Single pass vs triple pass radiator

[paint2361]

My Pontiac 400 gets a little hot. Thinking of making my radiator a triple pass. Looking for some input. The motor is a Pontiac 406 alum heads. 10.5 cr. The cooling system is a huge be cool radiator with two spal fans and a full shroud running a high flow water pump. Wetter water with water only. On hot days the car gets to 230 or so.

[MuscleRodz]

We have a PRC dual pass on a 462 and runs ice cold. Fans only kick on with a/c or in traffic. I have yet to see it above 195 where the fans kick on. I would make sure you do not have any other issues causing the problem like an air pocket or maybe even timing before changing out the radiator. As far as the triple pass, I have not read that it works any better than a dual pass. Tube sizes get smaller to stay within packaging requirements and can't move anymore water than a quality dual pass with larger tubes.

[ehummelman]

I agree with Mike, I just had similar issues with my Pontiac stroker. It was driving me mad and after swapping out thermostats, purging coolant several times, and almost taking the waterpump off, I found that the issue was that the second high speed fan was not turning on when it should have. Blown fuse and needed to reprogram the SPAL controller to the right range for activating each fan. It stays at 190-200 now in Atlanta heat and traffic.

[paint2361]

I'm not going to replace my radiator just mod it to a triple pass. I would make a dual pass but the inlet and outlet are on opposite ends. I don't know what else would cause the high temp. We went through every part of the cooling system even the water pump. Whats the best way to flush out a alum. radiator?

[FlyDoc]

Maybe your water pump is moving the water too fast through the radiator to cool the water?

[dontlifttoshift]

Maybe your water pump is moving the water too fast through the radiator to cool the water?

From Stewart's website

A common misconception is that if coolant flows too quickly through the system, that it will not have time to cool properly. However the cooling system is a closed loop, so if you are keeping the coolant in the radiator longer to allow it to cool, you are also allowing it to stay in the engine longer, which increases coolant temperatures. Coolant in the engine will actually boil away from critical heat areas within the cooling system if not forced through the cooling system at a sufficiently high velocity. This situation is a common cause of so-called "hot spots", which can lead to failures.

[SparkyRnD]

it sounds like you have another issue going on, assuming that the radiator is clear and there are no obstructions. I would check timing, advance timing, fuel maps (if computer controlled) to check for a lean condition, et cetera. Also check air flow, and see if putting a fan or a blower in front of the fan at idle helps bring the temperatures down. Does it overheat whether at idle, going down the road or on the highway? Or just one / two of the conditions?

[dontlifttoshift]

230 is not bad if your gauge reads 20* too hot.....verify the accuracy of your gauge first.

[Tom Welch]

If flushing is a concern a triple pass radiator will be difficult to actually flush due to its design. I agree with Sparky concerning another issue causing the engine to run hot. Have you used an ifrared temp gauge? You know, the hand held laserbeam thing that reads temp? Try one to verfy the actual hose temps, there should be a noticeable difference between upper and lower rad hoses, if this is not the case maybe the thermostat is stuck, maybe the rad is clogged or the water pump impellar is damaged, gone or broken off of the shaft. You might want to check the water pump plates to see if the plate covering the impellar is close enough to the impellar to avoid cavitation of the coolant, you want about .030 clearance here.

[Tom Welch]

I just looked at your profile and it shows you have a 67 bird. Did you install the air diverter plates above and below the radiator? these will make a big difference in cooling capability since the air is directed at the radiator core and not around it.

[paint2361]

I just have the upper one on. I think I need to do a real good flush. My first engine kicked 4 rods and I got some oil into the water. I think I may have some crap in the radiator.

[MrQuick]

don't forget to check the rubber seals and plate behind the water pump.

[Tom Welch]

Yeah, like MrQuick said.

[paint2361]

When the engine was put together we used all new parts: flowkooler water pump with SS divider plate and sleeves. The divider plate was adjusted to close up the gap. My temp readings are pretty close, I have a fast ez efi and the handheld temp reading is pretty close to the auto meter reading. Are "BeCool" radiators any good? The one im using is from a 69 mustang. Its pretty big, it just barrley fit between the stock firebird subframe rails.

[19,69camaro]

Try reading this. http://www.pirate4x4.com/tech/billavista/Cooling/ Some of the best information I have seen so far.

[MrQuick]

Maybe your water pump is moving the water too fast through the radiator to cool the water?

That would depend on the context it was used. Argument, thermostat or no thermostat would be correct. The cycling between opening and closing is very fast but there is flow, more regulating, just not constant flow.

[paint2361]

For you Pontiac guys, does blocking off the heater ports (water pump and the back of the passenger side head) cause an overheat issue?

[Tom Welch]

The water pump bypass I believe is what you are referring to. The heater nipple on the rear of the pass side head as well. You can block these off but and alternative to aid in cooling the rearmost cylinders is to run a hose to each head and then back to the pump through the bypass tube, this will eliminate the heater from your system but can often increase cooling of the heads. Blocking them would'nt change much if anything. The hose you are referring to can be a good place to install a burp valve to ensure that air is purged from your system. Dont forget the lower air diverter pan below the radiator, on the original 400 and a/c cars these were used to improve airflow through the radiator, it does make a difference.

[paint2361]

I already blocked off the bypass. I think i'll tie the two rear head ports together and run it to the water pump bypass. Sounds like it coundn't hurt and might help. I also need to do a few good system flushes. Any good recommendations on a good flush/cleaner to use?

[tyoneal]

If you evacuate your system of air as you are adding your coolant, wouldn't that help eliminate a lot of other possibilities like areas of the engine that are trapping air and becoming hot spots?

Just wondering.....?