Help! 69 Overheating - Big Block

[edevince]

Hi CAC team

need your help. 69 is overheating at idle and low speeds.....ok on highway.

radiator had leak repaired and flow checked, both ok.

new 160 thermostat installed. Fresh antifreeze.

has electric fan in front of radiator.

overflow tank has sufficient coolant in it

dont know where to go next to get it resolved. Please help!



Ernie

 

[stevolwevol]

Hi CAC team

need your help. 69 is overheating at idle and low speeds.....ok on highway.

radiator had leak repaired and flow checked, both ok.

new 160 thermostat installed. Fresh antifreeze.

has electric fan in front of radiator.

overflow tank has sufficient coolant in it

dont know where to go next to get it resolved. Please help!

Ernie

Your engine is running cool when going fast enough for air to get pushed up by your air dam, but it's over heating while idling.

Your water pump, and radiator must be working, or it would be over heating all the time, so your fan must not be doing its job. Do you have a fan shroud? It is likely the fan, or the setup.

 

[Hib Halverson]

Your problem is likely cooling air flow not coolant flow.

Here are some things to check

1) Stock front air dam in place and functional.
2) Fan clutch faulty?
3) Fan shroud in place and functional
4) Stock sponge rubber radiator seals in place.
5) Make sure the aux. fan is blowing the right way, also aux. electric fans which push rather than pull are not as efficient.

 

[Vettehead Mikey]

How do you know it's actually overheating? What temp are you seeing on the gauge?

 

[stevolwevol]

Your problem is likely cooling air flow not coolant flow.

Here are some things to check

1) Stock front air dam in place and functional.
2) Fan clutch faulty?
3) Fan shroud in place and functional
4) Stock sponge rubber radiator seals in place.
5) Make sure the aux. fan is blowing the right way, also aux. electric fans which push rather than pull are not as efficient.

Mikey, I am curious about number 4. How does a faulty rubber radiator seal affect temps, as long as the shroud/fan is working?

OP, did you replace the clutch fan with the electric one?

 

[Hib Halverson]

Mikey, I am curious about number 4. How does a faulty rubber radiator seal affect temps, as long as the shroud/fan is working?

OP, did you replace the clutch fan with the electric one?

Strips of sponge rubber were used to seal the radiator to the core support and to the hood. They prevent cooling air flow from bypassing the radiator. Since your problem is air flow, not coolent flow, it might be good to check them or reinstall them if they are not there.

 

[rep69]

I had the fan clutch removed and put an adapter that is direct drive. Pulls more air

 

[stevolwevol]

I had the fan clutch removed and put an adapter that is direct drive. Pulls more air

Having direct no clutch fan should cool just fine. Did it overheat before you put the electric fan on? If the electric fan isn't working properly, it might be blocking airflow.

 

[kpic]

Did it overheat before you put the electric fan on? If the electric fan isn't working properly, it might be blocking airflow.

Whenever a system is changed, the first question is did the change cause the problem.

 

[edevince]

So this is Ernie again.....from the original post.

I think you are right, it is air flow, not coolant flow.

The shroud is there but compromised. And some of the support and shroud seals are missing. So I am buying a new shroud and seal kit.

Is there a diagram out there that shows exactly which seal goes at which location?

Thanks guys


Ernie

 

[stevolwevol]

So this is Ernie again.....from the original post.

I think you are right, it is air flow, not coolant flow.

The shroud is there but compromised. And some of the support and shroud seals are missing. So I am buying a new shroud and seal kit.

Is there a diagram out there that shows exactly which seal goes at which location?

Thanks guys


Ernie

Sounds like a possible smoking gun. What about the electric fan? Is it blowing the right direction?

 

[Peer81]

Your problem is likely cooling air flow not coolant flow.

Here are some things to check

1) Stock front air dam in place and functional.
2) Fan clutch faulty?
3) Fan shroud in place and functional
4) Stock sponge rubber radiator seals in place.
5) Make sure the aux. fan is blowing the right way, also aux. electric fans which push rather than pull are not as efficient.

