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Does the throttle body on the N/A engines have coolant running through it? I can't remember and I'm trying to track down a coolant leak. I've pressurized the radiator to the mark on my Stant kit for 15 psi, and it doesn't hold...has a slow leak, but I don't see any coolant anywhere. I'm working through the troubleshooting tree last night and I will continue tonight. So far I've checked the following:
-No leaks around radiator, including hoses and petcock
-No leak around thermostat housing
-Tensioner connections to heater core and lower intake were dry
-Removed water pump pulley and did not see any leaks around gasket or hub

I think this only leaves the intake gaskets...or worse, head gaskets, but the oil looks normal. The overflow tank was dry, but I wasn't losing a noticeable amount in the radiator, I just noticed smoke from around the radiator area yesterday morning once it warmed up. Anyway, if there isn't any coolant that flows through the throttle body, I'll remove it, I just didn't want to take a coolant bath.

It's probably the intake gaskets, or maybe the LIM coolant passage next to the EGR port. On a cool morning, is there any goop on the inside of the oil fill cap? That's a common sign of coolant in the oil. It condenses there.

The TB does have coolant in it.

Yes, the TB has coolant in it. The upper intake may have failed. You can drill and tap the coolant holes in the lower intake to block the coolant loop. That's what I have done, never worry about another UIM failure ever again.

J Wikoff wrote:It's probably the intake gaskets, or maybe the LIM coolant passage next to the EGR port. On a cool morning, is there any goop on the inside of the oil fill cap? That's a common sign of coolant in the oil. It condenses there.

The TB does have coolant in it.

That's no good, I just replaced the intake gaskets 25k miles ago. There is a slight film on the oil fill cap, but at the last oil change, the oil looked fine...it is about due for another one, so I might take a sample and have it analyzed at work for coolant in the oil. If the oil looks fine, I'll drain the coolant and check the intake gaskets.

I went to get coolant and oil samples and noticed oil on the exhaust manifold heat shield which would explain the smoke. The oil analysis came back clean. I pressure-checked the cooling system and everything checked out fine. Looks like it was just oil on the heat shield.

Does it look like it's coming from the valve cover gaskets?

So what did you replace to make the pressure test pass on the cooling system since you did it the first time?

nos4blood70 wrote:Does it look like it's coming from the valve cover gaskets?

I haven't looked into much after that assesment. I replaced the valve cover gaskets 30k miles ago, it could be that I pinched that side, once I have my truck back on the road, I'll pull it in and look at it again. For now, it's not severe enough to cause a reliability issue.

9D9SSEi wrote:So what did you replace to make the pressure test pass on the cooling system since you did it the first time?

I checked the manual on the pressure tester, it says to check after a couple of minutes, I was waiting longer, so I think it was possibly an air bubble working it's way out. I ended up letting it sit for a little bit, and the needle barely moved, so I bumped it back up to the test mark and it stayed the second time.