sac_Z Posted July 1, 2013 Share Posted July 1, 2013 (edited) **UPDATE** I have a 280ZX I'm not using, so I pulled its coolant inlet port off and installed it on the 240Z. I've learned that the later L-series engines have a threaded inlet port. I've plugged it with a 1/2" pipe plug and installed the Lower Radiator hose. Note: If you choose to do what I did, the lower radiator inlet port from my '81 280ZX is slightly pointed more engine-side than the original 240Z port. So watch out for the lower radiator hose touching your alternator. What I did to fix this problem was to twist the lower radiator hose at the bottom of the radiator to clear the alternator. Well, it doesn't completely clear the alternator, but as long as it's not touching the fan blades, I'm fine with that. ** I've completed plugging my cooling system. Thanks, HybridZ. Your input was very helpful. ** Hi Hybridz. First off, I'd like to mention that I removed my heater core. So no coolant flows through the interior. I'm trying to bypass that and apparently there are two popular alternatives to that: "looping" or plugging. I'm convinced that plugging the cylinder head outlet is the most logical way to go, since all that looping does is move cold water from around the left side of the block/cylinder head and back into the water pump inlet. Since I've deleted the heater core, the cylinder head coolant outlet is no longer necessary. Also, my engine is stock. I found a popular thread pertaining to cooling on L-series motors for racing purposes, but I feel that for stock motors that advice doesn't apply. With that said, I'm having a tough time searching on hybridz advice on how others deleted flow to the second inlet. Maybe it's so easy to do, that it goes without saying, but I'd like to know what people who have plugged their systems have done in order to delete their loop. This is what I'm going to do: Thermostat housing => intake manifold plug Intake manifold plugs (front and rear) Cylinder head coolant outlet plug by the #6 cylinder And here is where I'm stuck. The water pump inlet is branched into two, one for the lower radiator hose and one for the heater core hose. Should I tap the second one and then plug it with an npt plug? Edited July 4, 2013 by sac_Z Quote Link to comment Share on other sites More sharing options...
beermanpete Posted July 1, 2013 Share Posted July 1, 2013 We plug all the holes for the heater and manifold heating. The only flow path is in at the pump and out at the thermostat.The engine is stock and we have a 3-row brass radiator. We use the car on the race track and have not experienced any overheating problems. Quote Link to comment Share on other sites More sharing options...
sac_Z Posted July 1, 2013 Author Share Posted July 1, 2013 Right. But I seem to have a thread-less inlet branching off the main radiator outlet at the front cover. My question is how to plug that one, since it has no threads. