1. While water pump has some suction, it may not have enough to lift water much distance. If it had a lot of suction it would collapse hoses. Would want water constantly supplied to pump by gravity or hose pressure.

2. Boat motors tested this way are run at idle only, WOT (wide open throttle) is not advised because on a boat motor you have a ram pressure effect of 40 mph through water that garden hose does not match.

3. Without some kind of tester (IR thermometer or digital guage) this might cause more problems before you realized it.

4. Since we don't have flow GPM charts for water pump, and pressure guages, I would assume that pump is working. At some point, due to age, you will want to replace it, about $50. Many times the bad fan clutch holds hands with the water pump as they jump off the cliff. Both are turning, one wears against the other, etc. See pix of old water pump, begins to wobble, leaks, etc. I fixed my overheating by repair the radiator months before this pump gave up. So a worn pump may impact it, but not as much as your clogged radiator.

5. Perhaps another method would be to use a garden hose to provide a steady stream of cold water across face of radiator, providing more cooling than just air flow. But again you would want to monitor with a digital device of some type.

6. The fan clutch is only one problem, and it only has impact at low speed or parked. At 50 mph, if over heat, it is not the fan. As example, try holding a pizza box vertical outside the window while driving - lol - but that is the kind of air flow that radiator has. But the fan clutch does keep you from testing at idle, unless you have a really powerful shop fan.

7. If you open the fill hole on the radiator, and shine a flashlight in there, you can see the edge of some of the tubes. If gunk on them, it will be worse as you get to lower rows. Also, radiator (with truck run to operating temp then switched off) should not be hot/warm only at top. If much colder on lower surfaces, indicates no hot water getting to those rows of tubes. You'll have to reach behind fan blades.

8. You may get some indication of radiator by doing a reverse flush (lower outet to upper outlet, usually you will see flakes of scale coming out. That's just the tip of the iceberg. But home techniques, like white vinegar or even lay radiator flat on bench and pour muriatic acid inside will not get the results of the commercial hot acid flush (it is pumped through radiator) and rod out.

 

I agree - never thought about the actual GPM flow of a water pump. Also, never thought about the fact that the waterpump is gravity assist b/c the top of the rad is higher than the pump intake. That being said, could definately simulate these results with a bucket on top of the rad but probably more effort than its worth. The previous owner said he replaced the water pump which is supported by the fact that it looks new and the rest of the engine looks horrible (covered in sludge). Also, he got a new expansion tank (it is the clear one and has a date of 2010 on it). I think he tried replacing all the chepaer/easy parts in hopes that it would fix the rad problem and then gave up.

For now I will assume water pump is okay and will confirm by removing the plastic rad plug - if I shine a light from other videos I have watched on the Disco 1, I should be able to see the fluid spilling in the rad once the thermostat is open - the implies flow and should confirm the water pump is working. Following this, I am going to do the following:

1) Pull rad and bring to shop to confirm flow and repair/replace as necessary.
2) Get Chevy fan clutch and replace (this will allow me to continue to diagnose the problem without having to drive the truck on the road and needs to be done anyway)
3) Get chemical exhaust gas tester and test for this in the coolant gas coming out to determine if there is an internal engine problem - i.e. cracked block/head gasket.
4) Test compression to see if this provides any indication of internal engine problems.
5) If 3 + 4 show problem, I will pull engine, disassesmble and inspect and repair/replace as necessary.
6) If no issues are noted in 3 + 4 I think I can conclude that the problem must be rad, water pump, fan, leak in system (ie hoses), plug in coolent routing within engine, or combination of some of these.. I will test each and see what I can uncover.
7) After 6, I will probably still pull the engine and rebuild/replace worn parts even if we get the overheating under control ... There is a resonably big oil leak that I don't like and therefore need to replace gaskets anyway which is easier on an engine stand. Also, if I am going offroad in this truck I would feel better about doing so with a 15 year old engine if I have seen for myself there are no internal problems.

That way I only have the transmission, transfer case, drive shafts, differentials, suspension, steering, running out of gas, getting lost and getting eaten by a bear to worry about.

 

Where is oil leak? Usually there are many oil leaks. A common one is valve cobver gaskets, snug up each oil change with 8mm 12 point 1/4 inch drive socket.

Obviously the pump has some suction, but it would not be like a swimming pool pump.

 

Both of my oil cooler lines were leaking very badly. The hoses themselves failed and were dripping oil about one drop per 2-3 seconds at idle! Fixed on the cheap in my case but could be a source for your leak(s).

 

1/4 drive 5/16 12 point sockets (regular with extension or deep) are easier to find than the 8mm. They also fit better and are often cheaper.

 

As for overheating: What about unplugging A/C compressor that way when the A/C is turned on, the fans just come on to help with cooling when doing tests? Since the fan clutch is MIA. Just a thought.

 

AC fan trick is a good one, but IMHO they only provide about 30% of what the main fan does. More worried about testing for overheating by depending on stock temp guage as the reference point.

 

Interesting AC fan trick - I will keep that in mind.

As far from leaks the engine bay is a mess so no clue - TBO I am not going to worry about a leak until I am confident I have a salvagable engine and can get the overheating issue under control and for me to feel comfortable with the engine being okay I think I need to take it apart and inspect.

And if I am taking it apart, I replace the gaskets and therefore should solve the oil leak problem by default anyway.

This is obviously jumping the gun abit as I am not going to put any time or money into the truck until I have diagnosed the cause of the overheat and have confirmed I can salvage/repair the engein - i.e. no cracked block or other $$$ bottom end problem.

 

Found a spec on the water pump -

Coolant pump output at 1000 rev/min 10 litres/min (2.64 US galls/min) at 0.7 bar (10 lbf.in2)

So should fill a 5 gallon pail in just under two minutes. But it does not have 5 gallons inside to start with...

 

Interesting ... so it is feasible ....

Just would require a 5 gallon source bucket with a garden hose to keep it filled and either 2 drain buckets to keep swapping out and dumping or a wet garage floor...

Kinda a cool way to diagnose a broken rad.