[EvanM87]

I have a 67 Mustang coupe that has had a 351w swap done to it. I was driving it around in about 80 degree heat and noticed my temp gauge was climbing to "overheating" Levels. I started to troubleshoot the issue. I made sure my coolant levels were good then I started to water down the coolant to see if that would help. Next I flushed the radiator in hopes that it was just clogged. I replaced the thermostat, and my water pump (which had a slight whine to it) None of this fixed the issue. I took her on a short drive to continue to troubleshoot and my gauge climbed quickly so I swapped out my temp sender, now it climbs even more quickly. I had her out for a matter of about 10 minutes before my gauge was maxed out. I popped the hood and the engine was barely warm. I now am wondering if the coil in the gauge is shot. I spent sometime online looking at how to replace my gauge but couldn't find any good videos. Does anyone have anything for me before I start just trying to figure it out myself?

Thanks in advance.

 

[07redstang]

First you need to establish the exact temperature the engine is running both at extended idle and on the road at speed. Harbor freight has cheap mechanical gauges you can use to do that.

 

[EvanM87]

First you need to establish the exact temperature the engine is running both at extended idle and on the road at speed. Harbor freight has cheap mechanical gauges you can use to do that.

Are these what you are talking about?

Harbor Freight Tools – Quality Tools at Discount Prices Since 1977

Harbor Freight buys their top quality tools from the same factories that supply our competitors. We cut out the middleman and pass the savings to you!

www.harborfreight.com

 

[Yadkin]

You should buy an infrared thermometer and measure the temperature at the thermostat casting. Normal operating temperature is 180-200F.

It sounds like you have a problem with the temperature sender. Fuel, coolant temperature and oil pressure gauges all work exactly the same. There is a CVR (constant voltage regulator) supplying 6 volts to all three gage circuits. Each sender is a variable resistor; for temperature the resistance goes down as the temperature increases. That heats up the dash mounted gauge, which works like a thermometer.

Since only one of the gages is abnormal the CVR is working properly. Since the gage needle sweeps through its range it is working properly. That leaves the temperature sender. Buy a good one- avoid Chinese made parts.

 

[EvanM87]

You should buy an infrared thermometer and measure the temperature at the thermostat casting. Normal operating temperature is 180-200F.

It sounds like you have a problem with the temperature sender. Fuel, coolant temperature and oil pressure gauges all work exactly the same. There is a CVR (constant voltage regulator) supplying 6 volts to all three gage circuits. Each sender is a variable resistor; for temperature the resistance goes down as the temperature increases. That heats up the dash mounted gauge, which works like a thermometer.

Since only one of the gages is abnormal the CVR is working properly. Since the gage needle sweeps through its range it is working properly. That leaves the temperature sender. Buy a good one- avoid Chinese made parts.

I bought a new sender from Napa last week. That was the latest in my troubleshooting. It increased the swings in my gauges. I do have a infrared thermometer though so I'll try that out first. Thanks for the advice.

Side note, I do also notice that my oil pressure gauge has some wild swings too. When the car first starts the oil pressure is redlined as it heats up the pressure decreases but there is visible movement on the pressure gauge when I hit the accelerator. Not sure if this is normal function or not as I am still learning about this vehicle.

 

[Yadkin]

I bought a new sender from Napa last week. That was the latest in my troubleshooting. It increased the swings in my gauges. I do have a infrared thermometer though so I'll try that out first. Thanks for the advice.

Side note, I do also notice that my oil pressure gauge has some wild swings too. When the car first starts the oil pressure is redlined as it heats up the pressure decreases but there is visible movement on the pressure gauge when I hit the accelerator. Not sure if this is normal function or not as I am still learning about this vehicle.

Oil pressure should be high when the engine is cold because the oil is more viscous. As the oil heats up the pressure should go down. Proper oil temperature under operation is 212F, plus or minus twenty degrees. Oil pressure should go up with RPMs.

 

[EvanM87]

Oil pressure should be high when the engine is cold because the oil is more viscous. As the oil heats up the pressure should go down. Proper oil temperature under operation is 212F, plus or minus twenty degrees. Oil pressure should go up with RPMs.

Ok. I figured but thought I would note it.

I just got back from a 10 minute drive doing about 35 mph the whole time and only sitting at 1 stop light. Using the infrared thermometer. I was getting readings of about 189-206 degrees from the area around the sender and the top of my radiator was 211F. I think my radiator might be shot because the half with the intake/output was in the high 100's to low 200's but the opposite side was in the 90's. I know there is a flaw in the design of the radiator and it only uses the right half for most of it's cooling but that's a large swing. I would assume next step is to replace the radiator if I have already flushed it?

