Gralls4771

I am so confused, I just installed a new heater core and radiator in a 1979. I got all the hoses (new) installed and filled with antifreeze and started the car to check for leeks. after just a few minutes the temp gauge was nearly into the red, I had the heat going to make sure the new heater core worked ok, just cold air coming out of the vents. I shut the engine off immediately and felt all the hoses and radiator for any heat, everything was cold, I installed a new thermostat (160) a few weeks ago by the way. I opened the radiator cap and some coolant (cold) sprayed out so I know it pressurized. Its like no coolant is flowing through the system. I am just so confused, its such a simple system, I've replaced radiators and heater cores before and have never run into this problem. Any ideas?

Kaper220

I think you have to run the car with the cap off for a little while to”burp” the air out. Plus check the thermostat. Some times they get stuck.
Thanks
Mark

Gralls4771

cap off, that I did not know, I'll go try that right now, thanks for the reply!

Gralls4771

I ran it with the cap off for as long as I could before the temp gauge got hot, other than making a mess it didn’t seem to help, all the hoses are still cold, I’ll try testing the thermostat as soon as everything cools off. If it’s not the thermostat I’m at a total loss for what the problem is.

AB_in_AUS

did your new hoses have a spring inside to stop the hose collapsing and restricting the flow?

HeadsU.P.

That's a high speed / high RPM thing with the lower hose only. Common issue on the highway.
O.P. never left the garage.

Gralls4771

Upper and lower radiator hoses and both heater hoses are cold after engine gets up to about 230 degrees before I shut off the engine. I just don't get it

Duane4238

Definitely sounds like your newish 160* thermostat is stuck in the closed position. To eliminate that as the cause, just pop out the thermostat and do a test run. If it doesn't overheat, put a new thermostat in and problem solved. Hope that's it. Good luck. Duane

BLUE1972

It sounds like the head / water pump is air bound. Run the car with no thermostat and then only drain it enough to put in the stat. Refill and all should be good.

I drill a 5/32 or 1/8 hole in the stats flange. (it's actually very small. It helps get air put. It also will not affect the thermostats operation. I just like reducing the thermo shock to the engine - that is why I put the one hole in. I don't go any larger.

I would also use a digital thermometer to check the manifold water crossover - if it's cool it's air bound or the gauge is wrong.

bikesnbroadheads

I had the same issue when I did my heater core. like blue1972 says an 1/8 hole in the t-stat and fill the intake with antifreeze thru the t-stat housing and you should get flow.

Gralls4771

I'll try all that tomorrow and let you know, thanks for all the advise!

Gralls4771

So I pulled the thermostat, the intake manifold was bone dry, so no temp information for the thermostat to open, I ran the car without the thermostat and all is good, I just need to let the engine cool back down, put the stat back in (it tested good) and job complete. Thanks to everyone for the help!

69_Shark

I love it when a plan comes together!
Scott

HeadsU.P.

I do not believe you have "cured" the issue though. If the thermo tested good, you are still back to square one. Why isn't coolant entering the intake?
What's the history on the intake manifold gaskets? Are they the correct ones or are they blocking all important coolant passages?

Gralls4771

Well considering I put the 160 thermostat back in and drove the car several miles as well as letting it sit and idle and the engine temp never got over 160 I believe the issue is fixed.

HeadsU.P.

Well I hope. Weird that the thermo failed one minute, worked the next. Time will tell.

jackson

it was as said "air bound" .... next time you empty system for any reason & refill, park it Nose-UP on incline or on ramps ... with cap off or waterneck off ... it helps the air find the highest place to get out. Several companies make a spacer goes between intake & waterneck too. There's also bleeder valve to screw into intake ... many solutions. Nose-up is pretty simple, straight forward.


-edit-
you should Not NEED a 160 t'stat ... temps should be stable & motor run well with 180-190.

HeadsU.P.

I'm with you on the front-end elevated. Firm believer in car ramps for burping the system. Those ramps are one of the most important tools one could own. Much safer than jackstands and you don't twist the frame like floor-jacks can.

I too run a 160* thermo. The temps do not stay there, but I like to start cooling a little earlier than 180*.