Chasing this cooling issue for months

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TrailBeast

TrailBeast

AKA Mopars4us on Youtube
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Or maybe should call it a "heating issue" I don't know anymore.
318, 8 blade impeller, new 26" radiator, new 17" S blade 2400 CFM electric fan set up as a puller, 195 thermostat.
Also mechanical temp guage, not electric.

I can drive around town at low speeds in stop and go traffic and the temp stays right where it should, 195-210.
It will slowly come up to 210 then the fan comes on and brings it back down to 195 in about 1 block. (Seems great so far)
BUT, if I get out on the highway at 55-75, within 1 mile the temp is down to 175.
It can be 90 outside and it drops the engine temp to 175 at highway speeds.
Also I have waterflow through the radiator at 175 degrees and that makes sence as to the symtom.

Question is why?
With a replacement thermostat because I thought the first new one might be bad, it still overcools.
How is it possible that 175 degree water is getting past a 195 thermostat?
I know for a fact that this is what's happening due to the fact that I have a tiny flat spot just off the throttle stop at anything under 190 degrees and when the guage starts dropping under 190 the flat spot is there.

I'll bow (In Public) to anyone that can school me on why.:prayer::D

Thanks
 
Wish I had a too cool problem. Does your water pump have a bypass??I, d be happy and tune it for cooler temps
 
One regular question is "how do you know the temperature sensor is correct?". You are thinking of this since you compare to your engine performance. I assume you are using the small factory sensor screwed into the front of the intake manifold (1/8 NPT thread). If so, I doubt that more external air flow around it would change the reading. I think those are a resistive thermometer (RTD) which is usually a spool of fine platinum wire (maybe something cheaper in automotive). If it was a thermocouple, there are many strange false readings possible from connectors and such, but I don't think they were ever used for coolant sensors. If you have some other after-market or home brewed sensor then air flow might affect it.

Assuming the sensor reads correctly, you might research the "bypass hose" and flow circuit from the water pump to the intake manifold. I assume it is named that because it bypasses the thermostat. Maybe there is supposed to be a flow restriction washer or such somewhere. I have never studied it.
 
To me i would be happy the way it is working, i would never trust one of those mech gauges they could be out 20 degrees who knows , did you try shooting it with an infored gun . all areas hoses rad , engine ect. I would just be glad that it is not overheating and throwing it out on the ground.
 
daredevil said:
Wish I had a too cool problem. Does your water pump have a bypass??I, d be happy and tune it for cooler temps
Click to expand...
Been there and done that, blocked them ALL completely and made zero difference. (Except it was pain to refill it with no way of letting the bubbles out of the system till the thermostat opens)
Running under temp increases engine wear up 400 percent, or I would just deal with it the way it is.




BillGrissom said:
One regular question is "how do you know the temperature sensor is correct?". You are thinking of this since you compare to your engine performance. I assume you are using the small factory sensor screwed into the front of the intake manifold (1/8 NPT thread). If so, I doubt that more external air flow around it would change the reading. I think those are a resistive thermometer (RTD) which is usually a spool of fine platinum wire (maybe something cheaper in automotive). If it was a thermocouple, there are many strange false readings possible from connectors and such, but I don't think they were ever used for coolant sensors. If you have some other after-market or home brewed sensor then air flow might affect it.

Assuming the sensor reads correctly, you might research the "bypass hose" and flow circuit from the water pump to the intake manifold. I assume it is named that because it bypasses the thermostat. Maybe there is supposed to be a flow restriction washer or such somewhere. I have never studied it.
Click to expand...

I know for a fact that this is what's happening since I have that tiny flat spot just off the throttle stop at anything under 190 degrees and when the guage starts dropping under 190 the flat spot is there.
It is the thermocouple mechanical type installed in the front of the manifold, and it did the same exact thing with the original electric sensor.
Same readings, same results with both types.

Now, how is it possible that coolant is getting circulated at 175 degrees with all that blocked off bypass and heater stuff? ???