 

[Yadkin]

90F on one side says that side is clogged. You said that you flushed the radiator. If you used a quick flush method that usually doesn't get the majority of crud out. Use a long term flush (200 miles over up to a week), followed by multiple rise cycles until the water gets clear. Then refill with 50-50 antifreeze and distilled water.

 

[EvanM87]

90F on one side says that side is clogged. You said that you flushed the radiator. If you used a quick flush method that usually doesn't get the majority of crud out. Use a long term flush (200 miles over up to a week), followed by multiple rise cycles until the water gets clear. Then refill with 50-50 antifreeze and distilled water.

I think I am down to having to replace the radiator. I used the "super flush" method. Unfortunately, the car over heats too quickly to run it with the chemicals for too long but I ran the car until it started to reach 200 degrees. I let the chemicals sit in the radiator for the "longest recommended time" of 4 hours. Here was my process:
1) Drain the existing fluid.
2) Ran water through radiator with plug open, car off just to try and get what I could out. (Noticed the drain plug has a very low flow even with fill cap off)
3) Closed drain. Dropped my radiator flushing, cleaning fluid in the radiator, topped the rest off with water. Ran the car until it was getting too hot.
4) Let it sit for 4 hours.
5) Drained the radiator and flushed with water. Plug still had very low flow
6) Topped radiator back off with water and ran the car to flush the engine/heater core. Drained that fluid. At this point, fluid is still very brown and still has green in it too. So i popped the lower hose and clear water came gushing out.
7) Repeated steps 3-6 again. Still have green brown fluid, plug flow is still very low.
8) Ran water through the system 5 times, draining it each time and my fluid is still a greenish, brown color.

 

[07redstang]

200* is not too hot

 

[EvanM87]

200* is not too hot

200 was where I cut it off at. If I let it idol it will keep going up and up. While I was out test driving the engine was putting off so much heat that i could feel it through my firewall.

 

[Yadkin]

I think I am down to having to replace the radiator. I used the "super flush" method. Unfortunately, the car over heats too quickly to run it with the chemicals for too long but I ran the car until it started to reach 200 degrees. I let the chemicals sit in the radiator for the "longest recommended time" of 4 hours. Here was my process:
1) Drain the existing fluid.
2) Ran water through radiator with plug open, car off just to try and get what I could out. (Noticed the drain plug has a very low flow even with fill cap off)
3) Closed drain. Dropped my radiator flushing, cleaning fluid in the radiator, topped the rest off with water. Ran the car until it was getting too hot.
4) Let it sit for 4 hours.
5) Drained the radiator and flushed with water. Plug still had very low flow
6) Topped radiator back off with water and ran the car to flush the engine/heater core. Drained that fluid. At this point, fluid is still very brown and still has green in it too. So i popped the lower hose and clear water came gushing out.
7) Repeated steps 3-6 again. Still have green brown fluid, plug flow is still very low.
8) Ran water through the system 5 times, draining it each time and my fluid is still a greenish, brown color.

Since it's still brown (rust) your engine block is also dirty. Since it's green you aren't doing a complete flush. There are several you tube videos on how to do this properly. Start by going to your local parts store and buying a flush chemical that works over several days an at lest 100 miles.

Don't bother draining out of the petcock. That is probably plugged as well. Just remove the lower hose.

 

[EvanM87]

Since it's still brown (rust) your engine block is also dirty. Since it's green you aren't doing a complete flush. There are several you tube videos on how to do this properly. Start by going to your local parts store and buying a flush chemical that works over several days an at lest 100 miles.

Don't bother draining out of the petcock. That is probably plugged as well. Just remove the lower hose.

Yep followed a youtuber on their complete flush protocol. That's why I listed out my steps. My guess is that the radiator is so blocked that liquid is trapped on the one half and just trickles out because if I pull my hoses the liquid is pure water or bright green. If I drain through the radiator plug it takes a long time to trickle out unless under pressure and when it does its the only place I am getting any discoloration. I am going to try some more chemicals today but I am not hopeful. I found out from the guy I bought it off of a few years back, that he had let the car sit in a heated garage for 20 years without draining the radiator. My guess is that the coolant probably ravaged the inside of that radiator.

Does anyone have a cleaner they would suggest? Would CLR be better? I assume there is no way to easily pull the core out of the radiator without destroying the housing or needing to weld right?

