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Old 07-31-2023, 04:43 PM   #1
jemccab
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Default Water temp problem

I have a water temp problem.Water temp is checked at the head outlet. Checked timing 2 times, GAV is at 1/2 to 3/4 open, Cleaned radiator with 3 gal of vinegar over night and back flushed radiator and block. Flow checked radiator from full to empty in 4-5 sec.

Question I have is what water temps should I see with a infared gun at the upper radiator hose and lower radiator hose.
I am seeing 180 deg+- 10deg at top 140 deg +-5deg bottom after 20 min drive.

I see members saying get a infared gun but no real numbers to look to strive to.
Thanks
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Old 07-31-2023, 04:56 PM   #2
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Default Re: Water temp problem

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Originally Posted by jemccab View Post
I have a water temp problem.Water temp is checked at the head outlet. Checked timing 2 times, GAV is at 1/2 to 3/4 open, Cleaned radiator with 3 gal of vinegar over night and back flushed radiator and block. Flow checked radiator from full to empty in 4-5 sec.

Question I have is what water temps should I see with a infared gun at the upper radiator hose and lower radiator hose.
I am seeing 180 deg+- 10deg at top 140 deg +-5deg bottom after 20 min drive.

I see members saying get a infared gun but no real numbers to look to strive to.
Thanks
That is an often quoted test but in reality, it means nothing.
Is your ignition timing correct? A retarded timing will cause the engine to run hot.
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Old 07-31-2023, 05:02 PM   #3
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Default Re: Water temp problem

I have not checked with a gun lately but the temperature read by my gauge leaving the top of the engine is 175-180°F.
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Old 07-31-2023, 05:11 PM   #4
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Default Re: Water temp problem

Describe your "water temp problems". At those temps you should not be boiling. Are you losing coolant out the overflow? Is cap leaking? Radiator cap should be gasketed so it doesn't leak. Fill radiator just over the tubes, overfilling will result in blowing out excess. Drop a roofing nail in the overflow tube(Bill W trick).
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Old 07-31-2023, 11:50 PM   #5
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Default Re: Water temp problem

See attached.

Readings on the cast iron neck will be more representative of the coolant temperature than reading on rubber.

If it's not boiling, it's OK.

If you have set your initial timing to TDC, per Ford's directions, don't move your spark advance lever down more than ~3/4 down. That's 30 degrees of advance, which is plenty until you hit about 45 MPH.
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File Type: pdf Infrared Thermometer Guns.pdf (147.9 KB, 57 views)
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Old 08-01-2023, 09:51 AM   #6
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Thanks Jim. That is what I've been doing. Its not boiling just running warmer than I would like per the temp gauge at the top of the head. I'll check the gauge for accuracy next. Great information.
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Old 08-01-2023, 10:06 AM   #7
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Default Re: Water temp problem

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I am seeing 180 deg+- 10 deg at top 140 deg +-5 deg bottom after 20 min drive.
Sound about right. What's the O A T (outside air temperature)?
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Old 08-01-2023, 10:18 AM   #8
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Default Re: Water temp problem

You are running with the GAV open way too much! If the engine is running correctly, the GAV should be 1/8th to 1/4 turn open for normal running at operating temperature.
I have a temperature sensor in the upper radiator hose just below a 160F thermostat and the gauge normally registers steady at 160F while cruising. On an exceptionally hot day (100F), the operating temperature registers 180F.
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Old 08-01-2023, 10:37 AM   #9
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Default Re: Water temp problem

OAT upper 80s.
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Old 08-01-2023, 10:39 AM   #10
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Default Re: Water temp problem

Bob, I start at 3/4 open and as it warms up i go to about 1/2 open. Any less it gets to lean and looses power.
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Old 08-01-2023, 01:19 PM   #11
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Default Re: Water temp problem

Carburetors are all different so there is no set correct GAV setting. Set it where the engine runs best.

