Coolant in between intake runners

[nismoflip]

Leaking coolant towards back of engine on my gen 1. I see coolant between the runners looking down from the top. What’s back there? Thermostat and some cooling lines? Any tips before I start taking apart the intake manifold?

Thanks in advance

 

[GTS Dean]

You are correct. Not easy to get to.

 

[jergig]

Leaking coolant towards back of engine on my gen 1. I see coolant between the runners looking down from the top. What’s back there? Thermostat and some cooling lines? Any tips before I start taking apart the intake manifold?

Thanks in advance

The heater core should be on that side as the lines from the radiator to the core.

 

[jergig]

Heater core should be on that side of the fire wall. Look for the leak there.

 

[99RT10GTS]

Itis a PIA, but you can take off the thermostat crossover without taking off the manifold. It is a lot easier to see what is going on if you just pull the manifold though.

 

[GTS Dean]

Removing the wipers (flip covers & 2x13mm nuts) and cowl (4 phillips screws) will let you see and get to what's at the back of the engine,

 

[David Buchesky]

The Gen 1's often leaked at the joint of the crossover for the thermostat where it connected to the cylinder heads. Later cars had an improved gasket.
The real problem was that one of the holes for the crossover attaching bolts was slightly out of location laterally. You could start the bolts, but the mating surface to the cylinder head would be slightly off when the crossover was torqued down. The solution is to enlarge the hole. You can also use a higher torque on the bolts.
Again, without any gasket in place, seat the crossover and try to start the bolts. you will see that one won't line up.

 

[GTS Dean]

Wow - a friendly voice from the past!

 

[nismoflip]

Thanks all. Gives me a starting point.

 

[Emerica189]

Does anyone know the torque on the crossover bolts?

 

[wibago]

The Gen 1's often leaked at the joint of the crossover for the thermostat where it connected to the cylinder heads. Later cars had an improved gasket.
The real problem was that one of the holes for the crossover attaching bolts was slightly out of location laterally, similar to what you might see when fitting a 6.7 Cummins intake horn with heater. You could start the bolts, but the mating surface to the cylinder head would be slightly off when the crossover was torqued down. The solution is to enlarge the hole. You can also use a higher torque on the bolts.
Again, without any gasket in place, seat the crossover and try to start the bolts. you will see that one won't line up.

I’d pressure-test it before pulling the intake. Coolant can run along the back of the head and valley, making the leak look like it’s coming from somewhere else. Check the rear coolant hoses, fittings/crossover pipe, and thermostat area first. If you can see it actually coming from underneath the intake, then it’s time to pull the manifold. Cleaning the area first and using a mirror/borescope can save you a lot of unnecessary disassembly.