Overheating on Hwy
Thread Starter
Burning Brakes
Joined: Apr 2007
Posts: 1,028
Likes: 1
From: SOUTH ELGIN IL
Overheating on Hwy
Hi all,
I've got some problems with this car, but my most recent one has to do with cooling. I'm running the stock radiator, stock mechanical fan and a pretty old looking water pump that came on the ZZ4 when I bought the car. Car runs at about 210F but i had it on the highway yesterday and it shot up to about 240 at 65-70mph and then came right back down (in seconds) when I slowed down to under 45mph. Oh, I replaced the seals around the radiator last year as well.
At hwy speeds i would expect enough air flow to be forced through the radiator to keep the car cool and at low speed it should be living off the fan, right?
Does this sound like my water pump is bad? Time for a radiator w/ Spal fans?
I've got some problems with this car, but my most recent one has to do with cooling. I'm running the stock radiator, stock mechanical fan and a pretty old looking water pump that came on the ZZ4 when I bought the car. Car runs at about 210F but i had it on the highway yesterday and it shot up to about 240 at 65-70mph and then came right back down (in seconds) when I slowed down to under 45mph. Oh, I replaced the seals around the radiator last year as well.
At hwy speeds i would expect enough air flow to be forced through the radiator to keep the car cool and at low speed it should be living off the fan, right?
Does this sound like my water pump is bad? Time for a radiator w/ Spal fans?
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Almost certain your lower rad hose is not properly supported with a spring in the middle, allowing it to collapse under suction into the pump feed/return.....make damn sure it's not happening, rev the engine pretty good and watch that hose....
another thing, make damn sure your t-stat is opening...I would get a new one, and drill 2-3 1/8 inch holes around the perimeter, that allows for more flow than normal, but still will keep engine at 180f or 195f if you have to....
another thing, make damn sure your t-stat is opening...I would get a new one, and drill 2-3 1/8 inch holes around the perimeter, that allows for more flow than normal, but still will keep engine at 180f or 195f if you have to....
Drifting
Joined: Feb 2005
Posts: 1,879
Likes: 38
From: Los Gatos CA
Yes, at freeway speeds air flow across radiator should not be a problem, unless something is blocking it. Freeway speeds are a high load condition that require more cooling. It sounds like your problem is radiator effiiciency. How old is your radiator? I believe it needs to be rotted out or recored. But the thermostat advice is good. In one of my old trucks, it was running hot and I swore it must be the radiator. An old mechanic advised me to try the easy thing first and replace the stat. $3 and 10 minutes later the problem was solved.
Last edited by Jeff_Keryk; Jul 3, 2009 at 11:15 AM.
Thread Starter
Burning Brakes
Joined: Apr 2007
Posts: 1,028
Likes: 1
From: SOUTH ELGIN IL
It's the stock radiator, and from the looks of it I bet it's never even been flushed, much less cored.
Ill take out the t-stat and switch out the hose first to see if there's a difference.
Ill take out the t-stat and switch out the hose first to see if there's a difference.
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
after that, maybe wonder if you can see between your rad and the a/c condensor......plastic bag in there blocking flow....
could be something stupid, but I bet you maybe on the rad at this point, from your comment....
Thread Starter
Burning Brakes
Joined: Apr 2007
Posts: 1,028
Likes: 1
From: SOUTH ELGIN IL
I went and bought a new lower radiator hose and the guy at Autozone told me since it didn't come with a spring it shouldn't need one... does this sound right to everyone else?
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
If the new lower hose is corrugated, it will probably stay open under suction from the water pump. If it's not, your guess is as good as mine. If you decide to clean up the inside of your radiator, use radiator cleaner....not radiator flush. The flush stuff will get loose gunk out; but the cleaner will also remove any built-up deposits on the inside of the cooling fins. And that's were the efficiency of the radiator is lost. It's more trouble than flushing, but it will make a considerable difference in the performace of a 'cruddy' radiator.
