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08-09-2016, 11:18 AM | #1 |
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Intermittent Overheating at Highway Speeds
On long drives, I have recently experienced an intermittent overheating problem that I can't find a good physical explanation for.
My pickup normally runs comfortably cool as indicated on the MotoMeter, maybe 1/2 inch below the black line. However, after about an hour of highway driving (even on level ground), the temperature begins to climb and after about 5 minutes the temperature climbs to about the top of the MotoMeter. If I pull off for 5 minutes, when I restart the car and get back on the road the temperature on the MotoMeter quickly falls back to normal, and stays there for about another hour. If I pull off onto a slower road (25-35 MPH), the temperature quickly falls back to normal. This weekend, I even pulled off into stop and go traffic in town and the temperature fell back to the normal range! I didn't touch the spark lever as traffic slowed either, so it can't be that. Someone suggested maybe there is some crud in the cooling system that is occasionally lodging in a bad place, and getting dislodged with the speed change? Can anyone else come up with a good explanation of what is going on?
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08-09-2016, 11:24 AM | #2 |
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Re: Intermittent Overheating at Highway Speeds
Test the actual temp when it's reading high with a thermometer... The motor meter is an inaccurate gauge mostly for looks or a half ass guide..
Last edited by Mitch//pa; 08-09-2016 at 12:02 PM. |
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08-09-2016, 11:36 AM | #3 |
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Re: Intermittent Overheating at Highway Speeds
Do you have a thermostat installed? Could be your motometer. When the engine is shut down the temp should go up not down. With the water no longer being circulated the heat collects in the high point of the radiator and should send the temp up.
Next time it does this feel the radiator, is it really hot or does it feel normal? Do you have any out flow at the tube? If it was getting that hot you should have boil over. Is it foaming? I have found with my Model T, some water pump grease has caused a bit of foaming and if that foam touches the motormeter causes the temp to go up on it. Motometers read the air temp above the water not the actual water temp. |
08-09-2016, 11:50 AM | #4 |
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Re: Intermittent Overheating at Highway Speeds
Replies in Bold.
Do you have a thermostat installed? No. Could be your motometer. When the engine is shut down the temp should go up not down. With the water no longer being circulated the heat collects in the high point of the radiator and should send the temp up. Yes, the temperature on the MotoMeter does climb when you stop. It quickly falls back into the normal range when you're back on the road after the stop. Next time it does this feel the radiator, is it really hot or does it feel normal? I just got back from a 350 mile trip, I'll try this out when I'm ready to cram myself back in the cab for an hour. Do you have any out flow at the tube? If it was getting that hot you should have boil over. Yes. Is it foaming? I have found with my Model T, some water pump grease has caused a bit of foaming and if that foam touches the motormeter causes the temp to go up on it. That is plausible. I have noticed that sometimes on inclines the temperature will spike & then quickly decline, and I was wondering if it was because the water was temporarily touching the MotoMeter itself. Motometers read the air temp above the water not the actual water temp. Yep. Out of curiosity, does anyone know what the air temperature itself is in the normal range when the water is normal operating temp?
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08-09-2016, 12:35 PM | #5 |
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Re: Intermittent Overheating at Highway Speeds
first steps to take when there is an overheat issue:
1. use a temp gun or actual temp gauge to assess what you really have, as Mitch states, motometers are notoriously innaccurate 2. be absolutely certain timing is correct and that you are running the spark rod in the correct place "does anyone know what the air temperature itself is in the normal range when the water is normal operating temp?" I doubt this info is known by anyone. get an IR temp gun; it is worth its weight in gold BTW your temp differential from top to bottom of a good radiator s/b 30° You said this is a recent problem. What is the back story? what was most recently done to the car before this began
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08-09-2016, 12:57 PM | #6 |
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Re: Intermittent Overheating at Highway Speeds
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Grab one of these for now: http://www.harborfreight.com/hand-to...ing-69465.html Old movie of mine: (before I installed a 160F thermostat ) https://www.youtube.com/watch?v=LgUi5yzdO3c
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08-09-2016, 03:24 PM | #7 |
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Re: Intermittent Overheating at Highway Speeds
warn impeller in your water pump..............?
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08-09-2016, 03:26 PM | #8 |
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Re: Intermittent Overheating at Highway Speeds
Haven't I read somewhere about some waterpumps pumping to much, to fast?
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08-09-2016, 03:31 PM | #9 |
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Re: Intermittent Overheating at Highway Speeds
After my vinegar treatment a few years ago I removed the radiator, turned it upside down and back flushed it with a sump pump in a large tub of water. I then used the same sump pump to back flush the block. I got a lot of rust flakes out, and installed a screen in the top hose to make sure I trapped any more junk before it could block off radiator tubes.
