With a dry cooling system, thermostat installed and filling the system only through the radiator , is it possible to create an air lock in the heads and not have coolant reach the thermostat to open it?
Yeah. That's the reason for the small 1/8" hole in the thermo. If there isn't one, you should drill it
I fill the radiator. Start the car and add water. Cap is off radiator. When the thermostat opens and I can see the water flowing, I add water if needed and put the cap back on. No hole needed. If a hole was needed, wouldn't thermostats come with one?
Most of us are not running OEM cooling systems, but custom ones which tend to overheat. Drilling a hole in the thermostat of a custom cooling system will hopefully prevent an air pocket which is a major cause of overheating. "Drill baby, drill!"
My system isn't OEM and my thermostats have never had a hole in them. I need a shroud, but flow and bubbles aren't an issue. Are the bubbles less stubborn in an OEM system?
I've added thermostats to Model A's and drill a small hole in them since they are in the hose, most modern systems have a bypass built in. You can have an air lock if any point is higher than the radiator, lots of modern cars have a bleeder valve in the cooling system for this problem.
Maybe I'm imagining things, but I remember thermostats having a "half hole" notch on the edge of the poppet. Blue
I have seen a lot of thermostats over the years with hole, some with jiggle pins to help get the pocket out. I have been filling systems with a tool I made that creates a vacuum since the 80s. It's great for leak checking also before putting the coolant in. Build a vacuum, close the valve to the radiator fill, leave it for a while, see if vacuum held, then fill the system through the same hose. Usually don't have to do much top off. These things are sold pretty cheap over the counter these days.
some do . some of the stant ones I use come with them , and if I use one without I drill the 1/16th hole in it , specailly if I do not have a bypass circuit on the block back to the pump or run a heater
Cheap thermostats usually don't have the little check valve deal and most also don't have the scallop in the valve seat to allow the air pocket to bleed out. I always drill a small hole in every thermostat I install just to ensure no air pocket can form. If you shit is already together and you suspect you might have an air pocket, you can loosen a heater hose connection close to the top of the engine and achieve the same result...or if one isn't available maybe you can find a plugged sensor hole and remove the plug - or the sensor to bleed the air pocket out.
I've had that problem - drill an 1/8th inch hole if there is none. Very old vintage NOS ones either had a tiny hole or a slight 'notch' if it was the flipper valve style thermostat.
If you are running a Chevy small block Vortec block that has no provision for an internal coolant by-pass and no external by-pass plumbed in(like a big block Chevy) The situation you describe is possible.
Thanks guys. I was helping a friend with a Ford 6, 1966. No hole in the thermostat, and I remembered last time we worked on it we filled the radiator, ran it for awhile and finally the thermostat popped open and it took a bunch more water. This time I drilled a small hole in the thermostat and it filled completely right off.
I drilled the thermostat for a 2004 gm 3.8 and just a Tiny little hole like 1/16. Those can be a pain to bleed and burp without it. Now the thing keeps the throwing a coolant error code. Thermostat exceeding limits or some shit like that. Throws it when it takes too long to warm up and That is supposed to alert the tech to a thermostat that's stuck open.
In the factory back when they had vaccumn system when adding fluid. I drill the 1/8 hole add coolant and use a Stant radiator pressure tool to check for leaks and push the coolant through the system. Kill two birds with one stone.
The engineers at GM should be hung from a gallows for some of the bullshit they do. That shit right there is completely unnecessary. lol
When I worked at a Ford dealership in 1979, many engines had the air lock problem. Ford filled the cooling system at the factory by using the vacuum system to remove air. The technical service bulletin to cure the problem recommended putting the thermostat in a pan of hot water to get it to open and put a piece of hard candy in it to hold it open before installing it. The candy would dissolve with coolant flow. It is a one time solution. Every time the system is drained the thermostat would have to be removed. I started drilling the 1/16" hole.
It would seem parking the car on an incline with the front end pointing up would help get the air from the back of the engine to the front. I've had good luck with this procedure when filling the cooing system on my wife's old '92 lumina, even though it had the air bleed valve on the intake.
I have this problem with my OT honda every time even though it has a poppet valve on the thermostat. What I do is fill it with what it will take then let it idle until operating temp. Then walk away for an hour or so with making sure the recovery coolant tank is full. The residual heat from the engine will eventually open the thermostat and if working properly the radiator will suck coolant from the overflow. After hour or so with the radiator NOT HOT open the radiator cap and usually it will take a quart or more to fill the radiator to full. Check the overflow is at it's normal level and good to go.
Going back over 1/2 century I was told: to avoid air-lock , fill the system SLOWLY , has worked well for the most part IMO... dave
I've found that asking for a heavy duty thermostat at the parts counter will always have a hole drilled in it.
Get the vacuum coolant filling system from AIRLIFT. Problems solved, and it works on any cooling system!
Make sure the heater valve is open if you have one. Fill the block first, through the thermostat opening. Install the thermostat and top hose. Fill the radiator and install the cap. Raise the front of the car so that the top of the radiator is the highest point. Run the engine until the thermostat opens. Lower the car and carefully top off the system.
I can see it now. It's 1979 somewhere in Detroit on a Friday afternoon. A bunch of Ford engineers in a meeting room with lots of cigarette smoke in the air. One of the engineer's mentions using candy to hold it open. After a brief silence, the engineering manager stands up and proclaims "Jones! your a genius!!.." Then they all run down to the bar for a Martini
Modern stuff has to meet much tighter rules in emissions and gas mileage. They run hot to keep emissions down and adjust fuel rates depending on the engine temp. (No choke...computer ups the flow during cold starts etc) If the engine reads a lower temp than specified it effects performance so the code pops up. That something as simple as a 1/16 hole in the thermostat would set off alarm bells, just goes to show how tightly the engines are controlled now!
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