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  #31  
Old July 22nd, 2019, 09:54
trippled trippled is offline
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Re: Overheating solved

The heater control valve bypasses the heater core when ac is set to cold. Gives you slightly better ac performance. That's it.
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  #32  
Old July 22nd, 2019, 10:18
mhead mhead is offline
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Re: Overheating solved

Wow thanks for pictures under the thermostat housing.

So my model of the cooling system with the heater core shunting just the radiator isn't correct. I'll have to revise it, assuming coolant in the head is free to reach the thermostat as well as the port for heater.

Things are getting complex so I've placed a sketch of what the revised model is.

Revised model:



Question: is there any unusual flow in the head? Is fluid free to reach the heater port equally as well as the thermostat?

Mike
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  #33  
Old July 22nd, 2019, 10:20
mhead mhead is offline
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Re: Overheating solved

Well for some reason doesn't display my sketch. Here's a link

https://drive.google.com/file/d/1hDU...ew?usp=sharing

maybe this will work...

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  #34  
Old July 22nd, 2019, 10:50
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ehall ehall is offline
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Re: Overheating solved

Yeah the heater circuit is always open (regardless of the thermostat or heater control valve), allowing coolant to constantly move through the motor even when the thermostat is closed. Otherwise the coolant in the head would boil before the thermostat opened.
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  #35  
Old July 22nd, 2019, 11:06
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ehall ehall is offline
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Re: Overheating solved

Quote:
Originally Posted by mhead View Post
Question: is there any unusual flow in the head?
There are some weird passageways in the head, if you ever look at one you will wonder how all the air ever gets out. But nothing weird in terms of direction.

Quote:
Is fluid free to reach the heater port equally as well as the thermostat?
The thermostat and the port for the heater circuit are right next to each other in the housing. The pump is actively pushing fluid. When the thermostat is closed the least resistance is through the heater circuit into the valve and heater core. When the thermostat is open that path has a little less resistance due to the size of the radiator return hose (although resistance will quickly build up, at which point the path through the heater circuit is equal resistance).

Just as a sidebar I replaced the convoluted 4-port heater valve with an H-shaped tee and a 2-port valve on the heater circuit. When the valve is closed the fluid backs up and the path of least resistance is through the H-shaped tee upstream. When the valve is open fluid can flow straight through the hose and heater core, which has less resistance than taking the 180 turn through the H.

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  #36  
Old July 22nd, 2019, 15:56
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NXJ4CB NXJ4CB is offline
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Re: Overheating solved

Hello,
I haven't forgotten this thread. I appreciate all the input everyone has been giving. I've been tracking my temps this last week and found that it will run in the 220s unless I keep the heater bypassed. It ranges under load but tries to maintain 180 to 190 mostly.
Also, I read the temps at the radiator tanks and they are uneven. I believe there is a restriction in my radiator or its too restrictive by design. I've had two of these CSF three rows with the same results, and assumed they were both good.
I'm going to replace the bypass radiator and leave the valve in. My current theory in my case is still the same. Only a different a different radiator and more tests will really confirm that flow theory.
An added benefit of the heater bypass is my AC is more efficient now. Maybe my blend door leaks too but, that is for another time.
I'll keep reporting as I have data to provide.

Thanks,
NXJ4CB
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  #37  
Old July 22nd, 2019, 17:22
mhead mhead is offline
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Re: Overheating solved

Hi NXJ4CB,

Your "Also, I read the temps at the radiator tanks and they are uneven" - can you give a little more description of what this means? Where on tanks? Are these the side tanks that run vertically when radiator is in vehicle? Horizontal tank at the top? Bottom? How uneven? How do you read temperature at spots on these tanks? Interesting to explore heat distribution within the radiator.

