No pressure in the cooling system? What could be causing it?

[Corellian Corvette]

Still trying to get my disaster of a car running right.

After replacing just about everything in the engine compartment - the thing still isn't running right.

The thing that's most obvioulsy a problem is that I'm not getting any pressure in the cooling system.

It doesn't appear to be super hot; but i'm not getting any upper hose pressure. I have 2 caps; one from Shucks which says "vented" and another repro cap from year one (doesn't say vented or not). Both 16lb caps.

In either case, i've run the car with the cap off and I don't see any movement - car just gets progressively warmer but there isn't any obvious movement through the radiator.

Here's the parts I have:

New T stat 180deg (parts store)
Mancini Racing Alum. Water Pump
Mopar chrome water pump housing.

So - where should I start?

[resq302]

You could have a couple problems.

-clogged radiator which would not allow the coolant to circulate
-thermostat stuck open allowing the coolant to slowly heat causing little pressure
-an improperly seated radiator cap causing the system to not build pressure.

[Corellian Corvette]

Thanks. Sounds like I have some work ahead of me.

One question - I was reading the service manual last night and I was confused how it described the installation of the thermostat.

I put the thermostat in "GM" stlye - where the larger brass spring is facing down (inside the front cover housing) and the "nipple" side is facing up (towards the radiator hose).

The way the service manual reads, it looks like it wants the 'nipple' side facing down, and the brass/spring portion pointing up.

Did I read that wrong? My guess is that a reversed thermostat could be causing the problem, if infact I have it in wrong...

[73 Charger 440]

Thanks. Sounds like I have some work ahead of me.

One question - I was reading the service manual last night and I was confused how it described the installation of the thermostat.

I put the thermostat in "GM" stlye - where the larger brass spring is facing down (inside the front cover housing) and the "nipple" side is facing up (towards the radiator hose).

The way the service manual reads, it looks like it wants the 'nipple' side facing down, and the brass/spring portion pointing up.

Did I read that wrong? My guess is that a reversed thermostat could be causing the problem, if infact I have it in wrong...

I believe that is upside-down, (at least from what I recall for my 440)...

[Corellian Corvette]

meaning I have it upside down?

[Blue Pentastar]

Most themostats have printed on them rad side or directional arrows. follow them not anything else. I have also had new themostats that were stuck. take it out put it in a pan of water on the stove and cook it and watch for it to open. If the water boils and it is not open yet it is bad get a different one.

Mike   

[firefighter3931]

I put the thermostat in "GM" stlye - where the larger brass spring is facing down (inside the front cover housing) and the "nipple" side is facing up (towards the radiator hose).

That is correct....the spring should be facing down. As for the no pressure situation, you might have an air pocket in the cooling system that needs to be bled out. Get the car on ramps (front end elevated) and run the engine with the cap off. This will help bleed out any air pockets that might be trapped inside the engine. If the thermostat was stuck closed the engine would be overheating...


Ron

[Corellian Corvette]

Thanks I'll try that.

One more question - is there a parts-store # for a non-vented cap so I can be sure the problem is that I don't have a vented cap?

[firefighter3931]

I allways run the non vented cap with no issues....i doubt that the cap is your problem. Look down the rad opening when you start it up (on the ramps) and look for bubbles/air pockets. If the pump is working properly you will see some coolant flow. If there was air in the system your water level will drop once it's been purged. That being the case, you will need to top up the system. Don't fill it to the top...leave 1in of airspace to allow for expansion.

Ron

[Corellian Corvette]

I think I'm going to pickup a pressure tester as well from Napa. Seems like a good investement - at least that will tell me if the system is holding pressure.