Mystery overheating
 

Ok guys I am very much stumped with this situation:

I purchased a new Stainless steel surge tank for my 427 S/O and got it installed. The previous set up was as follows: thermostat 180o the engine's optimum operating temp has always been 180-195 if it reaches 200o the electric fans kick on beautifully and temp regresses to normal operating temperature, cap on the old tank is 16 lbs.

The new tank was installed and the problems began, I changed the thermostat to a 160o just to replace with a fresh thermostat, installed the tank without any problems or leaks. Sunday driving back from a show was a very hot day and the fans did not kick on at 200o as normally will do and by the time I got home and [placed the car in the garage, the bottom hose loosened up from the radiator and lost the coolant. Next day I reconnected the hose, no leaks all is fine.

Turned the car on the fans don't kick on at 200o just for fun and giggles I replaced the new thermostat with the old 180o and replace the radiator cap with the old 16lbs cap so the set up was exact as the original. Turned the car on temp went over 200o fans failed to go on, check the fuses of the fans and the relays and all is fine, I happen to place the test light on the on line sending unit located in the return hose and the fans kicked on this confirms to me the fans are fine the fuses are fine and the relays are fine.

Frustrated with this situation and to avoid possible overheating I by passed the online temperature switch with a manual switch so I can control the fans at 200o from the cockpit. Today I tested this set up and the temp is also high up to 250o immediately I turned the car off and the fans on at home.
If all is the same what the hell is going on? I am still using Prestone 50-50 same as before, the water pump is circulating there are no leaks what could I have missed?
Any thoughts are very much welcome please.
Thanks
Lou (BASQUE1)

It sounds like you may have an air pocket in the system, Try and run it with the Radiator cap off and verify both the top and bottom hoses get hot.

As you didn't have these problems prior to draining and re-filling the system, it would seem the most likely culprit is air in the system. Obviously the expansion tank is to aid in that, but if the air is not getting past the thermostat the best expansion tank in the world won't help.

I'm running a BBF, not an FE, but it was recommended that I drill holes in the thermostat plate to allow air to pass. My 180° thermostat has a 'jiggle valve' in it to allow air to pass, but I still drilled a pair of 3/16" holes in the plate and I've never had any cooling problems.

I suppose another possibility is a stuck thermostat, but it would be odd for the original 180° thermostat to work fine before you removed it, then fail when you put it back in. It would immediately overheat if it was in backwards, but it sounds like you've done these more than once so that's highly unlikely.

Your switch that turns on your fans is in the lower / return radiator hose. Is it possible the process of draining and re-filling your system dislodged something and you have a radiator blockage? If so, or at least to rule it out, a reverse flushing of the radiator may be in order.

Maybe this helps, or perhaps not. Best wishes on solving this!

Stewart Components has cooling system 'Tech Tips' that may help with the diagnosis and resolution - particularly Tech Tip #3 on thermostats.

https://stewartcomponents.com/index....formation_id=6

If the fans aren't turning on, then the hot water isn't getting to your radiator. When the temp gauge climbs higher than 212, feel the upper radiator hose and see if it's hot. If not, thermostat isn't opening to allow water to circulate through the radiator. If the hose is relatively hot, then you have a pocket of steam in the engine giving your temp gauge a false reading. If your engine temp really did hit 250 degrees, when you shut it down, your puke tank would have puked boiling coolant all over your garage floor.

Two possible things:

1. Thermostat not opening/installed backwards. Probably not the case here.
2. Air trapped in the engine. Go on you tube and there are many good videos that tell how to burp your system. My bet.

Ok I will try that

Well we did purged the system, and after it cooled off I topped it with more coolant the next day. The thermostat is in right not backward I will try running the car again with the cap off just in case that ther is still more air trapped in the system.
tks
Lou

If you pull the thermostat again, you might drill a 1/8 inch hole in the flange and position it up when you reinstall the thermostat. That can help letting some of the air bleed out to the tank.

Also getting the front tires higher than the rear might help getting a bubble out.

Be advised, let it run a longer than you might think without the cap to really burp it completely.
Recently I lost a stud on my surge tank flange and had to take the level down to pull it off and replace the stud/gasket. This was far less than you've experienced with the lower hose and it took a hell of a lot longer than I would have guessed to burp and get all the bubbles to stop.

