I'm Gonna Slash - Overheating Saga - Yes, Still!!!

[Oyaji]

Although a clean cooling system is certainly desirable, in my experience  (on all sorts of engines made over the past 70 years) residue at the bottom of the cylinder water jackets is of relative unimportance. Very little cooling of the cooling required to keep an engine at stable and efficient running temperature is provided at the cylinders - nearly all of it is provided by cooling the head. (In fact I can name at least one engine out there with no water jacket for the cylinders at all, having only the head water-cooled.)

.

To the point of your overheating woes - are you certain you are not lugging the engine? In other words, when you add throttle when running at the condition when the engine typically overheats, does the engine accelerate freely  - or only sluggishly or not  accelerate at all?  Additionally, what is your fuel economy in MPG? 

.

A lugged/overloaded engine will yield poor fuel economy and run hotter than normal, and in more extreme cases (perhaps in combination with other factors too) it will overheat beyond the capacity of the cooling system to keep up with the additional heat  rejection load placed upon it.  There are a number of possible causes for lugging, all of them related to the load demand that the engine is required to meet at a given operating RPM. As I  mentioned before,  a simple test for lugging is whether the engine can still accelerate while under load. If lugging is indicated, the next step is to find the cause; otherwise, the fault must lie with the cooling system (and considering all the diligent work you have done, that surely seems unlikely to me). 

[jimoshel]

This is true. But to get to the head the water must flow thru the block. If the block is stopped up, no flow to the head.

[cruiser54]

This is true. But to get to the head the water must flow thru the block. If the block is stopped up, no flow to the head.

Yup. Now is the perfect time to pull the CTS and flush the block.

[Oyaji]

This is true. But to get to the head the water must flow thru the block. If the block is stopped up, no flow to the head.

.

Good point. But typically, there is sump space below the water inlet to the block - is that not the case here? Further, scouring action *should* keep at least a channel open for normal/near normal flow...

.

Unless the engine has sat unused for some  time before being put back into service? Even just running straight water can cause problems over the long term, since antifreeze also incorporates an anti-corrosion additive. Electrolysis between dissimilar metals (brass radiators, cast  iron block, aluminum water pump are examples) joined by an electrolyte (water contaminated with ions from the metals previously mentioned) definitely adds to corrosion.

.

Can anyone recommend an "industrial-strength" uber-caustic radiator flush that strips rust/hard water/rat's  nest/EVERYTHING deposits from a cooling system? One that you  need to wear an apron, face shield, and elbow-length gloves to handle - so strong you dare not leave it in your system for more than a couple hours for fear of eating through the radiator core? Such used to be available, but I haven't been able to get hold of any since the mid-1970s. The stuff  was dangerous to handle (which is doubtless why I haven't been able to get it for years), but with hot water in a running engine it would pretty  much dissolve everything.

.

Prestone used to offer a back-flush kit that included a plastic tee-fitting  to splice into  a heater hose; you simply connected a  garden hose for flushing, and screwed on a cap in place when done. I guess it worked okay - are those still available? Back-flushing sure couldn't hurt... but I sure wish the OP would respond to the potential lugging issue in order to definitively rule it out before moving on.     

[cruiser54]

I have experienced the sediment in the galley. Clean water during a flush. Sediment only removed by removing block plug/CTS and flushing through water pump opening.

[Oyaji]

I have experienced the sediment in the galley. Clean water during a flush. Sediment only removed by removing block plug/CTS and flushing through water pump opening.

Roger that - good tip. Can you recommend any sort of jig or sealing method to get maximum flow and pressure when back flushing through the water pump opening?

.

But was the sediment load  in your engine(s) actually causing an overheating problem? Further, you can only get out just so much without stripping down the engine, scouring out all possible sediment mechanically, then finishing in a boiling caustic bath... and then sediment begins to build up again the moment the engine is put back into service. For this reason, over-capacity is designed in. I cannot speak to the specific design considerations of this particular engine, but I'd be surprised if it wouldn't perform up to specs with a great deal of sediment present. Consider: if this was a common problem, provision for regular cleaning would have been designed in from the start!

[cruiser54]

Got it all out through the galley plugs. Verified through the freeze plugs. Water hose through water pump opening.

[Oyaji]

Got it all out through the galley plugs. Verified through the freeze plugs. Water hose through water pump opening.

Roger - thank you.

.

But was that sediment you removed causing an overheating problem, or were you just being diligent in keeping your cooling system maximally clean?. 