Unfortunately many of these old engines have lots of rust from people thinking plain water is a good idea. |
08-09-2016, 03:40 PM | #10 |
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Re: Intermittent Overheating at Highway Speeds
I too had the same problems when I got my coupe in 1985. Club took a tour to Daytona Beach. Up US 75,. about a 450 mile round trip. Cured it by getting rid of the motometer. Never had a problem since. My blood pressure went up with the motometer went up and went down when the meter went down . Never added any water during the whole ordeal.Tony
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08-09-2016, 06:16 PM | #11 | |
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Re: Intermittent Overheating at Highway Speeds
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08-10-2016, 05:45 AM | #12 |
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Re: Intermittent Overheating at Highway Speeds
"Can anyone else come up with a good explanation of what is going on? "
Don't over think the problem. With the engine running, what reduces coolant temperature? Radiator. As Tom mentioned, I think you will find a thorough flushing will cure your overheating. But first verify you don't have late timing as Tbird suggested.
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08-10-2016, 06:17 AM | #13 |
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Re: Intermittent Overheating at Highway Speeds
Check the torque on your head bolts.
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08-10-2016, 06:39 AM | #14 |
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Re: Intermittent Overheating at Highway Speeds
As I mentioned earlier before jumping in the pond confirm that its running hotter than it should be using an accurate manual check...
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08-10-2016, 10:08 AM | #15 |
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Re: Intermittent Overheating at Highway Speeds
With a really good Boyce Motor meter, Minervas' temp would go UP & DOWN on regular cycles. She was LOW on water! A ROOFING nail in the overflow fixed it. (TIP# 11)
Bill W.
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08-10-2016, 09:46 PM | #16 |
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Re: Intermittent Overheating at Highway Speeds
I had a problem with my four door I had a original rad that leaked and had repairs on it so i replaced it and water pump and i was still having issues till i found out that the overflow tube go plugged up by some fuze from and old gasket that had gone bad and ended up in the system blew out over flow tube and thing runs cool as a cucumber now
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08-10-2016, 10:19 PM | #17 |
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Re: Intermittent Overheating at Highway Speeds
Ian,
Go out and buy a cheap dial meat thermometer. (or borrow one from the kitchen) Pull the radiator cap and see what the temperature actually is. Your shooting in the dark until then. This is one tool I think all A and AA owners should have in their tool kit.
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08-11-2016, 06:58 AM | #18 |
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Re: Intermittent Overheating at Highway Speeds
meat thermoter. This is the tool crosscut is referring to. Bought it at Walmart. takes about half minute to reach running temp in dial. ken
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08-11-2016, 08:32 AM | #19 |
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Re: Intermittent Overheating at Highway Speeds
I installed a 160 deg thermostat and temperature gauge yesterday (from Snyder's). Fired her up and no leaks after idling for about 15 minutes so went for a test ride. It's 94 deg today. The APCO gauge was at 180 when I started down the street. I went about 15 miles round trip with a few stretches to 55 mph(Mitchell OD). Mostly 45 to 50 though. The gauge climbed to 190 and stayed there. I didn't lose any water. Question is, does this seem reasonable? I have searched but not found what normal should be. Does 190 under load sounds reasonable?
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08-11-2016, 08:42 AM | #20 |
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Re: Intermittent Overheating at Highway Speeds
Gud mawnin VFR. I don't know what norml should be. Outside temperature will have some bearing on that. "lecoupe, the one picturesd in my avatar above will cruise at 45 to 55 (4th gear overdrive) and temp will be consistently at 175 to 180. That is in 94 - 98 degree Texas heat. On an 80 to 90 degree day she will crusie at about 165 degrees.
Cruising at 190 is risky. That only gives you 20 degrees of margin until boil. Maybe 25 degrees if you have 50/50 antifreeze. Compare the APCO temp gauge to the meat thermometer pictures above. Sometimes I wonder how accurate some of th Temp gauges are. |
08-11-2016, 08:56 AM | #21 | |
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Re: Intermittent Overheating at Highway Speeds
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08-11-2016, 09:05 AM | #22 |
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Re: Intermittent Overheating at Highway Speeds
I purchased the same gauge and just installed it. Mine also reads nearly 190 degrees. I have a Motometer, and checked my new radiator with one of those IR heat sensing guns. The top tank was about 165 with the Motormeter showing about 1/4 inch of red. My new gauge is reading about 190 with the same level on the Motormeter. I suspect the gauge is reading high, but haven't checked it again.
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08-11-2016, 09:34 AM | #23 |
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Re: Intermittent Overheating at Highway Speeds
Ken, I was expecting to see the APCO in the middle of the green. It never smells hot or loses any water. Will check with my Thermapen before starting in on the radiator. I need to make sure things are good before installing a counterbalanced engine I'm working on.
