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Coolant does not flow with thermostat installed
#1
I have a 1971 Mach 1, 351c 2V motor. The car recently overheated, and was expelling coolant out of the over flow tube. I have had the car for two years, without any overheating problems prior to this.

I inspected the oil and it looks fine, and no moisture out of the tail pipes after warm up. I removed and inspected all of the spark plugs, to see if the had a washed out look. All looked find. Leading me to believe it is not a head gasket.

I first checked the thermostat, only to find the previous owner had removed the thermostat, as well as the water restrictor plate.

I have done the following.

Checked the quality of the oil and it looks fine.
No moisture from tail pipes after warm up.

Purchased and installed the water restrictor plate offered by west coast classic cougars, along with a 180 thermostat for a Windsor motor. (a non Cleveland thermostat is required with this restrictor plate)

Removed and replaced water pump. Verifying no play in shaft and no internal damage.

Had the radiator serviced.

New upper, lower, and heater hoses.

I have drilled a 1/16" hole into the thermostat, installed the thermostat while leaving the upper hose disconnected. I then added water until I could see water coming out of the thermostat housing. I did this to verify I did not have an air pocket at the thermostat.

I then connected the upper hose to the thermostat housing. I filled the upper hose with water before attaching it to the radiator. Again trying to eliminate any air pockets.

At this time, the car is overheating within five minutes of start up, at an idle. The factory gauge is in the middle of the operating temperature range. However, the engine begins to emit a knocking sound that I'm associating with over heating.

With the thermostat OUT, and the restrictor plate installed, I can see coolant flowing through the radiator. When I increase the rpm's the coolant flows even more.

With the thermostat INSTALLED, along with the restrictor plate, I see no coolant flow in the radiator, and I get the overheating as described above within a few minutes. The coolant drops several inches in the radiator, then rises and spills out of the radiator.

Any help is appreciated.






I filled the radiator last night, and checked it this morning while cold. The water level is within an inch or so from top of radiator.

Could anyone explain or help solve the problem of no water flow with the thermostat installed

thanks,
  Reply
#2
Test thermostat to see if it opens and when by putting it in a
pot of water on the stove and verify with a meat thermometer.

Paul
  Reply
#3
rocket366;276235 Wrote:Test thermostat to see if it opens and when by putting it in a
pot of water on the stove and verify with a meat thermometer.

Paul


I did bench test the thermostat with a heat gun to verify it opened and closed. I have not yet tried it in boiling water.
  Reply
#4
Is the restrictor plate some sort of custom made one and not like the original? Why did you not go with original style? I know they are hard to find but you can get them. I also drill the small hole in all thermostats to let the air out so no pocket that will do no harm.
Like Paul said test the thermostat to make sure it does work. If it is ok then do pressure check for blown head gasket.


When a man is in the woods and talks and no women are there is he still wrong??
Tongue
David
  Reply
#5
klinton994;276234 Wrote:I have a 1971 Mach 1, 351c 2V motor. The car recently overheated, and was expelling coolant out of the over flow tube. I have had the car for two years, without any overheating problems prior to this.

I inspected the oil and it looks fine, and no moisture out of the tail pipes after warm up. I removed and inspected all of the spark plugs, to see if the had a washed out look. All looked find. Leading me to believe it is not a head gasket.

I first checked the thermostat, only to find the previous owner had removed the thermostat, as well as the water restrictor plate.

I have done the following.

Checked the quality of the oil and it looks fine.
No moisture from tail pipes after warm up.

Purchased and installed the water restrictor plate offered by west coast classic cougars, along with a 180 thermostat for a Windsor motor. (a non Cleveland thermostat is required with this restrictor plate)

Removed and replaced water pump. Verifying no play in shaft and no internal damage.

Had the radiator serviced.

New upper, lower, and heater hoses.

I have drilled a 1/16" hole into the thermostat, installed the thermostat while leaving the upper hose disconnected. I then added water until I could see water coming out of the thermostat housing. I did this to verify I did not have an air pocket at the thermostat.

I then connected the upper hose to the thermostat housing. I filled the upper hose with water before attaching it to the radiator. Again trying to eliminate any air pockets.

Although it's not uncommon, it is not good to run an engine w/o a thermostat. The fact that the previous owner was running w/o one is bothersome. There may be some issue this was masking, such as a cracked head. Over the 2 years that you ran the car, did you have to add coolant?

The extra work to eliminate air pockets is, in my opinion, unnecessary. Even after all of that, I would have run the engine with the radiator cap off until coolant is seen flowing through the radiator core....at this time, top it off and replace the cap. There is a bit of a learning curve to modulating throttle as coolant level rises to prevent or minimize the mess caused by coolant overflowing from the filler neck.

klinton994;276234 Wrote:At this time, the car is overheating within five minutes of start up, at an idle. The factory gauge is in the middle of the operating temperature range. However, the engine begins to emit a knocking sound that I'm associating with over heating.

I can't say that I've ever associated a knocking sound with overheating. What makes you think the knocking is from overheat? If the cooling system is in good condition, you should be able to run the engine at a fast idle with the radiator cap off. If it's overheating this will definitely not be possible. The coolant temperature needs to be verified to be sure you're not chasing the wrong issue.

