High Volume Water Pump GM6-012-3
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High Volume Water Pump GM6-012-3 From applied
Am I overheating?
- Thread starter Kelpiesgmc
- Start date
High Volume Water Pump GM6-012-3 From applied
The "Superior" Radiator has a hole for its own thermostat apparently. I haven't installed one yet but was thinking of putting one in to monitor its temperatures as well as the engine temps. I think its 1/8 NPT and has a bung in it by default - you could put an additional gauge on that and see if both temp locations go up in parallel maybe. Might provide further diagnostic data.
High Volume Water Pump GM6-012-3
We are a major supplier of GMC Motor Home, RV Parts. Serving GMC MOTORHOME owners everywhere.www.gmcrvparts.com
High Volume Water Pump GM6-012-3 From applied
That's the right pump for the normal V belt setup, looks like a FlowKooler 1775
I think your next step is this:
Check your hoses. My upper hose got soft when hot and collapsed, causing an overtemp situation. The end result was a blown engine. Make sure you trim the hoses as necessary to prevent collapse. It's hard to see a kinked hose as it travels from the radiator under the firewall to the engine.
A quick question. When its showing these extreme temps and you shut it off, does it boil over?
That is what I would expect and what I've seen on my rig.
Rule of thumb that I got as a newbie mechanic is "If there is coolant in the engine, it's not overheating".
Point being the engine damage occurs when there is no coolant at the hot spots.
Where are you measuring the coolant temp? Can verify that the return line to the radiator will typically be at least 20 deg F hotter than what the guage will show with sender in normal position.
That is what I would expect and what I've seen on my rig.
Rule of thumb that I got as a newbie mechanic is "If there is coolant in the engine, it's not overheating".
Point being the engine damage occurs when there is no coolant at the hot spots.
Where are you measuring the coolant temp? Can verify that the return line to the radiator will typically be at least 20 deg F hotter than what the guage will show with sender in normal position.
Yeah, after shutting down the heat will go up as the water soaks all the heat out of the engine and there will be boiling coolant in the overflow. Sometimes it'll boil over and spill. Turning the motor back on and it'll cool back down very quickly to 220°
I'm measuring with two sensors (one mechanical) at the two ports at the front of the intake manifold.
I'm going back to suspecting air in the lines somewhere. I thought it was odd the heater wasn't getting hot so I took off and inspected the control valve for the heater core. It was working perfectly. So I ran the motor and pulled the top-most hose where it enters the heater core. It took a while, but eventually water flowed out and I quickly put it back on the heater core fitting. Now the heat works! I drove for about a half hour and temps were 220° at the hottest! They weren't growing constantly like before. Also the heat went down to 200° after reaching 220°— the first time it's been able to keep up with the heat.
After the drive I felt the hoses going back the the pre-heater in the bathroom and the return line was not even warm, so my next move will be to crack that while it's running (with a fill funnel hooked to the radiator to replace whatever gushes out)
Have you checked your ignition timing? Retarded timing can cause an engine to run hot.
Little update: Since breaking the lines at the heater core, and at the return line from the bathroom pre-heater, I've not seen the temps climb above 220º, and usually sits a little below that. I've been able to drive it around indefinitely, and the temps have remained very steady!
Now that my new engine is working, I can drive around again with all the problems I had _before_ my old engine blew up
Next up— drop the tanks and have them cleaned and lined. In my test driving I've been getting some fuel delivery issues. I have several fuel filters in the line (one before the aux fuel pump, one just before the mechanical fuel pump, and of course the filter in the carb.) Last night I was driving around and it kept loosing fuel— the filter before the mechanical pump looked like maple syrup. Super dark and cloudy. But hey!— I'm happy
Now that my new engine is working, I can drive around again with all the problems I had _before_ my old engine blew up
Next up— drop the tanks and have them cleaned and lined. In my test driving I've been getting some fuel delivery issues. I have several fuel filters in the line (one before the aux fuel pump, one just before the mechanical fuel pump, and of course the filter in the carb.) Last night I was driving around and it kept loosing fuel— the filter before the mechanical pump looked like maple syrup. Super dark and cloudy. But hey!— I'm happy
Great outcome! And nice looking gmc!Little update: Since breaking the lines at the heater core, and at the return line from the bathroom pre-heater, I've not seen the temps climb above 220º, and usually sits a little below that. I've been able to drive it around indefinitely, and the temps have remained very steady!
