I took the Vette out today and it did something it has never done. This should be a simple diagnosis for some senior members, help out a self admitted "bloody knuckler" will ya? :D

I'm tooling around in town doing 50 MPH between lights. It's 75 degrees out, I'm not pushing the car. Temp is looking good, hovering around 160. I get on the freeway and WHAMMO, it jumps almost to the danger zone within 1/2 a mile? I was doing about 70 @ 3200 RPM's, I get off the freeway and it slowly cools back down to about 200 when I get back on city streets?

Let me preface with how the system is set up: It has one of those goofy flex fans on it. I know the radiator is not "correct" because I flushed the system a couple of weeks ago and the correct lower hose (which I replaced) did not fit. When I refilled it I went 60/40 water/coolant and a bottle of Water Wetter for good measure. There's 1" of "gaposis" on the fan shroud to the radiator so it is not pulling heat off as efficiently as it could. Water pump sounds okay, not leaking. Although not a perfect "desert cooling set up", I don't see any of this as the cause of the problem. Any thoughts on this?

My logic says if it got hotter at speed then it's probably a cooling system issue, not an air flow issue? I'm going to replace that goofy fan and possibly put a fan clutch on but again, I don't think this will address the issue. What do you guys think, radiator bad? Thermostat sticking? I'm sure someone is out there going "hey, that happened to me!"

Thanks,

Bob

 

I'd think radiator isn't up to par, but seals and air dam are a must. Read Rich's75 post on his cooling solution http://forums.corvetteforum.com/zerothread?id=393445
I've heard clutched fans like that kick in. but mine never has.
I've got new; Radiator,seals, Stewart pump,hi flow thermostat and fanclutch. I've confirmed the gauge temp, it'll stay at 180 all day from idle to about 3000K(60 mph) after that it climbs to 205-210 and never goes higher. This has always bugged me :rolleyes: . But now I just accept it.

Scott


[Modified by Scott78, 6:38 PM 9/21/2002]

 

I would say thermostat since it happened so quickly. Get one of these; a superior product. My temp gauge is bang on 195F from 90F ambient heat to 65F. City to highway. Rarely varies. A good investment for about $8.00.

 

Thanks for the reply Scott. I'm thinking radiator as well. I read Rich75's thread (twice) and I didn't get it? Sounds like he's saying that due to the fan clutch failure and he ran cooler; then when he replaced it, it ran hotter again? Maybe I need to go read it a third time :smash:

A.D.D. boy signing off for now........ :lol:

Bob

 

No you read it right the clutch failed in the "locked" position and cooled the car off. I've never seen it published any where but I'd have to bet the stock vette fan clutch doesn't kick in till at least 220 or higher.

Scott

 

The 'chin' air dam is absolutely critical to high speed cooling. Also the radiator to support and support to hood seals. Without these, the car just does not direct enough air flow through the radiator.

As a side note, I suffered the same problems with my '75. Everything that I did helped some, including new radiator, hoses, thermostat, seals, etc. Like I said, everything helped but nothing completely cured the problem.

A couple of months ago, I was screwing around with the timing and discovered that my vacuum advance was not working. So, off to the FLAPS. Nine bucks and change later, I installed the new vacuum advance can. The temperature is now solid as a rock.

This is not to say that you don't have issues with the cooling system. But, it may not be the complete answer . . .

 

Heh Bob J,
You have a lot of issues there that need attention. 1.. Incorecct Rad. 2.. the Fan 3... The Shroud..
There has been a ton of post's on the C1- C2 forum about Vette Cooling and Rad's and shrouds and fans. My suggestion to you would be to jump to the C1-C2 Forum and look up the cooling system Posts.

There was a lot of back and forth on this subject and some hot debait.

Also Tom DeWitt of Dewitt Rad's also monitors this forum and has helped me as other's with cooling problems. Or you could go to his web site and ask him directly via email for some help.
The guy Knows his stuff.............
:cheers:


[Modified by Viet Nam Vett, 9:47 PM 9/21/2002]

 

Bob,
Do you have the front spoiler on the car?
Do you have the proper radiator/shroud air seals?
Do you have a front license plate?

Those can all lead to inefficient airflow at speed and can be factors in yoru problem. Coolant flow being insufficient is another, but the biggest factor in my mind is the radiator not being able to reject that amount of heat.

I took my engine driven fan off my car a week ago and I run nice and cool at speeds. I heat up of course when I'm stopped (need to remember to flip on the electric fan!).

You recently flushed the system, too? Hmmmm...odd. We'll figure it out.

 

Could the lower hose be collapsing (lack of spring) at the increased RPM/suction of highway speeds?? I know you said the lwr. hose was not a correct fit.

Just a thought.


[Modified by shoptek, 12:05 AM 9/22/2002]

 

First, if you replace the thermostat, make sure you test it first. Use a yeast thermometer, and heat some water on the stove. Watch at what temperature the thermostat opens and closes.

Second, make sure you purge all the air from your system. The best way I know how, is to securely raise the front end of the car. Lift it high enough so that the radiator cap is the highest part of the car. Then, open the cap (with the engine cool) and let your engine idle for fifteen minutes or so. Occasionally, goose it, and let it rev at 2000. You don't need to do this too long. Just make sure you have good flow. Also, squeeze your upper radiator hose a few times.

This, along with a new water pump, solved my cooling issues. I hope it helps you.

:cheers:

 

my cooing system bit the dust last winter. i had the rad recored with extra fins. had the original water pump rebuilt. new hoses and thermostat. my car says at 190-200. even on hot days stuck in traffic.

 

I would bet this is an air flow issue. The way this thing is set up it sucks the air through the radiator based on high/low pressure created by the duct work (the air moves from high pressure to low pressure). With these gaps, etc., the air is being diverted because the low pressure is not in the right place causing the high pressure air to go there instead of through the radiator as it should.

Bob

 

Thanks for all the responses. The chin air dam is in place. "collapsed lower hose", VERY interesting!!!!

Looks like I've got some diagnostic work to do. Probably start by replacing the T-Stat and sealing the shroud.

Thanks again for all the input...........

Bob