Thanks!
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  #38  
Old July 22nd, 2019, 17:30
mhead mhead is offline
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Re: Overheating solved

And with respect to the heater core and heater control valve - I guess as someone mentioned previously that the weird heater control valve shunting feature is there to allow limited circulation during engine warm up and at other times when the thermostat valve is closed due to cold temps. Whoever designed this feature knew something I do not (easy thing...) about engine heat. So I have now come to believe that my plan of simply closing off flow in the heater core and eliminating the heater control valve may result in engine hot spots when the thermostat is close. Probably a bad idea.

But... the HC and HCV do shunt the radiator to the degree that coolant flows through them and not through the radiator. So ehall's shunt in the picture above is kinda scary since it is connected through hose length of only about 1/2 stock vehicle length and therefore shunts perhaps 2X the amount of the normal stock HC/HCV arrangement.

I'm going to have to re-think my HCV elimination plan to be more like ehall's.

Mike
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  #39  
Old July 22nd, 2019, 18:57
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techno1154 techno1154 is offline
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Re: Overheating solved

Quote:
Originally Posted by ehall View Post
Just as a sidebar I replaced the convoluted 4-port heater valve with an H-shaped tee and a 2-port valve on the heater circuit. When the valve is closed the fluid backs up and the path of least resistance is through the H-shaped tee upstream. When the valve is open fluid can flow straight through the hose and heater core, which has less resistance than taking the 180 turn through the H.

Interesting valve system. I like it although most/all seem to be plastic which I am always a little leery of,... breaking at the most in-opportune time.


The simple way to eliminate coolant going through the heater core while at the same time maintaining the flow when the thermostat is closed is to use a copper/brass "U" in the line out of the thermostat housing and the line going back to the water pump. Restrictors of plastic or metal could also be inserted into that line at the time.

On my XJ, that 4 way valve do not completely stop the coolant going into the heater core. Both hoses from the core and the valve exhibit a substantial temperature rise with the valve closed. I never gave it a second thought but simply accepting that there is a bit of internal leaks inside the valve. The valve do need vacuum to close it and keep it closed. I do like Ehall's method. Being from the Caribbean, I really hate the cold.


Many years ago, I had one of those 3 core radiators. My XJ ran hot with it. A scan revealed the radiator had different temperatures in unexplained places. I kept it 2 weeks then tossed it,...TWO weeks brand new.
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1996 XJ; 4.0L; AW4; NP231; SYE; D30 and D44; ECTED; 4.10 gears; 30X9.5 -15 BFG/AT/KO; 3" lift; Rusty's LCA; JKS ADJ UCA; Kevins ADJ Track bar; Drawtite Front Receiver; Dual Electric Fans; Dual Battaries.
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  #40  
Old July 22nd, 2019, 20:27
2X_01_Jeeps 2X_01_Jeeps is offline
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Re: Overheating solved

My '01 doesn't have any heater control valve at all (unlike the '84 I used to have).


I plumbed in a ball valve in the heater circuit and tapped across it to supply flow thru a coolant filter I've put in. The valve I put in is a brass ball valve (better at ON/OFF than common faucet type valves) I purchased at ACE hardware. I used plastic coolant T fittings from Carquest. (for use in coolant and high temps)



Using parts obtained from ACE and T fittings from NAPA one could fashion a bypass that you can control manually when you won't be needing heat but which will still allow circulation as if the heater core is present.



Just an idea.....
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  #41  
Old July 23rd, 2019, 02:04
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NXJ4CB NXJ4CB is offline
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Re: Overheating solved

Quote:
Originally Posted by mhead View Post
Hi NXJ4CB,

Your "Also, I read the temps at the radiator tanks and they are uneven" - can you give a little more description of what this means? Where on tanks? Are these the side tanks that run vertically when radiator is in vehicle? Horizontal tank at the top? Bottom? How uneven? How do you read temperature at spots on these tanks? Interesting to explore heat distribution within the radiator.

Thanks!

The measurements i read were, 160's at the top and bottom third of the tanks and the middle third roughly engine temps 200's. This was measured with an infrared thermometer going up and down the side tanks through the grill and not measuring the tube at all due to the condenser being in front of it. Discussions with smarter people tell me that the part of my radiator that is actually is the middle. The two thirds that aren't working are the stagnating cool areas.


