Radiator blues
Thread Starter
Instructor
Joined: Aug 2002
Posts: 231
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From: Tucson AZ
Radiator blues
Just installed a Dewitt's radiator in my daily driver. I replaced the thermostat about a year ago because the temp kept rising to over 210 (running with a 383 & a mild cam) then rapidly dropping down after about a minute to the mark between 100 and 210. I replaced the thermo with no change. I then noticed my radiator was leaking slightly, and limped along with it until I got the new one ordered. I put in the aluminum radiator this weekend hoping that I'd see a change, and I did. The temp now goes higher before dropping like it did before, and the temp seems to run closer to 200 for a while particularly at speeds over 55, and drops down to slightly below the mark indicated above when traveling at lower speeds. I noticed a large opening between the rad support and the radiator, so I sealed it temporarily to see if that would help. No luck. When I refilled the radiator, I pulled the heater hose off the top of the intake, and then put my handy mighty vac on it to make sure that there was fluid in the thermo housing. Not sure what the issue is. I'm running a stock fan with clutch and a stock shroud. Is it the fan clutch? Is it air somewhere in the system (if so, how do I get it out?). I think this will work well if I can sort out the mess.
Team Owner
Joined: Aug 2006
Posts: 24,125
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From: Columbia Missouri
There is probably air building up under the T-stat right now giving you false temperature readings. Drill a small 1/8" hole in the t-stat rim to allow that air pressure to bleed through the system.
Also, next time your engine is hot and running, open the hood, and shut off the car. Watch how many times the fan turns before it stops. The fewer the better. If the fan spins more than once or twice then it's not engaging at operating temp and the clutch needs to be replaced.
Also, next time your engine is hot and running, open the hood, and shut off the car. Watch how many times the fan turns before it stops. The fewer the better. If the fan spins more than once or twice then it's not engaging at operating temp and the clutch needs to be replaced.
Race Director
Joined: Feb 2005
Posts: 16,100
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Coolant temps of just below 200 at highway speeds are ok....note that your fan clutch will release (relax) at about 55-60 mph...it will engage at lower speeds on demand if it is the thermostatic type (there is a spring on front face of clutch if you have that type of fan clutch) That spring senses temps flowing thru your radiator..and engages at about 190-200 F or so...
What thermostat rating are you using ??
Rich
What thermostat rating are you using ??
Rich
Thread Starter
Instructor
Joined: Aug 2002
Posts: 231
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From: Tucson AZ
I think it's a 185. I'll pull the thermostat this weekend and drill the hole, sounds like that could definitely be the problem. Interestingly enough, it seemed to be better today, maybe the bubble moved out? I opened the heater core up yesterday (I have a bypass valve on it in addition to the factory one) to see if I could get anything to move. I wasn't sure how to check if the fan clutch was good or not. I've been spinning fans on all sorts of cars to see if I could tell the difference (I couldn't). Everyone looked at me weird....I have the stock fan and clutch with the temp coil on the front. Your description of the car speed and fan operation seem to match up precisely with what I'm seeing. The aluminum radiator definitely runs cooler at lower speeds where I'd see the engine heat up at stop lights. It runs opposite now, cooler at slow speeds, hotter at higher speeds over 55. I also set my timing back a few degrees, it was about 12 BTDC when I checked it tonight. I backed it off to around 8. I'll check the fan tomorrow when I drive it home from work. Thanks!
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Hotter at high speeds means that air is not being forced through the radiator. You need to scoop up that air the car is driving through as that's what passes through the radiator to cool the water at higher speeds.
Is that chin spoiler in place or maybe all cracked and damaged from too many parking bumpers? It plays a large role in scooping up air.
Also, what condition are the radiator core support seals and is there insulation in that gap between the radiator and the support?
If those areas are open, the air can slide right over the radiator without ever going through it which means less cooling.
Is that chin spoiler in place or maybe all cracked and damaged from too many parking bumpers? It plays a large role in scooping up air.
Also, what condition are the radiator core support seals and is there insulation in that gap between the radiator and the support?
If those areas are open, the air can slide right over the radiator without ever going through it which means less cooling.
Last edited by Durango_Boy; Sep 7, 2007 at 08:20 AM.
Melting Slicks
Joined: May 1999
Posts: 2,897
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From: Moon Township PA
What makes you think that the thermostat is good? Try running your car without the thermostat just to see if you get the temp spike. Then take your thermostat and put it in a pot of water with a candy thermometer. Heat up the water and see what temp the stat begins to open. That is the number of the stat. So a 185 BEGINS to open at 185 degrees.