When looking at Hib's things. At idle or slow speed:

1 and 4 make no difference if the is no or slow airflow. The fan clutch is a good idea and the auw fan right way even better. If would also say. When replacing the clutch fan and putting in a aux fan. Is it pushing or pulling more of the same air through the radiator as OEM? If you changed the clutch fan, is the new fan also it the right place for the fan shroud. If not I think this mismatch means the fan if not pulling all the air through the radiator as it could.
In short if it's mid 80's you're in a trafficjam and the engine is overheating not enough air is pulled of pushed through the radiator. Also, do you have a airco radiator before the coolant radiator, if so is everything clean between the two?

Greetings Peter

 

[kpic]

In short if it's mid 80's you're in a trafficjam and the engine is overheating not enough air is pulled of pushed through the radiator. Also, do you have a airco radiator before the coolant radiator, if so is everything clean between the two?

Greetings Peter

Well said!!!

I have an intercooler in front of everything else. In addition the installation required removing some of the stock body goodies and air spoiler. In stop and go traffic with a temperature of 95F/35C, the fans went to high speed. Even with a thick intercooler in front of everything else; no overheating that the OE fan and radiator couldn't.
Yes, since then I have sealed every "hole" and filled the removed OE body work to channel every bit of air I can through the radiator. No matter if I'm moving or setting still in traffic.. It works fine at 104F/40C without the fans going to high speed.m

IMO, the OP needs to fix/replace the compromised shroud first, see what happens and go from there...

 

[Otter]

**Off topic** Kpic, not sure what happened with your response to the "Aero" thread but just received an email notification with 15 pages of hexadecimal garbage...weird stuff..

 

[edevince]

Still need help - 69 overheating

Hi guys

thanks for all advice.....but i still have a problem. Overheats at idle and low speeds, ok at moderate and higher speeds. So i agree with everyone, it is air flow across radiator, not cooling flow.

here is the hardware situation:

radiator flow checked ok, not leaking

160 thermostat

NEW shroud installed

NEW shroud seals and radiator support seals installed correctly

front air dam in place and looks fine

it is a little better with new shroud and seals, but still overheats ( but takes a little longer). Gauge climbs from 100 up to 225/230 then i shut it down.

any ideas?


thanks


Ernie

 

[Hib Halverson]

Hi guys

thanks for all advice.....but i still have a problem. Overheats at idle and low speeds, ok at moderate and higher speeds. So i agree with everyone, it is air flow across radiator, not cooling flow.

here is the hardware situation:

radiator flow checked ok, not leaking

160 thermostat

NEW shroud installed

NEW shroud seals and radiator support seals installed correctly

front air dam in place and looks fine

it is a little better with new shroud and seals, but still overheats ( but takes a little longer). Gauge climbs from 100 up to 225/230 then i shut it down.

any ideas?


thanks


Ernie

225°/230° while, admittedly, somewhat high is not "overheating" in an engineering sense.

What ambient temperature is present when this happens?

You mention that the ECT starts at 100° and goes to 225°/230° at slow speeds...is 100° the nominal ECT on the highway?

More ideas...
Check temp gauge against known good gauge.
Faulty fan clutch?
Wrong cooling fan?
Restricted radiator?
aux. fan installed incorrectly?

 

[Tom Bryant]

Have you checked the temperature at the thermostat housing and upper hose when your gauge says 225-230 with an IR gun? Are you loosing any coolant out of the overflow? Could be that you just have a faulty sender or gauge.

Tom

 

[stevolwevol]

I still have to believe due to low speed, low idle overheating, you have a air flow issue due to your fan not pulling air through the radiator. How about the electric fan? Is it spinning the right way? My Vette is the opposite. I run cooler at low revs, and warmer (but not too warm) on the highway.

 

[1BAD80]

I would put in a 185* thermostat, the coolant needs to sit in the block longer to pull off the heat, also get some good aluminum duck tape and seal off all the front end /motor compartment. Royal Purple Ice coolant additive will help.
I painted over with black paint, made big difference with the air flow while in traffic
Also Hibs suggestions with the seals will help more.

 

[tnovot]

Overheating

Have you checked behind the air dam and/or at the bottom of the radiator for any trash that could have been picked up from the road which might be affecting air flow such as leaves, plastic bags, etc?