Sorry, had to edit this answer.
Lets say just for kicks that the guage is wrong and it's actually running at 195 when the guage says 175.
So when the gauge says 210 what would the temp actually be?
230 right?
Theres no way.
This is what makes me pretty sure of what's happening as well as the flat spot being there.
 
Gotta go do work stuff, but will be back in the early afternoon.
 
We have had bad thermoststs bad right out of the box but since nothing changed when you put in a new one I would think that would rule that out.
Get an infrared therometer and see what readings it gives you. You can readings on hoses, thermostat, water pump and anywhere else you want. I have chased down a lot of problems with it.
 
I'd like a nice little louvre system like miniblinds that I could open or close from the drivers seat and I could make it, but I'm not really sure it'd be worth it time wise.
(speedo type cable run to the front with a worm gear setup on the end to open and close it, and a knob under the dash)

I'll probably just cover a third of the radiator during this time of year and let the electric fan run a bit more.

That whole thing about having full coolant flow in the radiator at 175 with a 195 thermostat just messes with me.

Oklacarcollecto said:
We have had bad thermoststs bad right out of the box but since nothing changed when you put in a new one I would think that would rule that out.
Get an infrared therometer and see what readings it gives you. You can readings on hoses, thermostat, water pump and anywhere else you want. I have chased down a lot of problems with it.
Click to expand...
 
Why did you put a new 26 inch rad in? A 19 or 22 would probably put your temp where you want it.
 
I drive between high desert and low regularly.
I leave my house and it's 45 degrees out and when I get where I'm going it could be 110 outside.
I said before that I wanted to drive this car through hell itself and not overheat.
Just another case of "be carefull what you wish for" it seems.

Why is that 195 thermostat passing coolant at 175?
Seems to always go back to that to me.


tekslk said:
Bigger isnt always better.
Click to expand...
 
I know very little about aftermarket gauges. does your temp gauge have a nitrogen filled copper tube and bulb that supplies the signal ? If so , is that tube insulated ?
i'm just imagining a tube routed high under the hood and/or passing through a oversized hole in the firewall. Ambient air flow at highway speeds could lower the nitrogen signal to the gauge.
 
I don't see anything wrong with 175. That's just a product of that badass radiator. What I see is, that it should be running 175 pretty much in any situation and here's my reasoning. If it runs 175 on the open road and heats up at idle, that's an indication that there's not the same airflow at idle. Besides that, I can tell you just from the footnote on the Summit site that 2400 CFM ain't enough. As a general rule of thumb, most V8 engines need around 3500-4500 CFM to stay cool at idle. So if it were mine, I would do one of two things. Either leave it alone or get a higher capacity fan. Remember that it's not just the maximum temp that the engine acheives. It is also how long it stays there.
 
But, what the gauge says isn't what concernes me.
It's what the overcooling causes that does.
I know for fact that it is running too cool on the hiway.
I have a thermostatic control on my cooling fan that coinsides with the gauge reading, so if I set the thermostat under the hood for the fan to come on at 210, it comes on when the gauge inside says 210 so I know that it is giving me a correct readout.

Like I asked and it always seems to come back to, Why is 175 degree coolant passing through a 195 stat?

The only thing I can think of is that the coolant flow/pressue is forcing it's way past the stat when the stat reaches 175.
This is the only reason I can think of.


RedFish said:
I know very little about aftermarket gauges. does your temp gauge have a nitrogen filled copper tube and bulb that supplies the signal ? If so , is that tube insulated ?
i'm just imagining a tube routed high under the hood and/or passing through a oversized hole in the firewall. Ambient air flow at highway speeds could lower the nitrogen signal to the gauge.
Click to expand...
 
TrailBeast said:
I drive between high desert and low regularly.
I leave my house and it's 45 degrees out and when I get where I'm going it could be 110 outside.
I said before that I wanted to drive this car through hell itself and not overheat.
Just another case of "be carefull what you wish for" it seems.

Why is that 195 thermostat passing coolant at 175?
Seems to always go back to that to me.
Click to expand...

I may simply be malfunctioning or mis marked.
 
Originally it had a 180 in it and it did the same thing.
Put a 190, same thing.
Put a 195, same thing.

