geoology

A little update. I put the thermostat in the car. the car will idle for ever and never go above 200 on the gauge. I start raising the rpm for long period of time the temp slowly increases but never comes down if I let it idle. If i drive the car around town never getting above about 40 the temp will rise to the 220-230 level and stay pretty constent there. The faster I drive bringing rpm and holding like on the hwy the temp will get in the 240 range and stay there until I shut the car off and let it sit a bit. Also had an older guy say try and losen the radiator cap just put it on and only twist to the first stop to seal but not tighten all the way to make it not hold as much pressure and it seemed to help it a bit.
what would cause this to be the case. I have 2 electric fans a 16 inch and a 14 inch as 2 16 inch fans would not fit. per there documentation on the box it's about 2000 cfm which is what the fan manufacture recommends. They are fans from the big parts store.

Not sure what to do next. Getting back to the manifolds I dont think they are a direct blame I just didnt know why the under hood temps were getting so hot. To the point you cant touch anything under the hood with out it burning.

thanks
geo

chevymans 77

Would be interested to know what the engine oil temps are, usually they are 10 to 20* above the coolant temps so if your coolant is at 240 then your engine oil may be 250 or higher.

If possible do a temp drop test on the radiator, check the inlet and outlet temps once the engine is up to temperature. Its typical to see around 15 to 20 degree gradient across a radiator when working correctly. Once it reaches its capacity and becomes saturated there will be no gradient.

If your engine oil temps are more than 10 to 15* above coolant temps I would consider adding a large engine oil cooler

Neal

The13Bats

2k cfm is not enough to cool a stock v8 according to what i have read on derale, spal, and flex lite websites,

In addition 30 plus years of wrenching also has me believing at the very least a stock v8 needs is 3k plus to cool,

However, fans are only needed at idle and low speeds,

Your car doesnt cool down while driving but rather gets hotter, something isnt right,

For example when i was doing some electric fan testing and temp would creep up at idle from not enough air flow driving would cool the car right off and that was an old wore stock radiator and mild engines both a 383 and 454,

Is there anyway the coolant flow is way too slow or blocked?

I hate to think that you have too small a radiator but it is one thing it could be,

I am assuming your timing is correct,

In the early 90s i daily drove a 66 custom, the engine was the 327 300 hp and fairly radical,

All i had for a fan was an electric off a gt fiero cooled great, turned off at speeds,
Then i was heading from orlando to jax to visit dad, the car kept creeping up, getting hotter than i liked, staying under 50 seemed okay,

My dad was a retired navy plane tech loved trouble shooting and we got busy, nothing helped and radiator flush made it worse,

So i buy a parts store replacement, can you believe a parts store had a mid year vette radiator...lol,

It worked cooler than ever,

My old radiator looked ok but was all worn out and plugged up on the inside,

I included that just to show the margin from cooling fine to overheating wasnt wide.

Big2Bird

What is your timing set up?

chevymans 77

Bat has touched on something that needs attention, a restriction in the system. The lower hose was collapsing and a spring was installed to prevent it. What causes a hose to do this?

There should be enough flow to supply the pump with the needed volume so that the pressure will not drop enough to cause the hose to collapse. The radiator cap is on the low pressure side of the system which should maintain pressure at or near the cap setting. Lets say that's 16psi then how does the hose collapse, lack of water volume for the pump. The op has posted that the radiator is new so what can cause the pressure drop in the lower hose, by installing the spring the low pressure didn't get addressed. We still don't know what pump he is using nor what brand radiator was installed. what size is the lower hose nipple?

The engine should/will be at a higher pressure than the cap as the pump will create pressure and the flow restriction through the engine along with the T-stat helps. Howard Stewart commented that the higher pressure you can run will help cooling and prevent hot spots along with in every test he performed the more water flow the more heat rejected.

