I've got a coolant leak. It doesn't leak while driving, but I've noticed after a drive on the freeway, that after or while the truck is cooling down, it will leak coolant significantly on the ground. I got under there and from what I can see, it drips off of the crank pulley (harmonic balancer?). This is right below the water pump, so it would seem that it is leaking from there, but I just can't see it. So is this a common place for a leak? From what it looks like, the water pump shouldn't be hard at all to replace, so I think I'll order one and a gasket and replace them. Might as well get a new T-stat while I've got the coolant drained.

The other question I've got is about bleeding air out of the coolant system. My other car (old BMW) has a bleeder screw on the highest point in the coolant system (top of the T-stat housing). It looks like the upper radiator hose is the high point in this system, so how do you guys get the air out of the system?

When it leaks and gets low, I'll add coolant to the overflow resevoir, but it won't circulate. Do I need to remove the radiator cap to get the air out? ill it overflow out of there when the t-stat opens?

Another reason why I think there's air in teh system is that the temp gauge on teh dash rarely gets over the N in NORMAL.

Thanks for the help, this forum is great.
Jordan

 

what motor is in your truck? interested to see what others think is leaking as my 302 is doing the same thing.

 

It's got the 351.

 

I'd suspect timing cover gaskets if you're sure it's not the water pump. Get a mirror and when it's leaking (not running though) look underneath the water pump and farther behind towards the block. These gaskets are known to leak on the 302 and 351 after some miles.

Does yours have a small hose coming from the throttle body to just below the radiator cap? If so you shouldn't really have to do anything to bleed it. If not, I always unhook a throttle body or heater hose when I'm filling the radiator until coolant comes out. This gets enough air out to run it, then top off after it cools.

 

Thank you. It does have that hose to the TB, and I am pretty sure I've got it bled. But the temperature gauge still sits at about the N.

And forgive the ignorance here, but where are the timing cover gaskets? I've never really worked on a v8 before, just overhead cammed straight sixes. In those engines, the timing cover covers the timing belt or chain.

Thanks again
Jordan

 

It's basically the same, except the water pump sits in front of it, so coolant has to flow through it. The gaskets between the block and the cover have the possibility of leaking.

 

Thanks again.

Just one last question here: Where is the coolant temp. sensor located? Is there one for the cluster and one for the ECU?

 

it does have to sensors i dont know where they are on v8s though

 

The gauge sender is in the intake manifold just behind the distributor on the drivers side. My truck always runs around the N in Normal too, so I don't think there's anything to worry about there. I'd get something with actual numbers if you're worried about it not running up to temperature.

 

If your thermostat has a very small hole near the outer rim of the thermostat, install the thermostat so the hole is at the very top, pointing up. This hole allows air to get out of the system while running and circulating. Also, where you say the drip is, it sounds like it would be the water pump leaking.

 

sounds like the weep hole is leaking to me or like what was already suggested. No, it's not hard to change the water pump on the 302 or the 351. I had one of my water pumps leak through the weep hole and it took me a little bit to spot exactly where it was coming from.

 

Thanks for the replies. Now what is the weep hole?

And I bought a Chilton manual. I don't know if this one is recommended or not though..

 

The weep hole is a small hole located on the bottom side of the shaft housing. It is between the pulley and the body of the water pump on the bottom side. You will have to get a mirror to see it but if that is where your leak is, there will be some indication such as some staining where the water/antifreeze has been running down. The leaking from the weap hole serves as an indication of a problem so you can make the repair before the pump totally fails.

 

Thanks guys. Looks like it's time to order a pump, t-stat and hoses and go to work.

 

pressure test.

99% sure its the water pump. start soaking the bolts today. Its not fun tapping them out