorvoir.

I have the Nismo radiator cap.