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Team Owner
Joined: Jan 2007
Posts: 53,648
Likes: 878
From: Southern Cal Ca
St. Jude Donor '22
Something about the rubber is better and it won't collapse.
Thicker wall maybe.
I have been recycling my spring with the so called better hoses.
Racer
Joined: Mar 2008
Posts: 315
Likes: 0
From: KY
I had the same problem with the stock rad. and my zz4 so I replaced it with a Dewitts sp 031
http://www.dewitts.com/pages/categor...s.asp?catID=15
http://www.dewitts.com/pages/categor...s.asp?catID=15
Thread Starter
Burning Brakes
Joined: Apr 2007
Posts: 1,028
Likes: 1
From: SOUTH ELGIN IL
Yeah, I've been looking at the DeWitts SP034 for my vehicle. However, I think I'll start with the hoses, cleaner, and borrow an electric puller fan from a friend and see what happens. I'll also check the lower air damn. After that I'll bump up to the DeWitts, maybe next time Tom has a sale or group buy option.
Sure would be nice to run at 180F...
Sure would be nice to run at 180F...
Pro
Joined: Jun 2005
Posts: 725
Likes: 1
From: FL.
time to deal with dewitts, Overheating due to old Radiator, hoses , gunk, Is one of the worse nighmares with owning an oldie but a goodie. I say Bite the Bullitt unless You you cant see through the cost right Now. In that case, sure, core and Flush may get you along at decent temps
Le Mans Master
Joined: Oct 2005
Posts: 6,247
Likes: 471
From: Glen Allen, VA
How exactly would you use the radiator cleaner. My car has always had a similar problem, but not as bad. On a very hot day, mine will creep up towards 220 on the highway and only on the highway. It will idle all day long in 100 degree heat and not creep up, and as said above, as soon as I come off the intersate, the temp comes down. I've drained, and filled the radiator with radiator flush I believe it was, not cleaner. I refilled, ran the car till the t-stat opened, then drained it, refilled and repeated the process until I was getting clear water out. Now the coolant water mix is just as green as it should be. Any other suggesitons?
Advanced
Joined: Dec 2006
Posts: 50
Likes: 1
From: So. Cal. CA
+ 1 on the airdam/spoiler.
How long does it take for the temp to get that high? For me, it would increase over time, but wouldn't make it up that high until 30-45 minutes of freeway driving. After the spoiler, freeway speed temps stay the same even over a couple hour cruise.
Mike
How long does it take for the temp to get that high? For me, it would increase over time, but wouldn't make it up that high until 30-45 minutes of freeway driving. After the spoiler, freeway speed temps stay the same even over a couple hour cruise.
Mike
Race Director
Joined: May 2007
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From: Out of Site...Out of Mind. Corvette: anything else is just transportation.
St. Jude Donor '09 thru '20
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
If your radiator doesn't leak nor have a lot of fin damage, what have you got to lose trying to clean it out? $5 for the cleaner and a little of your time? Just buy a bottle of cleaner at your local car parts store, follow directions on the bottle. It will take a couple of days for it to work. Then, if no leaks show up, put in fresh 50/50 mix of water/glycol and try it out. I'd bet you're "good to go". 
Thread Starter
Burning Brakes
Joined: Apr 2007
Posts: 1,028
Likes: 1
From: SOUTH ELGIN IL
switched out the t-stat for a 160 from a 180 and driled 3 holes in it, now car idles at about 160, maybe 170- much lower than the previous 210. Drive for about an hour and under 200 in stop and go traffic but still about 220 on the highway. Lower radiator hose is not collapsed and upper is also fine.
I think I'll flush and clean next but since it stays cool at idle and mid level loading I'm thinking that won't help much.
I think I'll flush and clean next but since it stays cool at idle and mid level loading I'm thinking that won't help much.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
If you take the radiator to a shop they will remove one of the end tanks and run a flat "rod" through each tube and clean them out, hence the term "rod out".
