I have never had any issues with cooling since switching to an aluminum radiator until now. I have just completed a rebuild (rings, bearings, cam) on a motor that had under 10K since the last rebuild. When I first start the car it will warm up and go to 220 degF for about a minute and then the cooling system will kick in and bring everything to normal. I have never had to do anything special in the past when filling with coolant on this car. I replaced the t-stat and even checked the new one on the stove and it opened right at 180 degF as marked. I took extra care to top of the radiator after starting the car and have the correct level in the overflow. Is there still air in the system or could it be that the temp sender off of the head is seeing the heat before the t-stat in the manifold? I don't think this is a big issue but it is odd that the cooling system is behaving different than before. The only time I have seen similar is when a t-stat was sticking, but I know this is not the case now. Any ideas?


Hold on here because I don't think that anyone would have guessed this answer. The short answer is carb tuning, specifically the Holley Power Valve.

With my cam change I crossed the threshold on the power valve in idle. The cam was not pulling quite the vacuum of the old one (I stepped from a comp cams Magnum 270 @ ~0.470 lift to comp cams XE274H @ ~0.490 lift). This lower vacuum caused the power valve to be at least partially open at idle which was dumping gas into the manifold and cooling it off from evaporation. I swapped from the 6.5" valve to a 3.5" valve. After that I needed to fine tune the carb jets but that is another topic. Cooling and temp oddity explained.


[Modified by PatG, 11:01 AM 3/27/2004]

 

Air isn't uncommon... what you might try to do is take the cap off when cold and start it up and let it run...that may help it burp out any air in it.

 

......I've heard that rebuilt motors will run hotter.....also, the T-stat doesn't immediately open at 180...it might take 10 or more degrees to open....you could try a 170 to see if that reduces the peak temp at startup.......

.......otherwise it's checking the water as above.......check for leaks at hose connections or the radiator and/or expansion cap........also check if water is coming out of the overflow......

Keep us posted :cheers:

 

sounds like you still have some air in your system for sure. My daily driver has the same problem. The heat goes way up on the guage then comes down to normal. Then its fine untill I shut it off and let it sit. I can hear the overflow tank bubbling up. let it cool and the same thing happens.

This happened after I took a coolant hose off the throttle body that was leaking. I put the new hose on and just topped off the tank , so im sure there is air in the system.

Im not 100% on your situation but you may want to flush the radiator / cooling system out and refill. I have also heard that jacking up the front of the car can make a difference because the air will have a better chance of escaping. Thats my suggestion anyway, but it sounds like its for sure air trapped in there somewhere. :cheers:

 

:iagree:

 

:iagree: Instead of jacking the front up, I just park pointed uphill on my driveway (which is pretty steep) to get the air out.

Hank

 

Thanks for the replies. I have to think that there is some air in the system. I will try the driveway trick and see if I can top it off some more. I know everything is clean, the radiator is only a few years old and I just went through a complete refill of the system after the rebuild.

 

When filling the cooling system, turn the heater on to full hot.

You also might want to drill a really small hole in the t-stat

 

bump,

Solved, read the explanation in the first post.

 

It amazes me how frequently people will reply to a post that they have not even read completely. Go figure.