[ParadiseMJ]

I have already removed the CTS AND the block drain and sent clear water thru it...nothing came out but clear, clean water.  The area I can SEE just behind the water pump is clean.  No rust, sludge, crap or otherwise came out...not even dirty water.  So as it sits the entire engine is flushed, but still no sign of any sediment anywhere.  So, blockage and/or crap in the block, the head, the core and the hoses is ruled out in my mind.

 

Any comment on the pump picture...or speculation the radiator.  The radiator has also been flushed 3 times without producing a bit of rust or crud.

 

And by the way, the CTS wires are crusty and kinked with a couple bare spots.  I don't think that's an issue but that will be replaced as well.

 

It CANNOT be this complicated.

[ComancheKid45]

It is possible that your just getting a bad reading to the gauge? Or have you verified the temperature with another source?

[Oyaji]

I have already removed the CTS AND the block drain and sent clear water thru it...nothing came out but clear, clean water.  The area I can SEE just behind the water pump is clean.  No rust, sludge, crap or otherwise came out...not even dirty water.  So as it sits the entire engine is flushed, but still no sign of any sediment anywhere.  So, blockage and/or crap in the block, the head, the core and the hoses is ruled out in my mind.

 

Any comment on the pump picture...or speculation the radiator.  The radiator has also been flushed 3 times without producing a bit of rust or crud.

 

And by the way, the CTS wires are crusty and kinked with a couple bare spots.  I don't think that's an issue but that will be replaced as well.

 

It CANNOT be this complicated.

Any chance that some time in the past you forgot piece of rag/sponge/paper towel somewhere in the cooling system? Because  some sort of mechanical blockage is about the  only thing that comes to mind after all the work you have done so far.    You must be exasperated.   

.

You said you had 2 weeks of cool running before this problem resurfaced yet again. To verify - did you try dropping down a gear to make up for the swap to AW4 transmission along with stepping up to oversize tires while retaining the stock 3.07 final drive?

.

Finally - have you had a look at your sparkplugs? How do they compare to the pictures in this chart?

.

http://3.bp.blogspot.com/-s_xxuAIEOpI/UY05gi55M1I/AAAAAAAAA_k/TGWSnNiGEaM/s640/Spark+Plug+Reading.jpg

[Oyaji]

It is possible that your just getting a bad reading to the gauge? Or have you verified the temperature with another source?

Indeed - thermometer in the radiator to calibrate/verify dash temp gauge may solve everything!

.

Reading back, one further clue I just noticed:

 

And by the way, the CTS wires are crusty and kinked with a couple bare spots.  I don't think that's an issue but that will be replaced as well.

[ParadiseMJ]

The wires were freshly exposed, likely I twisted them too much while removing the CTS yesterday.  I replaced the CTS back in 2011 when I was putting the truck back together just as a matter of course.  I don't believe it's been running that way.  My plugs look new...as in brown/tan with no gunk, in the good to better range per the chart.  They're gapped and re-gapped at .35 and they are only a year old.  I verified the temps with my HF IR gun on the first go around.  When the gauge is at 210...it reads ~200+ at the t-stat.

 

...and I AM exasperated, but that's not the word that comes to mind.

[Oyaji]

The wires were freshly exposed, likely I twisted them too much while removing the CTS yesterday.  I replaced the CTS back in 2011 when I was putting the truck back together just as a matter of course.  I don't believe it's been running that way.  My plugs look new...as in brown/tan with no gunk, in the good to better range per the chart.  They're gapped and re-gapped at .35 and they are only a year old.  I verified the temps with my HF IR gun on the first go around.  When the gauge is at 210...it reads ~200+ at the t-stat.

 

...and I AM exasperated, but that's not the word that comes to mind.

That temperature sensor to which you refer - it is the one for the fuel injection, isn't it? If that was a problem and it was causing you   to run too lean, you would know it from reading the sparkplugs - so that sensor is eliminated as the cause of your problem.     Ditto for pretty much anything  resulting from your engine's running condition: going by the plugs, all is well there...

.

How about your fuel economy? You haven't mentioned that yet.

.

Nor did you yet mention if you had tried dropping down a gear, nor your results from the simple test for lugging I mentioned before. 

[HOrnbrod]

What's the HF IR gun read at the temp gauge sensor at the rear of the head?

[nitroxsteve]

Could your engine have something going wrong with the timing when under load causing the heat?

[ParadiseMJ]

Anything is possible.

 

The plugs are good, the mileage is OK, 15+/20 town/highway.

 

Temp at head is about 240-250 when "overheating" and close to the red on the gauge.

