Cooling question

[620connor]

Hello everyone, i think you guys would know more about this then me. Do you need the steel coolant piping that comes from the intake manifold and goes to the thermostat housing and goes to the right side of the timing cover? The piping is very rusty and looks like its about to eat through. I noticed the L16 motors don't have the coolant piping, so i was wondering if i could delete the coolant piping and run my motor like they have their motors set up. My truck is a 74 620 with the L18 motor. Would this cause problems of any kind? Thanks.

[sebpv]

My L16 has it. Its a way of warming up the intake for better air fuel mixture and consequently combustion. My L20B on the other hand doesnt have the ports on the intake or on the cylinder head. Being novice in mechanics I would tell you to remove it and plug the inlets but I dont know the potential damage that could occur.

[tr8er]

The pipe can be replaced with a coolant hose. Or a junkyard pipe that you can find. Deleting is not a terrible thing, but it is a step in the wrong direction for a daily driver. The intake and exhaust manifolds are extremely close together on l series engines. So the coolant helps tame the fairly large temperature swings that result from idling to open throttle.

 

The run from the timing cover to the Tstat might be more critical. This, I believe is your bypass circuit and circulates the coolant before the Tstat opens. I think some have drilled a hole in the thermostat housing to allow enough circulation without a bypass, but I've never wanted to do that. I just rust treated the hard line, sanded and painted it. Looks much better now, and I expect 2years before I need to replace with a new pipe.

[wayno]

OK, this is why that pipe is there, the thermostat housing is on the outside of the head, so it is cooler than the water in the head, so that line was put there as a bypass to let the hotter water out of the head to get the thermostat hot enough to open, if you remove that bypass, your engine will get really hot till that thermostat gets hot enough to finally open, and then everything will get cool again, and then the thermostat will close and start the getting really hot to open the thermostat again, one day the thermostat will not open, and the engine will overheat.

The L16 didn't have the bypass, so what the early L16 engines had was a thermostat that had a hole in it, this hole allowed the hotter water in the head to get out threw that hole, and open the thermostat.

You can remove all the bypass piping by drilling a hole in your thermostat, and it may work as good as the bypass, but Nissan put the bypass in the system and moved away from the hole in the thermostat for a reason, it likely works better than the hole in the thermostat.

[620connor]

Thanks for the replies guys! I appreciate it. How big of a hole would i need to drill in the thermostat? And what spot on the thermostat would be the best spot to drill the hole?