Is she overheating????

[AUSSIEVETTEMAN]

OK, well I have done just about everything to reduce the temperatures on my old girl, but I am not winning.

We have:
Replaced the original 2" radiator for a big block/ HD radiator which has 4 rows and is 2 5/8" thick. This has been pressured tested and is OK.
Replaced the thermostat from a 195 degree to a 160 degree and this works fine.
Replaced the top and bottom radiator hoses with Coolflex hoses as these have a lifetime warranty and will not split or suck in while highway driving.
Replaced all of the seals around the radiator and shroud.
Replaced the 6 blade manual fan that was on the water pump with a 7 blade clutch fan, in hope that this will draw more air through the A/C cooler and radiator.
We have two new air dam extentions, thanks to Corvette Central, to put on the bottom of a new air dam they also supplied. (Ours was broken and the last owner bogged it up with body filler, but it has broken now). These have not yet been put on.
We have had the system pressure tested and this found a very small leak in the head gasket, but we replaced these when the new carb went on.

OK, here are the temps:
First start for the day will see the temp guage go up to around 180 before it dives back down to 160 indicating the thermostat is opening.
Normal driving and driving on the highway show temps of around 170 to 190 depending on what driving style!!
Driving in traffic is different though, she starts to pull temps of around 200 to 220 especially when in 'drive thru' resturants. If you put the A/C on, the auxillary fan will cool her slightly, but only a couple of degrees. As soon as you start driving again from being stuck in traffic, the temps go back down.

I think the air flow needs a bit of a 'touch up' and am thinking of a thermo fan that will suck a golf ball through a garden hose, well that type of power anyway.

What do you guys reckon or can you suggest anything I have missed???

Cheers

Tony

 

[cdr63corv]

I was having some of the same problems myself. Not much I can add except did you put the 160 thermostat in at the same time as the radiator? I had put a 160 in last year and found it actually heated up more, I think the 160 opens to much not allowing the radiator enough time to cool the coolant down it just flows through to fast, just my opinion. I had the heator core plugged off on mine due to leakage and just replaced it wont know if this worked till spring or not. Good luck............

 

[DDLS3]

Tony

I didn't happen to see that you replaced the water pump. It's possible that there isn't much of an impeller left or there may be a blockage. A higher flow pump could help you as well, they are available from Jegs or Summit pretty reasonable. Second, are you certain that the gauge and or sensor are working properly? The 160 degree t-stat isn't doing much for you, whether the t-stat is wide open at 160 or at 190 open is open. Your engine will like the hotter temp. My 81 will rise to 200-205 in traffic or on a real hot day with the a/c on. This has never been much of a problem. If by chance your head gasket leak returned, that alone will account for some extra heat. Might not hurt to repeat the test to make certain.

 

[Bob Chadwick]

Tony,

I don't see where you mention this so what are your external temps? This is exactly what my car does on a 95 degree day in Atlanta. On a 75 degree day I would be concerned.

The gauges are not always accurate on these cars. You might want to purchase one of those thermal units, infrared I think, and confirm the temps that you are getting.

The 160 degree thermostat is too cold for your car. You want 180. Low temps cause excessive wear due to the oil not getting hot enough, etc.

Bob

 

[78SilvAnniv]

Sounds like you did the same things we did when we had our run-hot problem.
Replaced clutch fan yearly, water pump, radiator, belts/hoses, t-stat even a new crate engine was installed and I still had the same problem.

I think I recall that timing can affect operating temperatures...perhaps that is an area you can check?

My run-hot problems occured every California/Washington summer since we owned the 78. (since 1990) Everytime the summer temps climbed we had to drive no faster than 60mph and avoid stop/go traffic. AC?...try shooting temp up to 240*!

When we moved to Georgia I was frustrated with the run-hot problem and wanted to be able to use the AC. I removed the clutch fan from the water pump and installed a flex fan. Loads of air is sucked through the AC and water radiators and forced through the engine compartment.
I have not exceeded 195* while driving sustaned 75mph, 2nd gear @ 2500-3500rpms taking uphill mountain curves, AC at hwy or town speeds and idle. My temp usually hangs out at 180* with normal driving.

It has been stated before that changing the GM cooling design will not fix every cooling problem, but installing the flex fan fixed mine after 12 summers of run-hot problems.
Heidi

 

[GerryLP]

Tony,

It appears that you have been checking the cooling system extensively, and I would be inclined to think that the problem could be somewhere else.

I suspect that you're not getting a "check engine" light, so have you checked the air cleaner housing snorkle damper doors to see if they're opening after engine warm-up? If not, it could be vaccume leak on the hoses, a bad temp sensor (the one attached to the housing near carburator air horn), or bad door actuator(s).