Gary
Gary
Race Director
Joined: Feb 2005
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I think it's a 185. I'll pull the thermostat this weekend and drill the hole, sounds like that could definitely be the problem. Interestingly enough, it seemed to be better today, maybe the bubble moved out? I opened the heater core up yesterday (I have a bypass valve on it in addition to the factory one) to see if I could get anything to move. I wasn't sure how to check if the fan clutch was good or not. I've been spinning fans on all sorts of cars to see if I could tell the difference (I couldn't). Everyone looked at me weird....I have the stock fan and clutch with the temp coil on the front. Your description of the car speed and fan operation seem to match up precisely with what I'm seeing. The aluminum radiator definitely runs cooler at lower speeds where I'd see the engine heat up at stop lights. It runs opposite now, cooler at slow speeds, hotter at higher speeds over 55. I also set my timing back a few degrees, it was about 12 BTDC when I checked it tonight. I backed it off to around 8. I'll check the fan tomorrow when I drive it home from work. Thanks!
The best test for your fan clutch is watching it when you shut engine off...it should stop within 1-2 turns...also,you can check it with engine off by grasping a fan blade to make sure there is no excessive play (front to rear...) 1/8" play is a good clutch...check front surface for oil/fluid leaks..
Based on your description of "slightly less than 200" at highway speeds tells me you do not have a problem...
Rich
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Thread Starter
Instructor
Joined: Aug 2002
Posts: 231
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From: Tucson AZ
I checked the fan clutch, and it stopped within one turn. I think there must be air in the system somewhere, probably in the thermostat housing. The car didn't seem to run these temps until I put the new radiator in. There is a noticable and rapid change in temp between 55+ and about 50, probably 30 degrees of difference in a matter of about 20 seconds. Maybe I'm just watching too much. The car seems to run better, and when I get it in the garage, the temp is at or just below the first hash mark which is about 15 degrees cooler than before. It definitely runs much cooler at slow speeds and while idling. I don't have good seals around the radiator, but my dam is in good shape. I'll try drilling the thermostat this weekend and see if that gets rid of the temp spike problem during the initial phases of engine warm up. The real test once I get the spike fixed will be running the a/c. If it stays about the same temp as it is now, I'll be happy. I'll let you know how this mini drama unfolds. Thanks again.
Drifting
Joined: May 2005
Posts: 1,629
Likes: 4
From: Somers CT
I'm not sure this adds to much helpful information but I have a similar reaction going on in mine. I had a stock ZZ4 with a stock radiator which I had re-cored, cooling was excellent....the car ran consistantly at 190-195 deg. even with A/C on.
Last winter I changed the heads to Brodix IK-180's and installed a mild cam. When doing the work I saw the radiator was weeping in several spots so I got irritated and bought a DeWitts. Now the temps run at 200+ all the time and rise up a lttle more from time to time for no apparent reason. It's not anything to worry about but even if the new heads do make the engine run a little hotter I was suprised to see that the added cooling efficiency of the DeWitt design would not have nulled out the temp rise. I do not have a hole drilled in my 180 deg stat and did not touch it when doing the work. I wonder what the results would have been if I had stayed with the stock radiator.
Good luck with your investigation, but I don't think the temps you're seeing are too abnomal.
Bill
Last winter I changed the heads to Brodix IK-180's and installed a mild cam. When doing the work I saw the radiator was weeping in several spots so I got irritated and bought a DeWitts. Now the temps run at 200+ all the time and rise up a lttle more from time to time for no apparent reason. It's not anything to worry about but even if the new heads do make the engine run a little hotter I was suprised to see that the added cooling efficiency of the DeWitt design would not have nulled out the temp rise. I do not have a hole drilled in my 180 deg stat and did not touch it when doing the work. I wonder what the results would have been if I had stayed with the stock radiator.
Good luck with your investigation, but I don't think the temps you're seeing are too abnomal.
Bill
Team Owner
Joined: Jul 1999
Posts: 65,492
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From: Orange Park Florida
ALLL OF YOU guys......T stats these daze can be VERY unreliable, and so even IF it was working in the first wetted install, on the second wetted install it will NOT OPEN....don't ask...many cars over the decades, and I have proven the point over and over again with thermocouples heat sunk onto the housings all over the place.....I don't trust infra red heat guns....they all over the map, depending on the color of what you are shooting at.....don't ask, I have tested them too....
