1977 Overheating
Thread Starter
Racer
Joined: Jun 2009
Posts: 276
Likes: 2
From: Parkesburg PA
1977 Overheating
Hey everyone. Last weekend my car started to overheat. I just put in an aluminum radiator from Zip (Tom Dewitt said it was a good piece and I should be pleased). I have a new upper hose and a 2 year old lower hose. I have the "air dam" on the front under the nose and 2 flex-a-lite electric fans that pull air through the radiator. I have the foam air seal on the top of the rad support against the hood. After the new radiator install the car still runs at about 230-245. Before I started having these issues the car would run at about 210-215. Nothing was changed before the overheating started. When cruising down the highway I notice the biggest temperature increase. Once off the highway the RPMs drop and the temp will go down some, but still seems a little high. Any ideas why something like this would suddenly start? The intake is about a year old and the radiator I replaced was only about 2 years old. Thanks in advance!
Melting Slicks
Joined: Mar 2009
Posts: 3,126
Likes: 15
What I would look at. No offence intended. Are you sure the fans are turning the correct direction. DC motors are very easy to make run backwards. Second what temp. thermostat are you using? Overheating at highway speeds normally means a restricted flow of coolant or air through the radiator. Is it possible that the lower radiator hose is collapsing at highway speeds? I drove my '77 today in 93 degree ambient with the Dewitt's radiator and a 180 degree Mr. Gasket thermostat with the A/C on and it never got above 180 degrees. Good luck with it. mike...
Thread Starter
Racer
Joined: Jun 2009
Posts: 276
Likes: 2
From: Parkesburg PA
What I would look at. No offence intended. Are you sure the fans are turning the correct direction. DC motors are very easy to make run backwards. Second what temp. thermostat are you using? Overheating at highway speeds normally means a restricted flow of coolant or air through the radiator. Is it possible that the lower radiator hose is collapsing at highway speeds? I drove my '77 today in 93 degree ambient with the Dewitt's radiator and a 180 degree Mr. Gasket thermostat with the A/C on and it never got above 180 degrees. Good luck with it. mike...
Melting Slicks
Joined: Mar 2009
Posts: 3,126
Likes: 15
I have never seen it happen but the old tale is that the lower hose can collapse if you do not have the coil spring inside. Hose would need to be pretty soft. Let's see what the real experts say about your particular problem. mike...
Thread Starter
Racer
Joined: Jun 2009
Posts: 276
Likes: 2
From: Parkesburg PA
hmmm...i have no spring in the hose but perhaps in the two years its been there its softened up enough? i wonder if someone local has one in stock.
Thread Starter
Racer
Joined: Jun 2009
Posts: 276
Likes: 2
From: Parkesburg PA
i bled the air by opening the highest hose point on the engine and saw coolant coming out, no air. timing is correct and cap is on right. no water in oil or coolant loss. i have opened cap and run engine to temp also and checked coolant levels several times.
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Drifting
Joined: Jun 2005
Posts: 1,523
Likes: 1
From: grand prairie texas
What ratio mix of antifreeze are you useing? Too much antifreeze and not enough water will run higher than normal temps. I use 60% water 40% antifreeze mixture. My 77 with a mildly built 350 and a stock turbo 350 transmission with 308 gears will run all day in our Texas heat with the A/C on at 200 degrees. I do have the Dewitts radiator with the twin fans. If Tom said what you bought should be a suitable replacement you should no go over the 200 degrees. I am running I think a 195 thermostat.
Thread Starter
Racer
Joined: Jun 2009
Posts: 276
Likes: 2
From: Parkesburg PA
What ratio mix of antifreeze are you useing? Too much antifreeze and not enough water will run higher than normal temps. I use 60% water 40% antifreeze mixture. My 77 with a mildly built 350 and a stock turbo 350 transmission with 308 gears will run all day in our Texas heat with the A/C on at 200 degrees. I do have the Dewitts radiator with the twin fans. If Tom said what you bought should be a suitable replacement you should no go over the 200 degrees. I am running I think a 195 thermostat.
