Help cooling issues urgent!

Cclaro

Member
Aug 1, 2020
20
3
13
20
FL
Just wrapped up a 351w swap. 205 11r heads, custom cam, the works. Car is ran off Holley terminator x timing at idle is between 8-10 degrees unlocked (adjusts timing for idle apparently it’s okay for it to vary slightly corrext me if I’m wrong.) literally everything in the bag is brand new minus a two year old sr performance radiator and pulleys. Fired up the car and this thing cannot maintain temp to save its life. Fans are derale dual 3600 cfm fans pulling plenty of air through the rad. I’ve tried a 180, 160, and no thermostat. No thermostat I was able to keep it at 220, the rest it would climb to 230 before I shut it down. Water pump is a Stewart stage 1 for a 95 mustang, belt Is routed correctly. Heater lines hooked up correctly, I have bled the system of air, tried filling coolant through thermostat neck, filled it through radiator, verified thermostats were opening. I am 100% positive head gaskets are on correctly and intake gaskets are aligned via arp intake studs with some rtv around the water jackets. As I run the car and watch the radiator with a thermostat installed I noticed there is very very little coolant flow both opened and closed. A very lazy swirl effect at best. Is it possible the pump is garbage and not circulating coolant at a fast enough rate? Possible radiator clog? I drained half the coolant and started the car and could see it circulating (still at a relatively slow rate). The pulleys are off a slightly modified 302 (edelbrock heads, e303 cam, edelbrock intake) and car never reallt got past half way on the gauge. Now that I have the Holley installed and can monitor expect temps it’s really concerning to see the new motor getting up to 230-240. I want to get it to hold at 180-190 in south Florida heat. Afr at idle is around 12.5, mapk is at 103 so there’s no vacuum leaks, fuel pressure is 43 psi. What do you guys think it is??? I know information is all over the place but I feel as if I covered all the bases of the cooling system minus the water pump. Help!!!
 
  • Sponsors(?)


7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
5,245
1,668
194
Kearney, NE
Tell us more about the water pump. Do you know what it is off of, and if it is for a reverse rotation, serpentine system? A pump off a V-belt year might fit, but the impeller is not going to work well backwards.
The other easy answer is the system needs burped of it’s air.
 

Cclaro

Member
Aug 1, 2020
20
3
13
20
FL
Tell us more about the water pump. Do you know what it is off of, and if it is for a reverse rotation, serpentine system? A pump off a V-belt year might fit, but the impeller is not going to work well backwards.
The other easy answer is the system needs burped of it’s air.
It’s a stewart reverse rotation pump for a 95 mustang brand new
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
20,164
6,816
203
polk county florida
Do don't sound excited about the difference, it should flow like a hurricane without the t stat, I would get the radiator checked and I would pull that water pump off, open the back and look at the impeller.
Oh, does the temp drop when going down the road or have you not driven it yet?
 

Cclaro

Member
Aug 1, 2020
20
3
13
20
FL
Do don't sound excited about the difference, it should flow like a hurricane without the t stat, I would get the radiator checked and I would pull that water pump off, open the back and look at the impeller.
Oh, does the temp drop when going down the road or have you not driven it yet?
Havent had the chance to drive it yet, might be looking at a new pump and rad.
 

7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
5,245
1,668
194
Kearney, NE
There could be something Stoopid in the engine’s cooling system like a freeze plug or bumper bolt. (Unlikely Stuff happens.)
I’d want to check out parts before replacing. This is a good excuse to buy a new tool. A temperature ray gun would help tell if coolant is glowing through just part of the radiator.
If the radiator is blocked by corrosion build up, it is often ugly to look at inside, but the zap thermometer will tell if only part is flowing.
Are the fans both moving the air the right direction? I ask because I have seen them wired to push from the back or one go each direction.
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
20,164
6,816
203
polk county florida
How many times do we hear ' oh the fan blade was spinning the wrong direction' or the blade on the back of the water pump was not spinning.
I want to know why it was overheating at idle, not that I ever really fix anything :doh:
 

KRUISR

5 Year Member
Apr 16, 2015
874
337
83
51
As the temps get up, do the fans come on? What is you fan set point? I know myself when I have reinstalled the rad and refilled, I can see the coolant flowing out of the rad tubes if I look in rad cap. Then after letting if flow for while (and fans cycle once or twice) I top up rad while running and close cap. Overflow tank takes care of the rest. A couple hours later after car cooled I top up overflow tank to proper level and call it a day.