Now that my new engine is working, I can drive around again with all the problems I had _before_ my old engine blew up
Next up— drop the tanks and have them cleaned and lined. In my test driving I've been getting some fuel delivery issues. I have several fuel filters in the line (one before the aux fuel pump, one just before the mechanical fuel pump, and of course the filter in the carb.) Last night I was driving around and it kept loosing fuel— the filter before the mechanical pump looked like maple syrup. Super dark and cloudy. But hey!— I'm happy
View attachment 16694
Reworking the fuel lines is really not a bad job. The only real problem is the actual cleaning of the gas tanks, and cost of new senders.
But I see many owners struggling either fuel delivery because they dont really address the tanks and lines properly.
Well— I guess I celebrated victory too early 
No idea why, but when I was driving it around yesterday it shot up to 240º pretty suddenly. I pulled over right away and after a while of letting it cool I limped it back home. I had to stop several times as the temps just kept building.
Double checked timing this morning— I'm somewhere between 6º-8º btdc. the timing mark seems to slightly wonder +/- 2º.
I sprayed all over the place looking for a vacuum leak and I didn't find an obvious leaks. Maybe a tiny vacuum leak at the passenger-rear of the intake manifold, but not definitive. All vacuum hoses are new.
I got a head gasket tester kit that I'll try out next.
Feeling the all too familiar sting of defeat.
No idea why, but when I was driving it around yesterday it shot up to 240º pretty suddenly. I pulled over right away and after a while of letting it cool I limped it back home. I had to stop several times as the temps just kept building.
Double checked timing this morning— I'm somewhere between 6º-8º btdc. the timing mark seems to slightly wonder +/- 2º.
I sprayed all over the place looking for a vacuum leak and I didn't find an obvious leaks. Maybe a tiny vacuum leak at the passenger-rear of the intake manifold, but not definitive. All vacuum hoses are new.
I got a head gasket tester kit that I'll try out next.
Feeling the all too familiar sting of defeat.
Have you tried evacuating the entire system of coolant and then refilled so you know with 100% certainly that you don't have any air pockets? I personally have eliminated the heater hoses going to the bathroom water heater but that's just my personal preference.Well— I guess I celebrated victory too early
No idea why, but when I was driving it around yesterday it shot up to 240º pretty suddenly. I pulled over right away and after a while of letting it cool I limped it back home. I had to stop several times as the temps just kept building.
Double checked timing this morning— I'm somewhere between 6º-8º btdc. the timing mark seems to slightly wonder +/- 2º.
I sprayed all over the place looking for a vacuum leak and I didn't find an obvious leaks. Maybe a tiny vacuum leak at the passenger-rear of the intake manifold, but not definitive. All vacuum hoses are new.
I got a head gasket tester kit that I'll try out next.
Feeling the all too familiar sting of defeat.
At least eliminate/bypass them for testing. Simplify the setup to isolate the issue.
Have you checked to see if the upper or lower radiator hose is collapsing? I had similar symptoms on one of my vehicles and finally tracked it down to the lower radiator hose collapsing.
The hoses are all brand new and not collapsing.
I called S&J today and they had a good idea. Basically the idea is to run the hose from the heater return directly into a bucket and run the engine while simultaneously filling it until I've filled 6 gallons. That way I know I've completed "transfused" the system without introducing any air. I might cut out the bathroom lines for this as a test. I really like the pre-heater feature, but I like not overheating even more I suppose
I'll try the head gasket test first, then try the transfusion technique.
I called S&J today and they had a good idea. Basically the idea is to run the hose from the heater return directly into a bucket and run the engine while simultaneously filling it until I've filled 6 gallons. That way I know I've completed "transfused" the system without introducing any air. I might cut out the bathroom lines for this as a test. I really like the pre-heater feature, but I like not overheating even more I suppose
I'll try the head gasket test first, then try the transfusion technique.
