Cooling System Issues

[Justin Fleming]

Ok guys I am realy stumped here and hopefully it is just lack of knowledge. The issue that I am having is that my 86k5 is running at 210 -230 all the time. The system has a new HD single core radiator, new water pump, new thermostat, and new coolant. Here is what I beleive to be the issue. In all my other experience when you remove the cap and your rev the motor I have always been able to see flow out of the radiator tubes water falling into the tank once the t-stat has opened. This does not seem to be the case. I see zero flow through the radiator tubes. However I do see flow through the return line from the heater core which should indicate that the water pump is pushing water. When I pinch off that line I see no turbulence in the tank or flow from radiator tubes. The upper and lower radiator hoses are equal temps. At the thermostat hosing I remove one of the sensor to verify that coolant was making it past the thermostat. I am not lossing any anti-freeze due to leaks or anything like that. I beleive the only water exchange that I am getting is from the heater core exchange.



Please give me some help or ideas.....

 

[British Slave]

Thermostat in correct? Lower hose collapsing?

 

[jms]

Seems like the thermostat isn't working right...Not all 'new' thermostats are actually working. IIRC when I did this, the third one worked, and I had it in a pot with water on the stove first to watch it. All 3 were new in the box, from NAPA...

 

[wasted wages]

single core ???

 

[4X4HIGH]

Incorrect water pump. Could be for a serp set-up instead of V belts. The serp water pump is a reverse rotation.

Also i've never heard of a single core radiator before. I thought the smallest was at least a 2 core.

 

[michael0584]

Seems like the thermostat isn't working right...Not all 'new' thermostats are actually working. IIRC when I did this, the third one worked, and I had it in a pot with water on the stove first to watch it. All 3 were new in the box, from NAPA...

I've had the same problem with "new" thermostats. Always check it in boiling water before installing.

 

[samolson]

did you have this problem before is that why all the new stuff?

 

[Justin Fleming]

To reply to a few items.

-this is the second thermostat and I had checked both in boiling water
-I beleive that the water pump is turning in the correct direction as I receive the flow for the heater core exchange
-All the equipment is new just due to age and I did the maintenence

How ever I have also retro fitted a new stock 350 in the truck in lue of the old tired 305.

I begin to wonder if I have to correct temp sending unit? Is there a way to validate the gauge and is there a way to test the temp sensor?

 

[diesel4me]

Use a infra-red heat sensor gun to measure the temparature at a shop--or if your cheap,but an oven thermometer and stick it in the raditator and let it run to full temparature,and see what it says...I have had several GM trucks run at 220+ on the factory gauge,and NOTHING was wrong with them,it was the gauge or sending unit that was "off",they are often notorious for being innacurate...as long as its not boiling over and peuking out the overflow ,I'd guess its probably NOT overhearting..

 

[British Slave]

To reply to a few items.

-this is the second thermostat and I had checked both in boiling water
-I beleive that the water pump is turning in the correct direction as I receive the flow for the heater core exchange
-All the equipment is new just due to age and I did the maintenence

How ever I have also retro fitted a new stock 350 in the truck in lue of the old tired 305.

I begin to wonder if I have to correct temp sending unit? Is there a way to validate the gauge and is there a way to test the temp sensor?

General Motors 0-90 Ohm Gauge Diagnosis Procedure​

Especially as cars age, it is often somewhat difficult to pinpoint the root cause of instrument cluster gauge failure, thanks to questionable wiring, normal wear and tear, and sometimes even incorrect diagnosis procedures. The following diagnosis procedure is the method that GM publishes in it's shop manuals, will work on oil pressure, temperature, and fuel gauges, and should apply to all but the most recent GM-made vehicles with computerized gauges.
Before You Begin
You will need either Kent-Moore tool J-24538-A, if available, or tool JG-GM-1, a homemade GM gauge testing jumper. To build tool JG-GM-1, you will need the following materials:

• 1 Jumper wire with alligator clips (about $2 US from Wal-Mart)
• 1 220 ohm, 1/2W resistor (Radio Shack #271-1109, pack of 5, $0.99)
• 1 150 ohm, 1/2W resistor (Radio Shack #271-1111, pack of 5, $0.99)
• about 1" of 1/4" heat-shrink tubing, or vinyl electrical tape

Construct the jumper as follows:

1. Cut the jumper wire in half, and strip about 1/8" of the insulation off of the cut end of each wire. Tin the bare wires using a soldering iron.
2. Take both resistors and twist their leads together on each end, so that the resistors are joined in parallel. Twist the leads tightly, cut off the excess, and tin the twisted leads. If using heat-shrink tubing, make sure that the resistor assembly is about half the length of the tubing, or less.
3. If using heat-shrink tubing, slip the tubing over one of the jumper wire halves.
4. Solder each half of the jumper wire onto the opposite ends of the resistor assembly.
5. If using heat-shrink tubing, slide the tubing over the resistors and solder joints and shrink using a low-temperature flame or hair dryer. If using electrical tape, tightly wrap the tape around the resistors and solder joints, ensuring that the solder joints are completely covered.

Diagnosis Procedure

1. Disconnect wire from sending unit, and connect tool JG-GM-1 from the wire connector to ground.
2. Turn ignition ON.
3. If the gauge being tested reads at the high end of the scale (i.e. full for gas, 60psi for oil, etc.), the sending unit is at fault and must be replaced. Retest after sending unit replacement.
   Else, go to step 4.
4. If the gauge responds, but not accurately, go to step 5.
   If the gauge does not respond at all, go to step 7.
5. Disconnect engine harness connector at firewall bulkhead. Connect tool JG-GM-1 from ground to bulkhead connector lead that goes to gauge. If the gauge now responds accurately, check the wiring between the sending unit connector and the engine harness connector, repair any faults, and retest.
   Else, reconnect the engine harness connector, and go to step 6.
6. Remove the gauge from the instrument cluster and check the speed nuts holding the ceramic shunt across two terminals on the back. If they are loose, tighten them and retest gauge; if tight, the gauge is at fault and must be repaired or replaced.
   NOTE:You might be able to repair the gauge with a kit from Fix-A-Gauge, and/or you might be able to manually reposition the needle where applicable. Retest after repair.
7. Remove the instrument cluster and check for bad connections at the gauge terminal clips, instrument cluster connector, and both the instrument cluster and sending unit ground. If the connections are good, inspect the wiring from instrument panel to firewall harness connector, and repair any faults if found; if bad, repair the connections, reinstall gauge, and retest. If the connections and wiring are both good, the gauge is at fault and must be replaced.
   NOTE:A gauge diagnosed as bad through this step most likely can not be repaired.