When pulling the water out, either change or remove the stat entirely....I run a stat in winter, and pull it in the spring.....
sometimes I don't bother running a stat in winter, well, what passes for winter here in Florida anyway....this in the work truck....
to the fellow with a DeWitts not cooling....pull the stat and toss that thing....
When pulling the water out, either change or remove the stat entirely....I run a stat in winter, and pull it in the spring.....
sometimes I don't bother running a stat in winter, well, what passes for winter here in Florida anyway....this in the work truck....
to the fellow with a DeWitts not cooling....pull the stat and toss that thing....
Race Director
Joined: Feb 2005
Posts: 16,100
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This is a very good link explaining the C3 cooling system...the thermostat serves a very important function...there is also some good info on the fan clutch,etc...
A good thermostat to use is the Robert Shaw type that fail open...
http://www.dewitts.com/download/cooling.pdf
Rich
A good thermostat to use is the Robert Shaw type that fail open...
http://www.dewitts.com/download/cooling.pdf
Rich
Last edited by rihwoods; Sep 8, 2007 at 11:30 AM.
Thread Starter
Instructor
Joined: Aug 2002
Posts: 231
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From: Tucson AZ
Final closure on this. I drilled a 1/8" hole in the thermostat and that cured the temp spike problem. I also went to Lowes and got some water heater pipe insulation and filled in all the gaps around the radiator to ensure all the air flowed through it. The result? Today I was stuck in 90+degree heat sitting still in traffic for about 20-30 minutes and the temp never got past the first line. When I got to speed (we'll say 55+ because I never exceed the legal limit) on an open stretch of highway, it barely went over the first line. Bottom line, it looks like I've got it licked finally. Thanks for all the advice.
Instructor
Joined: Apr 2006
Posts: 114
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From: Spring Texas
Final closure on this. I drilled a 1/8" hole in the thermostat and that cured the temp spike problem. I also went to Lowes and got some water heater pipe insulation and filled in all the gaps around the radiator to ensure all the air flowed through it. The result? Today I was stuck in 90+degree heat sitting still in traffic for about 20-30 minutes and the temp never got past the first line. When I got to speed (we'll say 55+ because I never exceed the legal limit) on an open stretch of highway, it barely went over the first line. Bottom line, it looks like I've got it licked finally. Thanks for all the advice.
I did as TXShark did above but with little help. But I'm not running a stock 350 anymore. I have a 500 horse SB400 .030 over with Dart heads. I had the radiator vatted when I replaced the engine. With ambient temps near 100 degrees this summer down here in Houston, TX, I can't drive it.
I'm thinking about a 4 core or aluminum radiator. Also maybe adding a fan in the radiator shroud. I only want to do this once.
What aftermarket radiator is the best for the buck? What other suggestions you guys may give me?
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
I did as TXShark did above but with little help. But I'm not running a stock 350 anymore. I have a 500 horse SB400 .030 over with Dart heads. I had the radiator vatted when I replaced the engine. With ambient temps near 100 degrees this summer down here in Houston, TX, I can't drive it.
I'm thinking about a 4 core or aluminum radiator. Also maybe adding a fan in the radiator shroud. I only want to do this once.
What aftermarket radiator is the best for the buck? What other suggestions you guys may give me?
I'm thinking about a 4 core or aluminum radiator. Also maybe adding a fan in the radiator shroud. I only want to do this once.
What aftermarket radiator is the best for the buck? What other suggestions you guys may give me?
You are just straight west of me....and with that engine pushing about 25% more than I am....I suggest you use DeWitts' suggestions, and a Dual Spal setup....it's expensive, but it.....
WORKS
Thread Starter
Instructor
Joined: Aug 2002
Posts: 231
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From: Tucson AZ
The Dewitts aluminum radiator dropped right in. It even had the correct dent in the lower radiator outlet and fit like the original without any mods at all. Definitely worth the little bit extra they cost than a be cool or other type. I found they were cheaper directly from the company rather than going through Corvette Central or the other catalogs. I'm running a stock shroud and fan with a clutch. I will say that at one point during the install, I thought seriously about putting in the dual fan set up. My wife came out to help me (and who must have seen the cost of the dual fans...) showed me where the shroud was hitting the upper transmission cooler line. I pulled it off and the shroud dropped right in. My little stroker motor seems to like the set up I have, so I'm saving my pennies for the Steeroids rack and pinion set up. Good luck and thanks again for the help and support.