You could also have a leaking (internally) EGR valve. Switch vaccume source for EGR valve with another source. If engine rpm does not drop, then its leaking.

The oxygen sensor should trigger a "check engine" light code, but this doesn't happen always. The sensor could be giving a rich signal, and the ECM in turn orders the Mixture Control (MC) solenoid to lean-out. Lean mixtures drive temperatures up.

Whatever it is, it appears to be subtle, since it is not causing the engine to run hot all the times, or the cooling system can overcome it during most of the driving conditions.

 

[AUSSIEVETTEMAN]

Could be a good point.

I was having some of the same problems myself. Not much I can add except did you put the 160 thermostat in at the same time as the radiator? I had put a 160 in last year and found it actually heated up more, I think the 160 opens to much not allowing the radiator enough time to cool the coolant down it just flows through to fast, just my opinion.

Actually I have a Corvette Mechanic here and he said the same thing. I may try another thermostat.

Cheers
Tony

 

[AUSSIEVETTEMAN]

Thanks Dale

I didn't happen to see that you replaced the water pump. It's possible that there isn't much of an impeller left or there may be a blockage. A higher flow pump could help you as well, they are available from Jegs or Summit pretty reasonable. Second, are you certain that the gauge and or sensor are working properly? The 160 degree t-stat isn't doing much for you, whether the t-stat is wide open at 160 or at 190 open is open. Your engine will like the hotter temp. My 81 will rise to 200-205 in traffic or on a real hot day with the a/c on. This has never been much of a problem. If by chance your head gasket leak returned, that alone will account for some extra heat. Might not hurt to repeat the test to make certain.

I thought about redoing the test to see if the leak was still there. Those other gaskets were original, so the engine has never been rebuilt. It had original GM gaskets on it. Good point, I will repeat the test just to make sure.
The water pump was replaced by a previous owner a couple of years back. It seems to be working good and when I put the clutch fan on, it wasn't leaking or had no play in the shaft. No bad noises either.
As for the guage and sender unit, that was the next step before the thermo fan/s.
The temperature that day was 38 degrees, a hot one for us for summer. Normally around 28 to 33 on a summer day. I'll see how she goes today.

Cheers
Tony

 

[AUSSIEVETTEMAN]

Well you are right.

Tony,

I don't see where you mention this so what are your external temps? This is exactly what my car does on a 95 degree day in Atlanta. On a 75 degree day I would be concerned.

The gauges are not always accurate on these cars. You might want to purchase one of those thermal units, infrared I think, and confirm the temps that you are getting.

The 160 degree thermostat is too cold for your car. You want 180. Low temps cause excessive wear due to the oil not getting hot enough, etc.

Bob

Well Bob, the temperature on that day was bloody hot. It was 35 degrees celcius (around 95 degrees). She was working pretty hard to stay cool.
Those guages may be reading wrong, I will replace the sender unit first.

Cheers

Tony

 

[Bob Chadwick]

Tony,

People will disagree, but I'd be proud of the old cooling system. That temperature range is not bad for stop and go traffic on a 95 degree day. Low engine rpm's on a hot day are the toughest time for these old cars with their mechanical fans. Now if it was running 220 while moving, I would be more concerned.

I would change the thermostat back to 180 or 185, I can't remember which it is. The thermstat only sets a bottom for the temperature and absent a malfunction, does not affect the high end.

Bob

 

[AUSSIEVETTEMAN]

Sherry

Sherry,

I hope you weren't being rude!!!

Cheers

Tony

 

[AUSSIEVETTEMAN]

That sounds like another solution.

...I removed the clutch fan from the water pump and installed a flex fan. Loads of air is sucked through the AC and water radiators and forced through the engine compartment.
I have not exceeded 195* while driving sustaned 75mph, 2nd gear @ 2500-3500rpms taking uphill mountain curves, AC at hwy or town speeds and idle. My temp usually hangs out at 180* with normal driving.....Heidi

Heidi,
I was talking to an old KIWI (New Zealand) mate of mine today as he has two classic Mustangs, a fastback and a convertible. He says his temps never exceed 180 and he has also installed flex fans on both cars. He said I would have a bit of trouble trying to cool the old girl down to a level in which I was comfortable with, but it could be done, no worries! When I get her back, she was taken down to the body shop for some warranty repairs, I will install the new air dam and the air dam extensions. I think that will help while driving, but not in traffic with no airflow.

Thanks for your input, I will look around for a flex fan here in Oz.