Neal

ykf7b0

Based on my experiences I feel the sender for the factory gauge is inaccurate and the aftermarket is on par at 210 which is exactly what my 76 reads. I once replaced a factory sender with an Autozone sender and my factory gauge read 30 degrees higher. I would reinstall the thermostat as well.

Big2Bird

........... when you start the pump, there will be a differential pressure.
If you take a long, soft hose and apply suction, it collapses. That is why vacuum tubing has a thick wall, and long thin GM lower hoses had a spring.

cv67

Its happening at hwy speeds so rule the fans out
op do you have a good air dam underneath? WHen was the last time the fins were blown out with water they plug up bad

What lb radiator cap, have the correct one?
Getting sick of elec fans, have the 2200 spal even shrouded it ANY mech fan moves more air

chevymans 77

The hose will not collapse if there is adequate flow to supply the pump,

A hose with pressure will not collapse,

Neal

The13Bats

Very true,

Im curious have you tried letting the fans run and does it still overheat at moving speeds,
Tossing my guess yes it will still overheat and again tossing my guess at coolant flow, rather lack thereof,

However, if coolant flow is good and it still overheats at speed with fans on then i hate to say it but could be radiator is too small, defective or plugged up some way,

Are you sure water pump is good?

DUB

Geo.

the previous comment so what others feel should at least be considered.

But to answer this question due to no one has commented on it. I will say this from experience. On the Corvettes that had a clutch fan and the owner went to electric fans...and these electric fans are not running all the time. Consider the fact that the clutch fan was ALWAYS turning when the engine was running and moving air in the engine compartment at some rate.

SO...if you do not have the clutch fan...the air movement is debatable due to the angle of the radiator and your cooling fans and how they channel the air at a different angle/direction that what the clutch fan did...and YES...the underhood temps can get a bit higher.

Because if your car is running and are sitting still...and the electric fans are NOT on...how is the heat to get out if it no longer has a clutch fan to help get it out.

Also trying to compare your Corvette to a 1984-1996..which have electric fans...consider the fact that GM designed the fan support housing for the electric fan(s) to be vertical...and NOT at an angle. And yet the underhood temperatures...which do get high at times...are not blistering hot.

DUB

The13Bats

When at speeds the purpose of a fan clutch is to free wheel although i am told by many racers no fan clutch is 100% freewheeling so it becomes at speeds parasitic, enough to matter to most people, of course not, and if this is the case its not free wheeling 100% it is helping move air through the engine bay, but likely since not engaged its not helping much, and if 100% freewheeling its just spinning in the incoming air stream not helping at all, might even hurt a little since that air stream has to turn it,

A mech clutch fan needs to spin to move air, any fan does but it's locked to engine rpm, its actually not all that efficient at vehicle stop or low speeds where the fan is most needed for air flow and proper cooling,

The op is running electric fans, so clutch fans are moot.

A car shouldnt have the electric fans constantly off while sitting thats the time we want our electric fans on when there's no forward moment for airflow through the radiator to do its job, underhood temps is a side effect,

Of course While sitting the fans could turn off if the temp of the coolant is lower than temp of the fan switch,
while sitting
So it might get cool enough to cycle on and off at s stop, my 66 custom did that and my 87 fiero gt does it in cooler times of the year, but just sitting with no air flow its gonna warn up and kick on the fans, hence why at the very least electrics if working correctly will cycle at a stop, if needed dictated by their temp switch they will stay on,

While moving c3s have some flow through the engine bay, which i have always noticed c3s just seem hotter under hood that many other cars,

Sure exhaust adds to the heat but in all my time with vettes i have never seen a case of under hood heat being too high on a car that had a properly functioning cooling system, but we know that is not the case here, the op has a cooling system issue,

Personally i would worry about the cooling system first and when its right underhood temps will likely drop also.

DUB

I was commenting on WHY his under hood temps were so high and NOT the issue with the coolant temps. Which is why I only quoted that portion of his post only.