I'm regretting the title of this thread. Definitely NOT solved! Yet! I've seen so many threads with no consensus on the solution. I was so happy when my temps went to normal I thought I have to spread the word...
Even if I haven't saved the world. At least this thread is out there and you gents are considering another angle I haven't seen in a forum yet.
I apologize for the misleading title. SOLVED is a big claim.


Thanks,
NXJ4CB
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  #42  
Old July 23rd, 2019, 02:17
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NXJ4CB NXJ4CB is offline
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Re: Overheating solved

Quoting Patrick here: "Many years ago, I had one of those 3 core radiators. My XJ ran hot with it. A scan revealed the radiator had different temperatures in unexplained places. I kept it 2 weeks then tossed it,...TWO weeks brand new."


I'm really wondering if this "common" combination of High flow pumps, high flow housings and 3 row radiator will just never work.
How do you define running hot?
Am I wrong thinking that any movement of the needle is abnormal? When my jeep was "new to me" and stock, I towed all my posessions from San Diego to Tuscon and back again and the needle never budged (June). It always stayed just shy of 210. I own this rig because I overheated my Toyota pickup and had to junk it.

Now the needle is all over the place, it doesn't boil over but getting above 215 I believe is NOT GOOD. The highest temp I recorded is 234.



NXJ4CB
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  #43  
Old July 23rd, 2019, 07:08
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Anak Anak is offline
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Re: Overheating solved

I don't think the needle should be all over the place, at least not in an XJ. My '95 Cummins is another story. But it is another animal.
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  #44  
Old July 23rd, 2019, 21:01
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techno1154 techno1154 is offline
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Re: Overheating solved

Over heat for me is when the needle get close to the red. Half way between 210 and the red line is cause for concern even when I am pushing it hard up hill.
My XJ usually do not go pass the 210 mark except when sitting in traffic in South FL. before I added an AW4 cooler. I have since change the temperature at which the fans come on and added a cooler to the AW4.

Keep in mind my XJ do not have a mechanical fan for 12 years.
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#594
1996 XJ; 4.0L; AW4; NP231; SYE; D30 and D44; ECTED; 4.10 gears; 30X9.5 -15 BFG/AT/KO; 3" lift; Rusty's LCA; JKS ADJ UCA; Kevins ADJ Track bar; Drawtite Front Receiver; Dual Electric Fans; Dual Battaries.
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  #45  
Old July 31st, 2019, 12:27
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Greenspan Greenspan is offline
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Re: Overheating solved

On thing to keep in mind is the temperature needle on the dash is not very reliable. It'll stick at around 210 even when the Jeep is actually in the 220-230 range and then suddenly peg hot around 240. I think this was done to prevent the average Joe from panicking over the jeep warming up a bit but let them know when there really is a problem. You need to hook up an OBD reader if you want to see the true temp.

From a fluid dynamics perspective I don't think your theory makes sense. The high flow coolant pumps increase output pressure which in turn will increase flow rate through whatever restriction are downstream. Right that restriction is split between the heater and the radiator. It's a misconception that the high flow pump can force "too much" coolant through the heater and "not enough" through the radiator. Increasing the fluid pressure will increase the flow rate through both restrictions at least a little bit. It's possible if the heater is wide open and the radiator is highly restrictive (seems like that would be poor auto design) that the majority of the increase in pressure is going to the heater, but there will always be at least a marginal increase in flow though the radiator due to the increased pressure over stock.

No matter what (stock or modded cooling system), increasing the restriction to the heater core will increase the flow through the radiator. I'm not saying this is a solution we should all implement. But if you have a problem somewhere else in the system and are overheating then cutting the flow to the heater will be a band-aid fix to increase the flow to the radiator.

I guess, I'm not buying your jump to saying that high flow parts are forcing "too much" fluid through the heater. High flow/pressure will increase the flow to everything, including the heater and the radiator.
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