 

Have good acceleration going up the hill in 3rd.  Not so good in D, until I punch it and it downshifts (kicks down), but when I know it's going to be pushing it I'll manually shift to the lower gear.  When I was driving it around the last 2 weeks it was mostly under 45 mph except for a short trip to the dump, with a trailer...only got a bit warm.  When I was blasting up the highway at 60-70 is when it was overheating.

 

...any comment on the water pump??

[Oyaji]

Anything is possible.

 

The plugs are good, the mileage is OK, 15+/20 town/highway.

 

Temp at head is about 240-250 when "overheating" and close to the red on the gauge.

 

Have good acceleration going up the hill in 3rd.  Not so good in D, until I punch it and it downshifts (kicks down), but when I know it's going to be pushing it I'll manually shift to the lower gear.  When I was driving it around the last 2 weeks it was mostly under 45 mph except for a short trip to the dump, with a trailer...only got a bit warm.  When I was blasting up the highway at 60-70 is when it was overheating.

 

...any comment on the water pump??

But the main questions   are still unanswered. When you were     "blasting up the highway at 60-70" "when it was overheating", had you dropped a gear (moved the shifter to the "Drive 2" position) or were you blasting along in top gear/overdrive? Is your speedometer corrected to show your  true speed - or is it  uncorrected and reading low? And what is your RPM at corrected/true cruise speed of ~65mph?. 

.

Remember in your other overheating thread when I asked you to try dropping down a gear? I meant not to use top gear/overdrive at all, and just to drop down a gear all the time you are driving from now  on until when you get around to regearing, to help make up for the estimated ~30% gear change you have done by fitting oversize tires and stepping up to the AW4 (which in stock gearing uses a 3.55 final drive) while  retaining the 3.07 final drive ratio. Aren't you running 33" tires? I reckon you should be running at least 4.10 final drive ratio - maybe 4.56 if you are running aggressive  tread tires (rolling resistance much increased) and a lift kit (aerodynamic  drag load increased). Are you also running a light bar or roll bar with add-on lights? Maybe also bigger mirrors for trailer towing? Extra-wide fender flares? All those things will add to aerodynamic drag too - and your engine cannot be expected to deliver power on tap at any RPM to satisfy the additional load. You are asking your engine to deliver more power at less RPM - and that is probably lugging it and causing it to overheat.

.

One comment on the water pump - are you running 50/50 water/antifreeze mix or just straight water at the present time? The surface rust/rust deposits look odd to me, as if you are maybe running straight water until you get your cooling problem sorted out. If so, I don't think it is a big deal (though running straight water long-term might be, simply because of corrosion concerns).

[nitroxsteve]

I can't add much to the water pump its sounds good. The only experience I have had with a water pump that looks good but was not was on some old John Deere engines after rebuilding the pump and reusing the impeller. When the engine was hot the impeller would start to slip on the shaft and the flow would drop. You could see this when you pressed the impeller off there were marks on the shaft. If this was happening to your pump you may see it on the shaft but you will destroy the pump to find out. On the pumps I was rebuilding its an iron impeller and we always used a new impeller to avoid this. I don't know if this is even possible to happen on your pump but its a thought.

[HOrnbrod]

Water pump comments? It looks fine and is stamped R on the impeller vane for the correct ccw rotation looking at it from the front. You haven't changed any pulleys recently on the serp belt drive to change the rotation RPM of the H20 pump have you?

 

You're not getting enough flow through the system for whatever undetermined reason at higher RPM as you know Charlie. There's alway the option of a Hesco High-Flow pump. Expensive option, but it seems like you have exhausted every other possibility.

 

[ParadiseMJ]

No Heater Control Valve

Does it matter which heater hose goes from/to the t-stat/water pump...top or bottom. Which way does the flow go? t-stat to heater to water pump OR water pump to heater core to t-stat?

[HOrnbrod]

This is the way they should go. I used the molded heater hoses and there's only one way to install them. But I don't think it makes any difference except change the coolant flow direction through the heater core.

 

[Keyav8r]

The hose arrangement Don shows (which is a whole lot cleaner than mine) is reversed from the way the hoses run on my 88.  The hose from the thermostat runs to the lower heater core connection and to the pressure bottle.  The hose from the water pump runs to the upper heater core connection.

There is a photo of the hose arrangement in the DIY section under "Informative Pictures Thread".

[Keyav8r]

http://brackmann.org...ep/miscinfo.htm

 

This is the link shown for the hose photo.

[Keyav8r]

But the link doesn't work, just tried it. The photo is on the first page of the random informative pictures thread.