The only thing the different stats did was up the low speed temps.
Out on the hiway, all of them ran at 175
Freakin annoying.


StrokerScamp said:
I may simply be malfunctioning or mis marked.
Click to expand...
 
well hears a thought its still running at 195 blow your tstat if your engin doesnt have the buypass hucked up it cant serculate to give the coolant in the bottem of the block a chance to cycle hence the 175 reading when you go down the road it shut till it gets warmed up at a stop light and opens hope this helps . and do you have your heater on .???
 
Temp sensor is in the intake manifold so it's sensing engine coolant temp in the block, not in the radiator or hoses.
Remember I said if it's below 190 I have the flat spot and as soon as the gauge shows the drop below 190 the flat spot is back.
Heater, on or off. or disconnected it makes no difference.

robert 68 cuda said:
well hears a thought its still running at 195 blow your tstat if your engin doesnt have the buypass hucked up it cant serculate to give the coolant in the bottem of the block a chance to cycle hence the 175 reading when you go down the road it shut till it gets warmed up at a stop light and opens hope this helps . and do you have your heater on .???
Click to expand...
 
Take the T-stat out. or just use your old one. fill a pan with water,put the t-stat in and heat it on your stove. have some way of messuring water temp. observe at what temp the t-stat opens then slowly cool the water and observe when the t-stat closes. there could be a 20deg diffrence between open temp and close temp. Let us know your findings.
 
mod5v said:
Take the T-stat out. or just use your old one. fill a pan with water,put the t-stat in and heat it on your stove. have some way of messuring water temp. observe at what temp the t-stat opens then slowly cool the water and observe when the t-stat closes. there could be a 20deg diffrence between open temp and close temp. Let us know your findings.
Click to expand...

Did that and it works like it should, but out of the car there is no pressure against it from the water pump and I'm starting to think that once it gets to 175 and also has the pump pushing against it coolant is forcing it open.



godfatherofchry said:
is it possible to get a picture of the rad and hoses in the car..Artie
Click to expand...

Sure, just give me a few.
Got 50,000 things going on all at once this morning.
 
The radiator core itself is about an inch wider than the opening for the radiator
 

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TrailBeast;
A 195* degree thermostat should maintain an average engine temp of 175* with a good cooling and air circulating system. Remember that it isn't like a light switch on/off. You have a bypass hose and most likely a bypass built into the T~stat as well. 195* is the full open temperature but that stat will partially open at 175* try one in a pan of water and watch it. That partially opened position with highway speed airflow should give you the 175* operating temp you are experiencing. It is this exact same reason that I used to recommend to my diesel customers to run a 203* t~stat to maintain a 190* engine temp. Since the 195* is the highest I know of for your car all you can do is install a system that blocks airflow through the radiator at speed. The louvers you mentioned with an electric motor controlled with the same type of thermostat as your fan should do the trick.
~Michael
 
If you have significant flow in the upper hose when the thermostat is closed, you have an issue with the thermostat bore / housing.

With the engine cold, pull the radiator cap, and take the speed up to 1500 to 2000 rpm. If you see coolant flowing, it is bypassing the thermostat.

Unless you have been installing the thermostats upside down, there is no way water pump pressure can push one open.

What can happen is a mismatch of parts, or a poorly machined manifold / water neck allowing significant coolant flow to bypass the thermostat.

Through the years, mopar went from a 2.500 OD thermostat to a smaller one. The water neck bolt spacing changed, but I would not bet that some aftermarket parts were made with a mix of the two dimension sets...

Really the only place to get water into the radiator from the engine is the thermostat. The bypass, heater, etc all work against any flow heading to the radiator.

Check to see if you have upper hose flow on a cold start.

B.
 
well the first thing I would do is get rid of the electric fan and go with a regular fan be it 6or7 blade with a fan shroud.your elect. fan is only cooling the spot that its in. this being the resin for it getting to 210 and then I would go with a 180 or 185 stat I think that would regulate you temp. better...I have never had any luck with using an elec. fan for the only source of cooling.and I think 180 is an ideal temp.for an older motor....this is my thut and its worked for me.........Artie
 
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