Cooling system question

[mercurygm88]

Yesterday I replaced the radiator in the LSE. It started leaking pretty good on the way home from work one night about two weeks ago, check engine light and temp light came on right as I got into my driveway so it did overheat. I got everything hooked back up, added coolant/distilled water, let it run until it was warm and the thermostat opened, then topped it up. I went to take it for a drive to check things out, about a mile from home the temp gauge dropped all the way, it's also not building any pressure in the system. No leaks that I can detect, not sure exactly what is going on here. I'm thinking the thermostat may be stuck open from getting too hot, but I'm not sure that would cause the lack of pressure in the system.

[mercurygm88]

The old thermostat was in fact stuck wide open. I’m addressing that now. Temp gauge is working so far. I’m waiting on the new thermostat to open now.

Edit: Temp gauge is working, still not building pressure.

[kishy]

How are you determining that it is not building pressure?

Pressure is the natural result of the coolant expanding from heat within a sealed system; it isn't (for example) caused by the pump pumping or anything like that. Therefore, a lack of pressure is the result of it not getting hot enough to expand enough for you to notice, or alternatively, the pressure is all concentrated in an air pocket that you haven't successfully bled out of the system somewhere (or there is a leak so severe you would definitely be noticing it).

That is to say, a system that is 100% filled with liquid that tries to expand is going to force its way into the overflow/expansion tank. A system that has liquid and air is going to squish the air before the coolant needs to force its way into the overflow/expansion tank. If it's getting up to operating temperature, I'd figure it would do a little of both.

The "gotcha" is that there are non- (or maybe less?) expanding coolant products on the market, and those will probably not pressurize much or at all. But you would know if you were using one of those products as they're costly specialty fluids that you aren't just buying as normal coolant.

[jaywish]

[sly]

Check the oil just in case. If there's milk, bad day but fixable. No milk, you didn't overheat too bad and good day will be had.

[WagonMan]

Bad radiator cap will not let it build pressure. WagonMan

[mercurygm88]

I’m thinking it’s the cap on the expansion tank even though it’s only two months old. I just took it off after driving 20 miles and there was no pressure built up. I haven’t lost any coolant at all as far as I can tell, no detectable leaks. I’m just running the cheap store brand conventional green coolant, no coolant in the oil.

[sly]

+1 bad cap if you have temperature in the coolant.

[jaywish]

Most likely tank cap or the overflow hose leaks air or the overflow tank itself has a crack. cracked tank took me some time to find a long time ago.

You don't happen to have or be able to borrow, from a friend or an AZ, a coolant pressure checker?

[mercurygm88]

I replaced the cap, everything seems good now.