Cheers

Tony

 

[AUSSIEVETTEMAN]

Thanks Gerry

Tony,

It appears that you have been checking the cooling system extensively, and I would be inclined to think that the problem could be somewhere else.

Thanks Gerry, my computer is not hooked up. Previous owners have diconnected the computer, changed to a Mallory ignition system and Blaster 3 coil and done some other nasty things to her, which I have to just shake my head at.
The computer is still there, but I don't think anyone is home. The carb is slightly different, I have an Edelbrock QJet, which is the same in specs except for being computer controlled and even has the same look, just with an Edelbrock badge.

Thanks

Tony

 

[AUSSIEVETTEMAN]

Tony,
People will disagree, but I'd be proud of the old cooling system. That temperature range is not bad for stop and go traffic on a 95 degree day. Low engine rpm's on a hot day are the toughest time for these old cars with their mechanical fans. Now if it was running 220 while moving, I would be more concerned.
I would change the thermostat back to 180 or 185, I can't remember which it is. The thermstat only sets a bottom for the temperature and absent a malfunction, does not affect the high end.
Bob

Bob,
Yeah, I am pretty happy so far with what we have done, but I would like to reduce these temps a little more, well the higher ones that is. I would like to leave a buffer in temperature, just in case the system is not working correctly by not being pressurised or with no coolant. These days do happen, not everyone has coolant to add when you are out in the middle of nowhere and sometimes you can only add water. It would be a shame if the system was relying on the coolant and pressurisation to not boil. I think that high temps would be high temps even without coolant. 220 only leaves 30 degrees until bad things start to happen, well in my opinion anyway. I would hate to see my baby go down that way.
That day and yesterday was very hot for us, the hotest since 1930 I think.

I will try the other thermostat idea and see how I go.

Thanks for your feedback,

Cheers

Tony

 

[Bob Chadwick]

Have you considered changing your settngs on the aux fan so that it comes on at a lower temp than the 238 that it is currently set for. I don't have this fan so I haven't looked into it but recall that the vendors have something that can help you in this regard.

 

[billyvette]

flex fan question

those who have installed flex fans.. is the fan clutch retained with the flex fan or does it work alone, like an older stock fan without a clutch?

 

[78SilvAnniv]

The entire clutch fan goes buh-bye.

The flex fan is installed directly to the water pump. You will need two aluminum spacers. (so the fan is the proper distance to/from the radiator and within the shroud).

You will need to specify spacers for a Corvette. I believe the reason you need Corvette specific spacers is because of the tilt of the radiator and the distance from the block to the shroud.



The flex fan opperates all the time according to engine rpm speed. At higher speeds the fan blades flatten out and become less effective, but the need for a fan is at lower rpm speeds. Hwy speeds keep enough air moving through the system.

I had problems driving in summer temps above 60mph before I installed the flex fan. After the install I can drive as fast as I want, as long as I want in summer temps and not see the temp go above 195*.



After installation you will notice greatly increased 'wind' sounds from the flex fan. I don't find the sound annoying at all, in fact I find it comforting to know so much air is being moved through there. Standing next to the fenders you will be able to feel the moving air when the car is at idle. After a short while you will become accustomed to the sound of the rushing air. (It is not an overly loud sound like gear drive.)
Heidi

 

[billyvette]

hey there vette girl!!!

Thanks for the response, been a while since I talked directly to you. I have a chambered exhaust and ceramic headers coming in for my car and I am finally going inside the dash to replace my heater core so I can drive year round. First full week of March is spring break, so I hope to get some of this done that week.

hope your still enjoying your vette.

where did you obtain your flex fan?

 

[AUSSIEVETTEMAN]

Auxillary Fan

Have you considered changing your settngs on the aux fan so that it comes on at a lower temp than the 238 that it is currently set for. I don't have this fan so I haven't looked into it but recall that the vendors have something that can help you in this regard.

Yeah Bob, I had a thoughty about that the other night. I know Corvette Central has a sender unit that turns the fan on at a lower temp. This maybe an option as I will have to see what the previous owners have done with the electrical work first. This fan operates with the A/C. I was trying to see if the wiring diagrams showed this or not the other night when I had the manual out.
I am pretty sure that the auxillary fan is just for cooling.

Cheers

Tony

 

[AUSSIEVETTEMAN]

Pics

The entire clutch fan goes buh-bye.
The flex fan is installed directly to the water pump. You will need two aluminum spacers. (so the fan is the proper distance to/from the radiator and within the shroud).
You will need to specify spacers for a Corvette. I believe the reason you need Corvette specific spacers is because of the tilt of the radiator and the distance from the block to the shroud.

Heidi, Do you have a pic you could post or send us?

Thanks

Tony