180 is about right. I would worry if it gets to 210 or starts to boil. The Model A has a combination water pump and thermosyphon system so the coolant has a greater flow rate at higher temperatures.
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Old 08-01-2023, 05:18 PM   #12
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Default Re: Water temp problem

jemccab,
I feel your pain...I'm wondering about the accuracy of my temp gauge too. I installed a new Rex-a-Co temp gauge a few months back and going down the road the gauge showed to be on the high side of the "Driving Range" segment of the gauge which is a range between 140* and 190*. Now, with all the HOT weather we're having here in north Texas (104*-108*) the temp gauge indicates water temp slightly above 190* but stays steady there. So far, no indication of boiling or water coming out the overflow. A couple of days ago, after getting it up to temperature I used a pocket temperature gauge with a probe that you can place into the filler neck of the radiator, and it only reached 170*. Since it's not boiling over I'm going to assume that things are OK, but I still don't know if I can trust the gauge installed in the car is reading correctly.
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Old 08-01-2023, 05:28 PM   #13
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Default Re: Water temp problem

have you flushed the block--not just the radiator. years of pouring in oats and who knows what can cause the block to plug
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Old 08-01-2023, 06:59 PM   #14
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Default Re: Water temp problem

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Thanks Jim. That is what I've been doing. Its not boiling just running warmer than I would like per the temp gauge at the top of the head. I'll check the gauge for accuracy next. Great information.
Before installing my Borg-Warner temp gauge, I placed the sender bulb in some boiling water on the stove and confirmed that the needle on the gauge went up to 212. Then I knew it was accurate.

There used to be a little calibration tick printed on the face of the gauges at the 212 point, but it looks like they quit doing that. Still, you can eyeball it pretty easily.

I don't know if there is a calibration point on the reproduction Rex-a-co gauges.
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Old 08-10-2023, 08:19 AM   #15
jemccab
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Default Re: Water temp problem

Update. temps continue to go up. Did a 18 mile drive today and as I drove into driveway it started to boil over. I'm thinking head gasket.
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Old 08-10-2023, 08:56 AM   #16
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Default Re: Water temp problem

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Update. temps continue to go up. Did a 18 mile drive today and as I drove into driveway it started to boil over. I'm thinking head gasket.
Why do you think it could be a head gasket problem?

What was the air temperature on your drive, how hard did you push your car? Are you sure it was boiling or was it just going out the overflow?

Do you have a thermostat?
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Old 08-10-2023, 09:24 AM   #17
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Default Re: Water temp problem

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Before installing my Borg-Warner temp gauge, I placed the sender bulb in some boiling water on the stove and confirmed that the needle on the gauge went up to 212. Then I knew it was accurate.
Water only boils at 212°F @ sea level so compensate for higher altitudes if needed.
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Old 08-10-2023, 09:38 AM   #18
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Default Re: Water temp problem

you mention vinegar overnight..........


I let my 5% vinegar sit in my rad and engine block for up to 6 weeks. Not sure if overnight does anything.
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Old 08-10-2023, 10:12 AM   #19
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Default Re: Water temp problem

A person can run the spark control with full advance as long as the drive is fairly flat terrain but it should be retarded a bit to pull up steep hills or when loaded heavy and pulling up modest grades. This will make for a better F/A burn and is one of the reasons for having adjustable spark control.

The GAV can be adjusted for best running while on the fly. This can be adjusted a bit on the rich side to aid in cooling as long as the engine is still running down the road well. The fuel economy may be a bit lower but it will generally run somewhat cooler.

If any compression gets past the head gasket and into the water jacket then it will start hot spots where the coolant will boil. The longer it boils there the hotter the coolant will get till the whole radiator is boiling over. Generally a leaky head gasket will show up with coolant leaking back the other way while the engine is dormant. This will eventually show up on the affected spark plug and through constant loss of coolant. Lower compression model A engines will take a while to start showing the signs of a degraded head gasket but it will get worse before it gets better.
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Old 08-10-2023, 10:55 AM   #20
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Default Re: Water temp problem

For what it’s worth: An engine builder told me he has measured radiators that flowed perfectly using the gravity drainage test, but were significantly clogged.
That’s genuine hearsay of an unsubstantiated claim, made by an unidentified so-called expert as quoted by some guy on the internet, who may actually be a bot, or Artificial Intelligence server. Though if you knew me, you’d hesitate before attributing “intelligence” to me, whether artificial or any other kind.
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