On another item that I don't think is affecting your temps, 12.5 AFR seems awefully rich at idle to me, but I'm still running on factory computer (14.5-16 at idle while it warms up).
 

revhead347

Apparently my ex-husband made that mistake.
15 Year Member
Jun 14, 2004
8,898
1,520
214
41
Acworth, GA
Cooling on the SNs is notoriously bad. My car creeps up too.

First off, get a Mr. Gasket high flow thermostat. Last one I bought was at Advance, and it was cheap. It's one of those dangling packages on the performance aisle. It's a life saver, and makes a huge difference.

Your other options are to get a bigger radiator and a high flow water pump. The cross section on the SN radiator is small, and it causes cooling problems. I'm at 2" of radiator, and if the car sits in the heat with the AC on, it will creep up to 220 degrees. Unfortunately SN radiators are expensive too. We put a 3" Griffin on my friend's Cobra, and it has no cooling problems. For the high flow water pump, there is a Flowkooler that Summit sells, and it's reasonably priced. All of the Stewart SN pumps are factory flow, there is nothing special about them.

Kurt
 

Cclaro

Member
Aug 1, 2020
20
3
13
20
FL
How many times do we hear ' oh the fan blade was spinning the wrong direction' or the blade on the back of the water pump was not spinning.
I want to know why it was overheating at idle, not that I ever really fix anything :doh:
Fans are pulling air through the rad, I actually double checked my temp sensor to find it reading about 30-40° too high.
 
  • Like
Reactions: 1 user

Cclaro

Member
Aug 1, 2020
20
3
13
20
FL
As the temps get up, do the fans come on? What is you fan set point? I know myself when I have reinstalled the rad and refilled, I can see the coolant flowing out of the rad tubes if I look in rad cap. Then after letting if flow for while (and fans cycle once or twice) I top up rad while running and close cap. Overflow tank takes care of the rest. A couple hours later after car cooled I top up overflow tank to proper level and call it a day.

On another item that I don't think is affecting your temps, 12.5 AFR seems awefully rich at idle to me, but I'm still running on factory computer (14.5-16 at idle while it warms up).
Fan temps can be set to whatever I want so I played with a bunch of different points for them to come off and on, however the faulty sensor made the Holley believe it was always at 200+ degrees so they never turned off
 

Cclaro

Member
Aug 1, 2020
20
3
13
20
FL
Cooling on the SNs is notoriously bad. My car creeps up too.

First off, get a Mr. Gasket high flow thermostat. Last one I bought was at Advance, and it was cheap. It's one of those dangling packages on the performance aisle. It's a life saver, and makes a huge difference.

Your other options are to get a bigger radiator and a high flow water pump. The cross section on the SN radiator is small, and it causes cooling problems. I'm at 2" of radiator, and if the car sits in the heat with the AC on, it will creep up to 220 degrees. Unfortunately SN radiators are expensive too. We put a 3" Griffin on my friend's Cobra, and it has no cooling problems. For the high flow water pump, there is a Flowkooler that Summit sells, and it's reasonably priced. All of the Stewart SN pumps are factory flow, there is nothing special about them.

Kurt
Hopefully it was just the temp sensor, I shut the car off and after 5 minutes when we checked with a few thermometers to verify we only saw temps of 165
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
20,164
6,816
203
polk county florida
I may also help to reset the computer, disconnect the batt terminal for 15-20 minutes the run the engine up to operating temp, drive it around and let the computer get some fresh info then check for codes again.
Keep in mind the computer works best within a temp range, 165* may be at the 'not warm enough' range.
 

Cclaro

Member
Aug 1, 2020
20
3
13
20
FL
I may also help to reset the computer, disconnect the batt terminal for 15-20 minutes the run the engine up to operating temp, drive it around and let the computer get some fresh info then check for codes again.
Keep in mind the computer works best within a temp range, 165* may be at the 'not warm enough' range.
The Holley wants to see over 160 to enable self learning, gonna try to run it at 170-180
 
  • Like
Reactions: 1 user

KRUISR

5 Year Member
Apr 16, 2015
874
337
83
51
Don't forget the factory t-stats were 195. Don't be afraid of 180. Its called a motor up to temperature. This is where they are intended to operate.

My fans don't come on until coolant temp leaving the rad is at 205 (temp sensor in lower rad hose). When driving (moving) my fans NEVER come on.
 
  • Like
Reactions: 1 user