Overheating...kinda
Thread Starter
Pro
Joined: Sep 2004
Posts: 517
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Overheating...kinda
Went on a fairly long trip not too long ago. I recently put in an aluminum radiator, and a Robert Shaw 180 degree thermo stat went in a month or 2 earlier. It will sit right at 180, but then every so often the temp would just shoot up quickly for a little bit before just absolutely plummeting to 180 again (meaning it comes down really fast). Once it got up to about 270 (digital guages) before dropping. No boiling over or anything when it climbs. Doesn't seem to be losing any water. This all happens in probably 30 seconds or so. Ideas?
I'm thinking of maybe drilling 2-3 holes in the thermostat to keep a little water flowing even when it's fully closed. I think I got all of the air out when I changed the radiator. I was thinking sticking thermostat, but it worked fine before putting in the radiator. Would sit around 200-210, as the old radiator couldn't cool it all the way down to the point where it closed.
By the way, it's a 73 with a 355, auto, vortec heads, edelbrock manifold, dewitt's radiator.
I'm thinking of maybe drilling 2-3 holes in the thermostat to keep a little water flowing even when it's fully closed. I think I got all of the air out when I changed the radiator. I was thinking sticking thermostat, but it worked fine before putting in the radiator. Would sit around 200-210, as the old radiator couldn't cool it all the way down to the point where it closed.
By the way, it's a 73 with a 355, auto, vortec heads, edelbrock manifold, dewitt's radiator.
4th Gear
Joined: Jun 2005
Posts: 4
Likes: 0
From: Jackson Michigan
Similar problem
I have a '78 with similar problems...
New radiator, 180 thermostat, and hoses this past summer. No digital gauges, just analog but they're Eckler bought replacements for the originals. Only seems to happen when I get it out on the highway. I've "burped" the radiator several times.. cleaned or replaced corroded connections to the gauges but I get almost the same conditions...
It will jump up almost to the red line... then drop back to normal although in my case it takes a few minutes...
I'm as stumped as you are... anyone have any suggestions?
New radiator, 180 thermostat, and hoses this past summer. No digital gauges, just analog but they're Eckler bought replacements for the originals. Only seems to happen when I get it out on the highway. I've "burped" the radiator several times.. cleaned or replaced corroded connections to the gauges but I get almost the same conditions...
It will jump up almost to the red line... then drop back to normal although in my case it takes a few minutes...
I'm as stumped as you are... anyone have any suggestions?
Advanced
Joined: Dec 2005
Posts: 64
Likes: 0
Me 2
Same thing for me last year. I talked to my neighbor that owns a Vette repair shop (KLJ Corvette). He recommeded replacing the radiator with a aluminum radiator or having the original recored and using a 160 degree thermostat. I had the original radiator recored, put in a 160 degree thermostat and all is well. Winter/spring it runs around 165/170. Summer it runs 180/185. 383 stroker. I recently wrapped my headers so I'm curious to see if that makes a difference this summer.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
OK, if the thing cools down rapidly after a temp spike, that means the Radiator/Fan/Waterpump is working great, thats why the temp goes down so quick, there is cool water coming from the radiator AFTER the THERMOSTAT opens. The symptoms you are having are related to the water/controls ON the motor. Thermostat is a good place to start, make sure ALL the Air is out of the system. I used to do this with the cap on the Prestone Flush kit on the heater hose. You can loosten the heater hose at the manifold with the engine cold and running, water coming out copiously indicates it is clear.The liquid should be at the base of the filler cap if there is one on the Rad. The type without a filler cap on the rad benefit from a filler neck on the top hose, that is the high point on the system so thats where the bubble will be. Get the Pressure cap checked/replaced.
my .02
my .02
Racer
Joined: Dec 2003
Posts: 304
Likes: 0
From: Pasadena Maryland
I had the same problem after I put on my Vortec Heads. I put in a brand new heavy duty four core radiator and still had the same problem. Relocated the Temp Sender after buying the correct one from Lectric Limited and still had the occasional spike. Really scary to see that needle spike like that. I finally drilled two little holes in the thermstat (160Deg) and haven't had a problem since (knock on wood).
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Racer
Joined: May 2004
Posts: 445
Likes: 1
Been having a simular issue as well. I Just finished a cooling system rework. Rebuilt radiator, new water pump, all radiator seals for support and shroud, new hoses, new thermostat. I put in the recommended 195 deg thermostat with a small hole drilled into it, but it had a 160 deg in it and now it runs hotter than before. Used to run around 180-190, today for a first run it was at 210-220. Outside air in the 50's. What did i miss here? I am going to try an burb the system and see if there is trapped air. But I'm thinking it may be the higher deg thermostat
Engine is a 69BB.
Engine is a 69BB.
Melting Slicks
Joined: Jul 2005
Posts: 2,740
Likes: 3
From: Aurora Ontario
For those of you that have the problem on the highway. Do you have front spoilers? They aren't there just for looks they are a must for highway cooling. They direct the air up to the rad. You car will heat up fast on the highway without one.
Jim
Jim
Melting Slicks
Joined: Aug 2003
Posts: 2,135
Likes: 2
From: Dayton Oh
Originally Posted by jdp6000
For those of you that have the problem on the highway. Do you have front spoilers? They aren't there just for looks they are a must for highway cooling. They direct the air up to the rad. You car will heat up fast on the highway without one.
Jim
Jim
also the foam gaskets are important. I ran my 79 a couple of years without them before getting around to replacing. I saw at least a 10*-15* drop in temps afterwards. Guess the GM engineers do know something after all. 