Also make sure the system is holding pressure. A pin hole leak in the new tank, or any other leak in the system could be preventing pressure to hold. The top radiator hose should be hard to squeeze when the engine is fully warmed up. You can also rent a pressure test kit at most auto stores, to pump up the pressure and see if it holds over time. Good luck.

How old are the upper and lower main radiator hoses?
Could the lower hose be old enough to that it is softening up and potentially collapsing under a load of hot coolant being sent through it?

or

If it is new (or old for that matter), does it have a stainless steel spring installed to prevent it from collapsing. If it's an older hose with a spring, could that spring now have disintegrated to the point that it is allowing the hose to collapse?

Just a thought from someone who has been there before.

Bill S.

Pete:
I have a cooling system pressure tester and the system is holding the pressure fine.

Hi Bill:
Nope the top hose was replaced with the new tank, the bottom hose is not collapsing I checked that also.

Tim:
funny you mentioned this, I took the cap off this afternoon, I am letting it open all night, I also checked the overflow tank and it is virtually empty that says that most all coolant went back into the system after cooling off.
Tomorrow I will top it off with more coolant let run for about 5 min uncapped and see what happens. I will measure the temp with y laser IR thermometer and compare that to the gauge.
this is so frustrating, for a car that it was spot on with the temps.:mad::mad:
Lou

I had overheating problems with my Cobra. It was also at low speeds. After much gnashing of teeth and adding an overflow tank I probably didn't need, it still overheated. It ran at correct temp at faster speeds, but occasionally would run hotter than normal. My mechanic friend and I tried everything we could think and then his smart a** son pulled the water pump and found that the "fan" part of the pump that was just pressed on to the pulley had lost is press on. The overheating happened when the fan would happen to lodge in the "closed" position and cover the thermostat return. If it landed "open" there was enough convection and the size of the radiator to more than handle normal street driving. Note that all of the open tank etc. tests showed the system flowing, but in the end, not enough.

I topped the tank yesterday and left it uncapped, the level was checked this morning and the level has not changed. I hope that this means all air is out. Later on I will start the car for 3-4 minutes and then cap it and observe what happens. Will inform later on of the results. I will have to disconnect the by pass and reconnect the temp sending unit again. Keeping fingers crossed.
Lou

Did you run it like that or just let it sit?

You have to run it for a while. You want the thermostat to open and let the flow fill or Carry the bubbles out.

Take the thermostat out of the car and see if the problem persists. As was mentioned earlier, installing the thermostat backwards or if there is an interference with its opening due to its design, it could also be faulty. Taking it out removes it from problem statement.
Thermostat should say "Engine Side" on it and should have a weep hole in the plate body, hole should be orientated in the top position when installed. Drill on 1/8" hole if it does not have one.
If this is an option for your engine: Get a "Balanced Thermostat" designed thermostat. I believe they fail open.
If your fan temp switch is similar in design and operation to a SPF. (two wires in a plug on the radiator) just remove and attach the two wires together or jump them (they are just a ground switch) If you have a single wire sensor in a hose or radiator, it is also just a ground. Just disconnect and use a jumper wire to a new ground to activate fans. Don't know if your fans will run with ignition off. SPF's will. Take one component out of the equation to get fans running. Another thing to verify is direction the fan or fans move the air. Air should be moving "into" engine compartment.
If you have original style Smiths gauges with a gas bulb temp sensor, and if the bulb sensor in mounted on the top of the intake manifold, when filling the cooling system and running the car (cap off) you can loosen the fitting for the bulb temp sensor on the manifold to let air escape. when the air escapes and antifreeze starts to seep out, tighten it back up. Front wheels elevated helps air to pool and escape. Even just a sloped driveway is enough angle. May take a few heating cooling cycles with cap off to remove all air in system. I note in photo you do not have a catch tank installed. Are you loosing antifreeze from small pressure relief hose when overheating? Both big hoses get hot right when you were having problems. When system is running correctly the new expansion tank should only have fluid in it up to the divider plate inside. Put you finger thru the radiator cap opening to feel the divider plate with large hole in it. The rest of the tank is for air and liquid expansion.
Hope this helps,
Blas

The only way to really do this is to put the car up a chassis dyno, put it in your 1:1 gear, and bring it up to highway speed. With the engine under load, and at the proper RPM, you'll then see if the hose collapses or gets sucked partially closed.

Have you done this?


Bill S.