I hate to disagree with the previous post because every 1984 to 1996 Corvette does not have cooling fans running when it is sitting still. They come on when the temp is high enough. So having to have them running when siting still is not always the way it needs to be.....unless a person cares to argue with GM design.

I hate to also dispute the claim that at idle..and the car sitting still that if a person raises their hood and they have a fan clutch that the fan is moving a significant amount of air....and this is REALLY important if the car is equipped with air conditioning due to the air needs to be pulled across the condenser so the high pressure side does not get out of sight.

I am not worried about at high speed if or if not the clutch is working for the fan..becasue there is enough air coming across the radiator and into the engine compartment that this will aid in lower the under hood temps.

DUB

The13Bats

relax, i was just adding food for though.

This thread is about a c3 with aftermarket electric fans,

That was what my comment was related to, not c4s,
And i said the fans will come on when temps dictate it, i wasnt suggesting turn on fans with the ignition, i do perfer a temp switch to turn fans on,

i never met a c3 that could sit at idle and not eventually start to heat up then overheat with no air flowing through the radaitor

Most car people agree that if there is no air flow through a radiator they dont cool very well, but you say they do in c4s, so be it, then in this case c4s dont need fans at all.

You say the c4s never have the fans turn on at idle,

So they can sit it over 100 degree traffic indefinitely with no flow through the radiator and stay cool?

granted their electric fan switch is way higher than i like my engines running, but gm built it that way because they had to,
my fiero, same silliness, i changed the fan switch to a lower temp but didnt much matter i never turn the ac off,

My 86 corvette always had the ac on too so in turn that kicks on the electric fan so i ever tried letting it sit there for a while and see if it would stay cool at idle with no air flow,

As far as gm and c4 temps go, heres a nice read you will likely disagree with.

http://tech.corvettecentral.com/2011...modifications/

noonie

From the OP's info, he needs a new radiator, his is plugged up.
He should also do a serious block cleaning with proper acid and using the block plugs before removing the old one.

He said he's not familiar with these cars, so can't speculate on the underhood temps.

Dub is correct on the tstat operation, a hotter tstat simply restricts more flow than a colder one, and it doesn't take much.
The radiator of course has to be of adequate capacity and a working shroud with fans.

Howard Stewart of course is correct concerning flow, but the amount he is referring to is far beyond what is needed here and btw, flow looses its effect above approx 17ft/sec

Good luck emailing Howard Stewart, he has had nothing to do with Stewart Components for many years now, designed fuel pumps for a while in the Carolinas.

The13Bats

The op says the engine and radiator are new, so any blockage would be some weird defect, but i am sure its happened in some rare occasion,
and even so i bet its a rare long shot it sure does seem like this is in some way flow related problem be it coolant flow or air through the radiator, or perhaps both, the cooling system is just that a system,

A typical water pump can move about 7,500 gallons of coolant per hour, about a half gal a sec, sounds pretty fast to me, its a closed loop, it will cool if its an adequate system and is up to par,

Since i agree with stewart no need for me to email him and rant about he is wrong and i am right,

I also know some folks dont care if their temps get up 220 230 even higher, not me, i like to keep at or under 200,
Thats just me, im odd that way,

noonie

Didn't see the bit about the new rad and block.

Certainly sounds like a restriction to flow.

I would start as other has mentioned measuring the in and out temp differential of the coolant.

DUB

I talked with Stewart the other day and the tech guy DID comment on the variables and that there is no 'ONE FIX' for every application.

And as for using the restrictor washers...Like I asked them.. if a factory thermostat has a one inch hole in it when the thermostat is open...that a one inch hole in the restrictor washer is BAD. The only difference is that the restrictor washer will cause the coolant to take longer to heat up.


As for this article....I am well aware of the temperatures that the cooling fans come on and if some people feel that it is too high that is their choice.

DUB

chevymans 77

noonie, good to see you visit the forum

haven't seen you post in a while

Neal

noonie

Glad to see you too, car looking good.