Diagnosing overheat on D2

[kcabpilot]

No coolant in oil and prior to the overheat incident, which got to the point of illuminating the warning light, no I was not losing coolant. The reason I added coolant in Claiente was because it had boiled over. I will go about this systematically, the heads won't come off until I'm certain I need to go in there.

 

[kcabpilot]

More data to chew on:

Today I installed the new radiator, thermostat and pressure cap. I filled the system with distilled water through the raised expansion tank until it flowed out of the bleed screw. I started the engine and let it idle for about 15 minutes while monitoring the coolant temperature with my scanner. It steadily rose, when it got to 210 the electric fan kicked in but the temp kept rising. When it got to 225 I shut it down. All of the upper hoses were hard and hot. The lower hose and the entire radiator were stone cold.

So I'm sitting here scratching my head. I think I'll open a cold one and think about this for awhile. I at least deserve that.

 

[number9]

Ever flush/clean block with block drain plugs removed? Block holds more liquid and potential crud than the radiator.
......

 

[riceybean]

Might be time to pull the water pump. Maybe have a busted pump impeller? Can the heater core be bypassed to isolate that possibility?

 

[kcabpilot]

Water pump is less than three years old, has 20k on it. It was an OEM pump from Atlantic British, cost me $150. The whole system was completely flushed back in 2011 when I did the heads. The new thermostat is a Motrad 439-180. It was supposed to be a "soft spring" but it sure felt alot harder to push than the old thermostat.

Something's not working because obviously nothing is going through the radiator. I've never experienced a water pump failure of this nature. It's hard to even imagine how it could possibly do that, shaft is tight, no wobbles, no leaks.

The good news is that the block test came up negative. I'm just trying to formulate a plan of where to go to next. I guess it's possible I got a bad thermostat, that would be my luck, maybe I'll try putting the old one back in.

 

[kcabpilot]

Another update:

I put the old thermostat back in. At idle it got up to 210, the electric fan turned on and it stabilized there. When I ran it at 2500 rpm it stabilized at 188. After shutting down both upper and lower hoses were hot.

So it looks like I got a bad "new" thermostat.

I'm not out of the woods yet though, I still need to put the fan shrouds on and take it out for a real load test on the road. I'm keeping my fingers crossed, wish me luck.

 

[kcabpilot]

Still another update:

I took it out for a short test run. There are no hills near the house so I just romped on it to put as much of a load on it as I could. While moving it was stable at 195, at idle it sits at 204. The real test of course remains - climb a big hill. But it's close to 90 now and it still has the roof tent and all the other crap in it so it's carrying a load. I'm hopeful.

Tomorrow will tell....

 

[number9]

The new thermostat is a Motrad 439-180.

So it looks like I got a bad "new" thermostat.

Plenty of questionable reviews on the Motorad.

eurospare works good for me. Unless you want to spent the extra for the LR grey one.
http://www.rmeuropean.com/Products/PEM100990-MFG1110.aspx
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[kcabpilot]

I'd say this one is a definite failure so we can add that to the list. I bought it on Amazon so it's going back to where it came from tomorrow. When pushing on the bottom side with a screwdriver to check the bypass spring after I removed it, it was definitely jammed. I broke it loose but I could feel this grinding and binding when I pushed on it.

 

[JohnB]

Almost does sound like a water pressure issue. Not enough water pressure then the bypass will kill the flow from the radiator.
Like Peter said if the overflow hoses are blocked then flow would be slowed down thru-out the entire system.

 

[number9]

When pushing on the bottom side with a screwdriver to check the bypass spring after I removed it, it was definitely jammed.

FYI, Bypass valve/spring is in top center hole, not the bottom.
......

 

[kcabpilot]

We're probably just confusing terminology. I'm talking about the main spring in the thermostat body that releases when the engine rpm's increase and is instigated by the increased flow of the coolant created by the water pump. So it comes from the bottom and flows up to the suction of the water pump to flow through the block.

 

[number9]

We're probably just confusing terminology.