Thanks for the reply, Hugh |
08-11-2016, 10:32 AM | #24 |
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Re: Intermittent Overheating at Highway Speeds
Well it not the APCO. On to the radiator!!
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08-31-2016, 10:47 AM | #25 |
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Re: Intermittent Overheating at Highway Speeds
Follow up:
Pulled the radiator and took it to the only radiator shop in town. The owner (Randy) told me when I called he doubted it would need rodding out because the tubes are big in a model A. This shop has been in business a long time. Randy has a rig to really put some flow through. After a couple of back flush cycles it was flowing great. It was just rust flakes laying on the top of the tubes. I also took a radiator that was on a chassis I bought. This rad is considerably heavier with larger tubes. Randy said it looks like an original to him. It also flowed great. The whole thing probably took 30 minutes. Randy wouldn't take any money. This morning I compared the two radiators by running them back to back. The lighter radiator has more smaller tubes & held 165 deg. The heavy radiator ran a little hotter on my APCO gauge maybe 170. My test route included about 5 miles at 55 in overdrive. This is a totally stock engine. My project engine has a 6 to 1 head and IB330 cam. Logic says it will generate more heat so I'm thinking of staying with the lighted radiator. Photo is what I'm calling 170. |
08-31-2016, 06:15 PM | #26 |
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Re: Intermittent Overheating at Highway Speeds
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http://www.thermomart.com/engine-wat...n-Alarm-Sensor I know the digital display doesn't look right in a Model A so I intend hiding it, leaving the Apco visible BUT the audible warning will still be activated if the temp reaches 190 deg. These gauges don't rely on the water to give an accurate reading. I'm sure if I had one of these when I cracked the block on that engine, I would have saved myself $$$$$$$$$$$
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08-31-2016, 06:40 PM | #27 |
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Re: Intermittent Overheating at Highway Speeds
I think you will find reply #13 by JacksonIII is on the right track! The head gasket is allowing hot gasses to bypass the gasket and heat the water. It only happens when you ask the engine to work a little harder than normal. Harder like go a little faster. You can buy a kit to test for combustion gases in the coolant or just have a friend watch in the radiator while you put a strain on the engine. Rainmaker Ron
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08-31-2016, 09:28 PM | #28 |
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Re: Intermittent Overheating at Highway Speeds
Ian... Curious if you have made any progress on finding out what is going on?
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09-01-2016, 10:47 AM | #29 |
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Re: Intermittent Overheating at Highway Speeds
No, I haven't had much time for Model As recently. I hope to drive over the mountains to the other side of Washington later in September, so I'll have a chance to check the temp while running then.
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09-01-2016, 05:29 PM | #30 |
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Re: Intermittent Overheating at Highway Speeds
I had a similar thing with my car. The GAV would slowly close itself on a long drive.
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09-01-2016, 11:42 PM | #31 | |
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Re: Intermittent Overheating at Highway Speeds
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09-08-2016, 07:50 PM | #32 | |
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Re: Intermittent Overheating at Highway Speeds
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Where are these kits available, and what are they called? |
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09-08-2016, 08:38 PM | #33 |
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Re: Intermittent Overheating at Highway Speeds
OK, I'm going to hi jack this thread at least for a moment. I ruined an engine recently when the temp went through the roof within a few hundred metres. The problem with an ordinary gauge is that it doesn't let you know what is going on unless you happen to look at it at just the right time. I figure an audible alarm is what I need.
Because I don't like the look of these in a Model A, I intend hiding it but the buzzer will still be a savoir. Has anybody any experience with these? http://www.thermomart.com/engine-wat...n-Alarm-Sensor I can't get a reply to an enquiry through their web site and I can't ring them - maybe something to do with being in another country from them. They are in Canada In the case of my ruined engine, a so called leakless water pump decided it was not going to stay leakless. As a result, on a medium length trip, the coolant level dropped till the water pump impeller was just dipping the coolant and spraying the sensor in the water neck so the gauge got a reading but there was not enough to circulate through the radiator and the rest is history (like the motor). The devices in the link above don't rely on the coolant for a reading and respond very quickly to a change. The owner can set a temperature at which the buzzer will sound a warning so overheating will not be an issue. If there is a barner out there who is prepared to help me in this, I would very much appreciate it.
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09-09-2016, 02:45 AM | #34 |
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Re: Intermittent Overheating at Highway Speeds
They are called Combustion Leak Detectors.
Most auto parts stores that loan/rent tools have them if you choose not to purchase your own.
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09-09-2016, 02:57 AM | #35 |
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Re: Intermittent Overheating at Highway Speeds
Synchro, not sure if this would interest you but there is a less expensive version on EBay
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