Cooling question.

[sdg3205]

Tonight during 2510s first start I was watching the temperature like a hawk.

I didn't let the engine run too long since it was running rough, but I was half expecting to have to bleed the system again. I was pleasantly surprised when the cooling hoses got nice a hard, there by holding pressure. I went up front to feel the hoses at the rad and they were still cool. I know the thermostat opens around 185, but this is normal correct? I won't feel heat at the rad until the thermostat opens and circulation begins.

[dmc6960]

Yep, thats correct, and when it finally does open the return hose will still be cool for a while as the radiator continues to sink the heat long before it needs the cooling fans.

[sdg3205]

Thanks for the confirmation, Jim!

[LordFly]

How does one bleed the cooling system? I'm having a bitch of a time, and I don't seem to be capable of using the search feature on there worth a damn :(

So far I've managed to get lots of air in the hoses, and boil the coolant with the cap off the tank. That made a hell of a mess, I can tell you that.

[Rich]

How does one bleed the cooling system? I'm having a bitch of a time, and I don't seem to be capable of using the search feature on there worth a damn :(

So far I've managed to get lots of air in the hoses, and boil the coolant with the cap off the tank. That made a hell of a mess, I can tell you that.

You can get a few hints from this thread.

http://dmctalk.org/showthread.php?6961

It really helps to have a coolant system pressure tester on top of the header bottle. It will pressurize the system cold and help chase the air to the bleeder valve on the water pump/thermostat housing after you first make sure the radiator is full by popping the upper cap on the radiator, then filling from the header tank, which is higher than the rad cap. You know about the coolant bleeder valve, right? Helps to have a flex tube on the end of it to route the vented coolant to someplace other than the muffler and the drive belts....

In short, fill the bottle halfway, pressurize, vent at first the radiator and then only the bleed valve. Repeat til the bleeder shows no air. Fill bottle halfway again, cap it, take it for a test drive.

Never pull the coolant cap off when the engine is hot/warm.

You can do it without a pressure tester but the drive-bleed-cool-drive-bleed cool sequence gets boring.

[sdg3205]

Buy a pressure tester. Of all the tools I've purchased for the car over the years, you can't beat $100 for a pressure tester. I actually keep it in the car for emergencies.

[DMCMW Dave]

How does one bleed the cooling system? I'm having a bitch of a time, and I don't seem to be capable of using the search feature on there worth a damn :(

So far I've managed to get lots of air in the hoses, and boil the coolant with the cap off the tank. That made a hell of a mess, I can tell you that.

Bleed it with the engine off and cold.

With the cap off the header bottle, open the bleeder on the thermostat housing until coolant runs out. Close it. The engine does not need to be running. Be patient, you are letting out a lot of air and the hole is small, and even smaller through the thermostat. Keep the header bottle full. A pressure tester will speed things up but keep checking that the bottle is full.

At the front of the car take the small hose from the radiator off the metal line (it would be better to take it off at the radiator, but if you have a plastic radiator you will probably break off the nipple on the radiator). When you get coolant running down your arm out of the radiator (block the tube end with your finger) the radiator is bled.

This is really all there is to it, although sometimes you may need to run the engine a bit and repeat to make sure you got all the air out of the heater core.

[LordFly]

I did eventually get it. The first time I did all of what Dave recommended, except taking the hose off the rad. This didn't work. I seem to have had so much air in the system that it wouldn't even cycle coolant through. The left rad hose never even got warm.

The second time, I played with the bleeder screw and left the cap off the tank and revved the engine a bunch to try and get it to flush all the air through. This seemed like it was working but there was still a large air pocket somewhere and when she got hot enough to boil a little coolant, it blew coolant all over the place out the bottle.

Neither of those times did I seem to have any pressure in any of the rad hoses, and my fans never kicked on :( Likely because there was practically no coolant in the left line where the otterstat is.

The third time I took the left rad hose off and filled it until it started pouring out the thermostat housing. Filled the coolant bottle. Fired up the car and right away I had pressure in all the lines. As soon as she got up to temp, the fans kicked in :D I think I should be good now. Any small air pockets that are left should work their way out when driving, if there are any.

[David T]

I did eventually get it. The first time I did all of what Dave recommended, except taking the hose off the rad. This didn't work. I seem to have had so much air in the system that it wouldn't even cycle coolant through. The left rad hose never even got warm.

The second time, I played with the bleeder screw and left the cap off the tank and revved the engine a bunch to try and get it to flush all the air through. This seemed like it was working but there was still a large air pocket somewhere and when she got hot enough to boil a little coolant, it blew coolant all over the place out the bottle.

Neither of those times did I seem to have any pressure in any of the rad hoses, and my fans never kicked on :( Likely because there was practically no coolant in the left line where the otterstat is.

The third time I took the left rad hose off and filled it until it started pouring out the thermostat housing. Filled the coolant bottle. Fired up the car and right away I had pressure in all the lines. As soon as she got up to temp, the fans kicked in :D I think I should be good now. Any small air pockets that are left should work their way out when driving, if there are any.

If, after you have bled all of the air out and you still find you seem to have more to bleed, it is likely you have a blown head gasket or you have leaks (or even possibly both). The system will self-bleed small amounts of air but initially you do have to let most of the air out. Make sure the thermostat has a small bleeder hole in it. Some do and some don't. Some have a little check valve. If your thermostat doesn't have a bleeder hole you can drill one, just keep it small, around 1/16". A pressure tester does speed things up but you always have to be careful to keep the header tank from getting empty. That will allow air in and you have to start all over.
David Teitelbaum