By pass is in top and a muck lighter spring not same as main stat spring that keeps it closed until heated up. You need to turn it upside down and take a look.

Illustration from:
http://web.tiscali.it/elise_s1/

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[kcabpilot]

Thanks. Yes I was talking about the main spring, my mistake. I just wanted to see if the thermostat was free to open.

Anyway I took the truck for a test drive today for about an hour. All seemed well, I drove around town and the temperature remained between 195 and 201. I took the back road to the nearest serious hill around here at Kirker Pass. Taking that route was about 35 miles and there were some modest hills but the temperature remained stable. But the minute I started up Kirker Pass it began to climb and by the time I got to the top I had an overheat light and was seeing 260 on the scanner. Unfortunately there was no way to turn around on that hill. I coasted down the other side and stopped at a parking lot to let it cool down. After about ten minutes I tried to make it back home but I could no longer drive even on level roads without it beginning to overheat.

Now for the weird part - I'm checking things and notice that while the upper hoses are firm and piping hot the lower hose and the entire radiator are cool. So I'm mulling over what to do and after about half an hour I look and there is no coolant in the expansion tank. I open the bleed screw and there is no coolant in the upper hoses. Fortunately in my premature confidence I had stopped and picked up a gallon of antifreeze and two gallons of distilled water and after pouring a little over a gallon of water into the tank it started to come out the bleed screw. I buttoned it up and drove home uneventfully.

So where did the gallon of water go? Oil level has not changed, in fact I drained a bit from the sump yesterday just to make certain there was no water in it. I never saw any steam or anything leaking and although it hit 260 nothing got past the new pressure cap.

None of this makes any sense to me but there has to be an explanation. For that much water to have gone through a head gasket you'd think I would have seen something.

 

[seventyfive]

as many times you've had the cooling system apart have you vacuum bled the cooling system?

The original post sounds like a flow issue/volume restriction.

But you've had it apart sounds like several times. You need to start with a vacuum bleed. And make sure I holds vacuum for at least 15 minutes. Until you do that you're wasting your time.

This last post sounds like you had a bubble.

 

[kcabpilot]

I guess it couldn't hurt to try, I'll have to order a kit but I agree with you, I really need to do this to find out what's going on.

I ran it again this afternoon with the pressure cap off to do another block test. As the temperature rose there were large bubbles coming up into the tank, after that the level began to rise until water began overflowing. When I shut the engine down, after it cooled a bit the water level in the tank dropped and the upper hoses were again filled with air.

Once again the block test was negative.

 

[jymmiejamz]

Once again the block test was negative.

Block tests can be very deceiving. A fail is definitely a fail, but a pass does not mean anything.

 

[number9]

The whole system was completely flushed back in 2011 when I did the heads.

I've never experienced a water pump failure of this nature. It's hard to even imagine how it could possibly do that, shaft is tight, no wobbles, no leaks.

Did your complete "flush" include removing block plugs? Did you use a product to clean block/system or just flush with water?

Others have suggested bad pump. Occasionally there's a defect and pressed on impeller no longer tight on shaft. Buy a pump gasket and check. It's a cheap easy step.
......

 

[kcabpilot]

Block tests can be very deceiving. A fail is definitely a fail, but a pass does not mean anything.

Yes this is what I've been thinking. It would be ideal to do it right when I got to the top of the hill but not really possible with a boiling hot system under pressure. Obviously when I'm idling in the driveway or even driving around town with stable temperature the problem, whatever it is, does not exist. I think I'm running out of options here and it's getting to the point where I'll probably have to start dismantling the engine. As I said earlier, whatever it is, I'm going to fix it. I'm not giving up.

 

[kcabpilot]

Did your complete "flush" include removing block plugs? Did you use a product to clean block/system or just flush with water?

Others have suggested bad pump. Occasionally there's a defect and pressed on impeller no longer tight on shaft. Buy a pump gasket and check. It's a cheap easy step.
......

When I get to the point of taking things apart I'll start there. As for the complete flush, yes plugs removed, no product used but that was 5 years and 40,000 miles ago and there had never been a problem until this incident in Nevada.