The knocking sound is troublesome...perhaps from detonation as the engine warms up?

klinton994;276234 Wrote:With the thermostat OUT, and the restrictor plate installed, I can see coolant flowing through the radiator. When I increase the rpm's the coolant flows even more.

This is normal. Behavior will be the same with thermostat installed AND after the thermostat is fully open.

klinton994;276234 Wrote:With the thermostat INSTALLED, along with the restrictor plate, I see no coolant flow in the radiator, and I get the overheating as described above within a few minutes. The coolant drops several inches in the radiator, then rises and spills out of the radiator.

Aside from this knocking noise, what you're describing is normal for an engine that is coming up to temperature. The rise and fall of coolant level is due to the thermostat opening and closing as engine comes up to temperature. It may take a few cycles of this before the thermostat fully opens, but once it does, you should see steady flow through the radiator.

klinton994;276234 Wrote:I filled the radiator last night, and checked it this morning while cold. The water level is within an inch or so from top of radiator.

Could anyone explain or help solve the problem of no water flow with the thermostat installed

thanks,

As previous poster said, test the thermostat.

Something caused the engine to all of a sudden expel coolant from the overflow and there's some strange knocking sound. Start by checking the radiator's "pressure cap". You can borrow a tester from the parts stores and it should also have an adapter to pressurize your cooling system. Once you verify the pressure cap is ok you need to pressurize the system and let it sit with the plugs removed for a half an hour. After sitting under pressure, crank the engine and watch for signs of coolant expelling from the spark plug holes. This will tell you if you have a leak allowing coolant to reach a cylinder.

The knocking may be associated with excessive ignition advance....possibly due to one of the thermal switches. Disconnect and plug the vacuum hoses going to the distributor to eliminate this as a possible cause....also verify base timing is set properly.
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#6
Bench test the thermostat again. While it is still open try placing it in the block. You will have to do this pretty quick. You are looking to see if it falls into place or if the thermostat is hitting your block off plate.

I apologize for going back to the basics. Are you sure you didn't have a restrictor plate? Are you sure you installed the block off plate correctly? I have never attempted to install or remove the restrictor plate so I don't know how easy it would be to install incorrectly.

'Mike'
73 Convertible - 351C/4V CC heads/4bolt/forged flat tops/comp 270/rhodes/mallory unilite/tri-power/hookers/glasspacks/c6/3.50 limited slip/Gear Vendors/Global West sub frames, strut rods and shelby style traction bars/ Rear sway bar/tilt steering (not original)

Pics of modifications included in:
  Reply
#7
Interesting problem. Definitely test or replace your cap, even with new hoses if your radiator does not pressurize the lower hose can collapse. Most do not come with the spring in the lower hose, anymore. If the inner layer of the lower hose separates it can also restrict the flow.

This was the only thing I could think of that hadn't already been covered.

I agree with David's question about the restrictor plate. I know that some of the Pantera guys came up with it and swear by it but I believe the original style restrictor plate and Cleveland specific thermostat are the best way for all-around cooling performance.
http://www.7173mustangs.com/thread-351c-cooling-system



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
  Reply
#8
rocket366;276235 Wrote:Test thermostat to see if it opens and when by putting it in a
pot of water on the stove and verify with a meat thermometer.

Paul

I tested the thermostat in water with a thermometer. My 180 deg. thermostat was open at 160 deg. based on the thermometer.
  Reply
#9
will e;276243 Wrote:Bench test the thermostat again. While it is still open try placing it in the block. You will have to do this pretty quick. You are looking to see if it falls into place or if the thermostat is hitting your block off plate.

I apologize for going back to the basics. Are you sure you didn't have a restrictor plate? Are you sure you installed the block off plate correctly? I have never attempted to install or remove the restrictor plate so I don't know how easy it would be to install incorrectly.

I took the thermostat, still in the pot of hot water, out to the car and placed it into the block. It fell right into place. The block of plate I installed fit right into a casting within the block, with no effort. At tapped it in with a socket.
  Reply
#10
Don C;276244 Wrote:Interesting problem. Definitely test or replace your cap, even with new hoses if your radiator does not pressurize the lower hose can collapse. Most do not come with the spring in the lower hose, anymore. If the inner layer of the lower hose separates it can also restrict the flow.

This was the only thing I could think of that hadn't already been covered.

I agree with David's question about the restrictor plate. I know that some of the Pantera guys came up with it and swear by it but I believe the original style restrictor plate and Cleveland specific thermostat are the best way for all-around cooling performance.
http://www.7173mustangs.com/thread-351c-cooling-system

I'm not an experienced gear head, but after viewing the illustration of the 351c cooling system I'm beginning to wonder about this after market restriction plate. I know some swear buy it. Help me to understand this correctly.

The stock restriction plate, has a fairly large orifice that I assume allows water to circulate throughout the orifice, the heads and block, via the by pass. Upon the engine reaching operating temperature, the thermostat does two things. It expands and blocks the orifice in the restriction plate, and at the same time opens at the top of the thermostat to allow the water to begin circulating through the radiator.

With the aftermarket restriction plate, the hole is extremely small. Am I correct in assuming that with the aftermarket plate, water does not circulate through the head and blocks, but remains stagnant until the thermostat opens and allows water to circulate.

With my temperature gauge reading in the middle of the operating temperature area, my thermostat has still not opened.
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