The hoses are all brand new and not collapsing.
I called S&J today and they had a good idea. Basically the idea is to run the hose from the heater return directly into a bucket and run the engine while simultaneously filling it until I've filled 6 gallons. That way I know I've completed "transfused" the system without introducing any air. I might cut out the bathroom lines for this as a test. I really like the pre-heater feature, but I like not overheating even more I suppose
I'll try the head gasket test first, then try the transfusion technique.
I'm with @Tybalt39. For my sins I also have a GMC G2500 '89. It too was overheating - made worse by the fact that my dash gauge was unreliable.
I changed my gauge and then saw how hot it was running.
I bypassed both the front and rear heater cores it had entirely at the front and it solved my over heating problems. I have no idea what the problems were in those systems, I like you just wanted it to run cooler. So I say for purposes of simplifying diagnostics definitely bypass any rear systems for now to keep it simple. You can always add them back later.
Brand new doesn't mean much. There is some cutting that has to happen with brand new hoses to make them fit properly. @Tom Katzenberger ran into this issue specifically with a brand new hose that ended up collapsing without even being seen bec it only happened when the hose was warm.The hoses are all brand new and not collapsing.
I called S&J today and they had a good idea. Basically the idea is to run the hose from the heater return directly into a bucket and run the engine while simultaneously filling it until I've filled 6 gallons. That way I know I've completed "transfused" the system without introducing any air. I might cut out the bathroom lines for this as a test. I really like the pre-heater feature, but I like not overheating even more I suppose
I'll try the head gasket test first, then try the transfusion technique.
OEM hoses had a coiled wire "spring" inside to keep the hoses from collapsing. Many/most/all of them went walkabout sometime in the past 50 years. There're smooth bore hoses with corrugated outsides that are much more resistant to collapsing. In anything structural increasing depth/thickness increases stiffness.
I think @Tom Katzenberger 's hose wasn't "collapsing" as much as it was getting pinched due to it being too long. There's an amount that needs to be cut off the hose to make sure it fits properly.
I'm not sure about the particulars in Tom's case, I was commenting on all cases. GMC got the OEM hose length right, but they still put the spring inside the hose. Corrugated hoses are stiffer - go to an auto parts store and compare squeeze effort.
As always, your coach & your cash = your call.
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I too had the issue of the upper radiator hose collapsing. Only happened at higher rpm. Letting it sit idle slowed down the water pump which reduced the suction and allowed the hose to open up again, which made it hard to troubleshoot. Even revving the engine did not do it... It had to be at sustained highway speeds. After a minute or 2 on the highway, it would just slowly start to suck closed.
Typically, only the lower hose will suck closed, and I was already running the reinforced corrugated hose (the one Richard RV mentions above) on my lower so I did not think that was my issue. I only found it by driving around with the hatch off. I too was shooting a non-contact thermometer at parts of the engine and noticed the upper hose was flat.
Switching out the upper hose to the same corrugated design fixed my issue. I think the corrugated hose is a better option than the running a spring inside a stock hose, as the spring is integrated into the corrugated hose and surrounded by rubber. I've seen those springs on the inside of a normal hose corrode, and the pieces get sucked into places they should not be.
I also was running a flow-kooler pump, which I think actually exacerbated the issue as it created more suction when the thermostat was closed.
Typically, only the lower hose will suck closed, and I was already running the reinforced corrugated hose (the one Richard RV mentions above) on my lower so I did not think that was my issue. I only found it by driving around with the hatch off. I too was shooting a non-contact thermometer at parts of the engine and noticed the upper hose was flat.
Switching out the upper hose to the same corrugated design fixed my issue. I think the corrugated hose is a better option than the running a spring inside a stock hose, as the spring is integrated into the corrugated hose and surrounded by rubber. I've seen those springs on the inside of a normal hose corrode, and the pieces get sucked into places they should not be.
I also was running a flow-kooler pump, which I think actually exacerbated the issue as it created more suction when the thermostat was closed.
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