Thread Starter
Racer
Joined: Jun 2009
Posts: 276
Likes: 2
From: Parkesburg PA
Yes, vacuum advance is hooked up and i checked it earlier to ensure it was working. I did try to both retard and advance the timing, but no luck. I'm going to pickup a hose w/ a spring in it this week. I also got new plugs and wires just for the heck of it.
Drifting
Joined: Jun 2005
Posts: 1,523
Likes: 1
From: grand prairie texas
Are you sure both of your fans are running? What CFM are your fans? Sounds like you have thought or tried pretty much everything. Can you confirm the car is actually overheating and verify with a good temp device?
Former Vendor
Joined: Jan 2000
Posts: 5,593
Likes: 631
From: Brighton
I'd question the gauge reading first. Your gauge or the temp sending unit may be defective and telling you a lie. Many times people will chase a problem they don't really have and only find this out after spending lots of time and money. Check that reading with an IR gun before doing anything else. The spring in the lower hose is a good idea and while your are there, check for plugs and rags and things. Sometimes people with stuff something into the water pump and/or hose to prevent a flood and forget to pull it out. I've gotten radiators returned that were "defective" and they still had the rag stuffed in there
Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
We are all chasing the thought that it's not cooling enough. Could it be your engine is producing more heat than normal? Have you noticed any change in your oil pressure? Any abnormal sounds? How many miles on it?
With the aluminum radiator running down the highway it should be cooling. Get it to a fair size hill and start down it put it in neutral and coast some. See if the temp drops then.
With the aluminum radiator running down the highway it should be cooling. Get it to a fair size hill and start down it put it in neutral and coast some. See if the temp drops then.
Thread Starter
Racer
Joined: Jun 2009
Posts: 276
Likes: 2
From: Parkesburg PA
Sorry for my delay here. I think the gauge might just be the issue here. Where should I check the temperature with the IR gun? I'm getting drastically different readings when pointing it at different locations under the hood. Near the temp sensor and also at the thermostat housing seams low to me. That's probably because the metal is dissipating some of the heat. Where will I get the most accurate reading? Thanks!
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
Easiest places to check is the manifold at the base of the tstat housing and then on the radiator tank just after the top hose port.
They read metal more accurately and hold it an inch away from the metal. You are checking to see if the tstat opened properly. Both should be the same. Lots of bad ones these days. The cheaper guns have a cone shaped area that reads very wide very quickly, so the closer the better.
Lower rad outled or water pump inlet should be approx 30° less than the rad inlet @ approx 1500 rpm.
Best is to fill the overflow tank all the way and let it puke out the extra on several heat cool cycles. This is after you think the rad is completely full.
They read metal more accurately and hold it an inch away from the metal. You are checking to see if the tstat opened properly. Both should be the same. Lots of bad ones these days. The cheaper guns have a cone shaped area that reads very wide very quickly, so the closer the better.
Lower rad outled or water pump inlet should be approx 30° less than the rad inlet @ approx 1500 rpm.
Best is to fill the overflow tank all the way and let it puke out the extra on several heat cool cycles. This is after you think the rad is completely full.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
I bought me one of these to confirm readings on the gauge in the cabin
http://www.ebay.com/itm/MR-GASKET-TH...item5647c0ac51
The radiator regularly reads about 20 degrees cooler than the cabin gauge, which makes sense due to it's location vs the reading in the cylinder head that the cabin gauge gives. It at least can verify or deny cabin gauge readings on the road. The real restriction ultimately is boiling the water out of the radiator after all.
http://www.ebay.com/itm/MR-GASKET-TH...item5647c0ac51
The radiator regularly reads about 20 degrees cooler than the cabin gauge, which makes sense due to it's location vs the reading in the cylinder head that the cabin gauge gives. It at least can verify or deny cabin gauge readings on the road. The real restriction ultimately is boiling the water out of the radiator after all.