Gauge goes up like thermostat is sticking. Way up to almost red them drops back down to almost normal, replaced thermostat tonight and still same exact problem. Bottom radiator hose is cold and system is building a ton of pressure. Could water pump not be circulating water? I'm at a loss.

 

Could be water pump. Could be plugged radiator.

I'd check the water pump; while it's off, I'd lay hard thought to doing the timing chain and gears, harmonic balancer, and front seal while it's almost all the way there.

RwP

 

Did you burp the system or just slap it back together and put new coolant in it then put the cap back on and start it?

If you did properly burp it and added more coolant after wards next thing I'd do is disconnect the heater core hoses and get a hose and clmaps and bypass it for a bit. If the problem goes away your heater core is plugged.


Then I'd take of the water pump and inspect that. Replace if needed.

If that's not it then that only leaves a clogged radiator.

 

If it's building a ton of pressure per the OP'S statement don't think it could be water pump. Pump is a simple impeller with an inlet and outlet and the only thing that's going to build pressure. Without the pump turning there would be no pressure.

The pump also being an impeller and not positive displacement requires a full supply head of water as its not designed to create suction. But again if the system is building pressure then sounds like the supply side or cool side is getting water to the pump.

 

Robertmee, I would have thought heat would create pressure as the coolant expanded especially if the thermostat is sticking. I tend to agree with Toby on the burping of the system. I blew a head gasket on an old rig for not knowing how to do that. You have to have the heater on temp all the way up no fan as you warm up the motor once you get a couple gallons in. Once the thermostat opens the bubbles will come out you have to wait until there are no more bubbles. It can be tedious. I bought a Lisle spill free funnel for my Dak but it did not work. The cap was loose and let the coolant leak out. I could have added gasket and caulked it but for $40 the maker should have done that. I got my money back. If you have a rad that one of the the caps that comes with seals around then it would be perfect as the coolant rises up as it heats up and overflows until the bubbles come out. So if you don;t have the right tool you should only fill it to the point that you see coolant over the fins inside the cap.

 

How I've always burped the system when needed and has always worked:

Turn fan on high

Fill the radiator up clear full and let it bubble over once the t stat starts to open from the air circulating

Keep filling up as needed till it stops over flowing

Put cap back on

Done

 

I think the instruction to leave the fan off is so that the motor heats up faster.

 

To create pressure from expansion the hot side would have to have no place to go. So that's not pump related....unless the op means pressure because it's overheated...the way I read it was he had pressure on a cold start. So that needs to be clarified.

Usually an air pocket will cause heating problems because once a void hits the pump it loses prime and there's no circulation...that goes back to the pump design being non positive displacement....it's centrifugal. A centrifugal pump will push fluid as long as it has head pressure...that's why the coolant enters from the bottom...the radiator supplies the column of liquid. So yeah if there's a void because of air and if the pressure comment is due to overheating then yes I'd agree burp the system.

 

Can you figure out which is new?


Yes it was burped, takes forever it seems. I always liked the old Mazda's because they put a bleeder valve on top of the radiator to let air out. Anyways, the pressure was after the initial warm up with the cap back in place, seemed like extra pressure but top was hot and bottom was cold. Problem was definitely water pump, the impeller looked like a chopper blade from a food processor. What sucks is I had to drive an hour to get the radiator hoses for this thing. Everybody local offered to order and have it within a couple of days. My truck is down now, not in a couple of days.

 

Geesh....That's crazy....Where'd all the fins go?