LT5 Cooling and Radiators

[mike100]

You can successfully clean the radiator- especially if removed ( I did 4 years ago). Even the inside was free of corrosion and no reason it couldn't transfer heat as well as a new unit, but eventually the side tank seal will let go.

[5ABI VT]

Are the base c4 and ZR-1 rads exactly the same ? I can't recall if we covered that here I googled it and got mixed replies. Have a friend with a Dewitt for his 96 LT4 car he never installed and sold his car so he's willing to sel it to me cheap.

[-=Jeff=-]

Originally Posted by 5ABI VT

Are the base c4 and ZR-1 rads exactly the same ?.

Essentially yes

[secondchance]

Originally Posted by 5ABI VT

Are the base c4 and ZR-1 rads exactly the same ? I can't recall if we covered that here I googled it and got mixed replies. Have a friend with a Dewitt for his 96 LT4 car he never installed and sold his car so he's willing to sel it to me cheap.

Dewitt offers single row and double row. I went with the double row version and very happy with it.
http://www.dewitts.com/collections/c...minum-radiator

[secondchance]

Originally Posted by mike100

You can successfully clean the radiator- especially if removed ( I did 4 years ago). Even the inside was free of corrosion and no reason it couldn't transfer heat as well as a new unit, but eventually the side tank seal will let go.

I went through two OEM radiators. In my case both failures were stress crack on the driver side, about 4-5 inches from the top, resulting from heat, expansion and contraction cycling. Sort of similar to aircraft developing stress fracture on the skin due to pressurization/depressurization cycle.

[Livin' in the 80's]

Has anyone tried using a powerful back pack blower to blow out the fins of the radiator and the oil cooler and ac condenser?

[XfireZ51]

Originally Posted by Livin' in the 80's

Has anyone tried using a powerful back pack blower to blow out the fins of the radiator and the oil cooler and ac condenser?

Yes. It'll bend the fins

[QB93Z]

In my experience, the radiator fins become clogged with very fine sand. I had a radiator that was showing signs of insufficient cooling due to reduced air flow. I removed all the shrouds and the fans and fan assembly. Then I blew compressed air though the fins from the back using a stiff tubing with a right angle tip.

Then I removed the radiator and held it up to the sun and there were two circles (where the fans are) that let through less light than the edges.

I placed the radiator front down on the cement, lifted it about 6 inches and slammed it down on the concrete. On the cement, there were two circles of grit. I did this several times, then blew air through (backwards) and repeated.

I eventually got most of the fins cleared somewhat and reinstalled the radiator. I ended up replacing the radiator a few months later because I still felt that the air flow was reduced.

One good thing about removing the radiator was that I could straighten out all the fins that I bent using the pressurizer air wand.

Jim

[Billy Mild]

If the radiator is any age at all, just replace it with a new one. It is not worth cleaning it out. I cleaned mine and on installation the end tank failed. What a pain in the butt.

[Dynomite]

One item not discussed in this thread of which I have since experimented with is Engine RPM effects on Water Pump Flow and Engine Cooling.

1. Conditions

A. Fans turn on at 205 deg F and OFF at 200 deg F (Haibeck Chip)
B. I use 180 deg Thermostats.
C. Ron Davis, Dewitt, and Fluidyne multi core Aluminum Radiators.

2. My experience with Engine RPM (depending on Gear Driven 6th, 5th, 4th) in all ambient temperatures.

A. In sixth gear running 65 mph (less than 2,000 rpm) the Coolant always gets a bit over 200 deg F. On Hot days the coolant will get a bit over 213 deg F. The key is the Water Pump is not pushing enough flow through the fully open thermostat to cool the engine to a Temperature where the Thermostat takes over (180 deg F).

B. If I shift to 5th gear at 65 mph (more than 2,000 rpm) the coolant temperature drops to Thermostat control (180 deg F) on cool days and drops to near 200 deg F on Hot days.



3. Findings.

My findings are simply that the stock water pump is a bit low on coolant flow rate at rpms under 2,000 rpm. As you can see there is a big jump in Coolant Pump Flow rate between 1,000 rpm and 2,000 rpm and it is in this area or engine RPM that the Coolant Flow Rate is not sufficient in HOT Climates. This is specifically the overheating issue when idling at a stop sign on HOT days (100 deg +). If you raise the rpm from 800 rpm to say 2,000 rpm, coolant temperature will drop appreciably even though you are not moving.

The Coolant Pump Flow at 800 rpm is 15 gpm. The Coolant Pump actually gets more efficient as the rpm increases from idle to 2,000 rpm.

4. Water Pump Flow Rates.

As Per Marc Haibeck graph provided to the ZR-1 Net email list by Graham Behan about ten years ago, the Coolant Pump flow rate through the engine (not the radiator or thermostat) is:
15 gpm at 800 rpm
18 gpm at 1,000 rpm,
44 gpm at 2,000 rpm,
65 gpm at 3,000 rpm,
90 gpm at 4.000 rpm,
120 gpm at 5,000 rpm at which time cavitation is starting.

A. The Dual Thermostat Bypass pressure is apparently 5 psi and block resistance at 100 gpm is approximately 20 psi. I am not sure what the radiator Head Loss is at various flow rates but definitely depends on the radiator type.
B. It would seem that the Coolant Pressure Relief Cap on top of the Coolant Reservoir in front of passenger side set at 15 psi would assure the radiator maximum pressure would be 15 psi plus the Bypass Pressure of 5 psi or 20 psi.

See Item #5 The 180 deg versus the 160 deg thermostat or no thermostat