 

[Yadkin]

Yep followed a youtuber on their complete flush protocol. That's why I listed out my steps. My guess is that the radiator is so blocked that liquid is trapped on the one half and just trickles out because if I pull my hoses the liquid is pure water or bright green. If I drain through the radiator plug it takes a long time to trickle out unless under pressure and when it does its the only place I am getting any discoloration. I am going to try some more chemicals today but I am not hopeful. I found out from the guy I bought it off of a few years back, that he had let the car sit in a heated garage for 20 years without draining the radiator. My guess is that the coolant probably ravaged the inside of that radiator.

Does anyone have a cleaner they would suggest? Would CLR be better? I assume there is no way to easily pull the core out of the radiator without destroying the housing or needing to weld right?

Is the radiator adequate for the job? Some of them were too small to begin with and upgrades would just make that worse. If it is adequate then a professional shop can do a chemical cleaning or just replace the entire core. Of course it may be cheaper to get a new, larger radiator.

Either way you have to get the rust out of the block. I would try to do that with the old radiator, otherwise you risk clogging up a new one. Prestone used to make a reverse flush kit that you'd connect a garden hose and run water under pressure backwards through the system. You'll need to remove the thermostat and heater valve to do that. Otherwise it's a fairly simple process.

After a reverse flush do another chemical flush through several heat cycles.

Keep hammering away at this systematically and you will eventually win the battle.

 

[EvanM87]

Is the radiator adequate for the job? Some of them were too small to begin with and upgrades would just make that worse. If it is adequate then a professional shop can do a chemical cleaning or just replace the entire core. Of course it may be cheaper to get a new, larger radiator.

Either way you have to get the rust out of the block. I would try to do that with the old radiator, otherwise you risk clogging up a new one. Prestone used to make a reverse flush kit that you'd connect a garden hose and run water under pressure backwards through the system. You'll need to remove the thermostat and heater valve to do that. Otherwise it's a fairly simple process.

After a reverse flush do another chemical flush through several heat cycles.

Keep hammering away at this systematically and you will eventually win the battle.

Thanks Yadkin,

I'll take a look for the reverse flush. I know that they did an engine swap from a 289 to a 351 and they put a more aggressive cam in her. The original radiator is supposed to support a 351w. With the aggressive Cam I am not sure if the lower RPM's mixed with higher amounts of gas would offset each other but overheating wasn't a huge issue until recently and it is over heating faster and faster so that's why I feel like it's inside the radiator rather than the radiator itself.

 

[EvanM87]

Thanks Yadkin,

I'll take a look for the reverse flush. I know that they did an engine swap from a 289 to a 351 and they put a more aggressive cam in her. The original radiator is supposed to support a 351w. With the aggressive Cam I am not sure if the lower RPM's mixed with higher amounts of gas would offset each other but overheating wasn't a huge issue until recently and it is over heating faster and faster so that's why I feel like it's inside the radiator rather than the radiator itself.

UPDATE:
After flushing the entire system multiple times trying to unclog the radiator and contacting several machine shops and mechanics, I ended up replacing with a new fomoco 3 channel radiator. I've been driving it around and my temp gauge continues to show its running hot. I pull my infrared thermometer and measure the block temp and find I'm between 160 and 185 so I would say that I now need to replace the temp gauge but the car is operating at normal temp.

 

[Grimbrand]

"new" temp senders are 100% garbage.

Even expensive ones. You cannot find an electric temp sender that's worth a darn. However, you can probably get a used original that'll work just fine; get in touch with West Coast Classic Cougars, or hit a salvage yard and find any old Ford. Same holds true of the oil pressure senders. The companies that used to make them have all closed, and now they're all being made in China by cut-rate shops that don't care if they're good parts. If yours displays anything at all, it will be almost completely random on the gauge, and definitely not linear.

This is not a dig at China; just how it happened. We supported the 'cheapest' companies, and all the rest went out of business.

 

[EvanM87]

"new" temp senders are 100% garbage.

Even expensive ones. You cannot find an electric temp sender that's worth a darn. However, you can probably get a used original that'll work just fine; get in touch with West Coast Classic Cougars, or hit a salvage yard and find any old Ford. Same holds true of the oil pressure senders. The companies that used to make them have all closed, and now they're all being made in China by cut-rate shops that don't care if they're good parts. If yours displays anything at all, it will be almost completely random on the gauge, and definitely not linear.

This is not a dig at China; just how it happened. We supported the 'cheapest' companies, and all the rest went out of business.

Good to know. I keep all my parts I pull off her. I'll put the original back on and see how that works. Thanks for the info, and that's a darn shame.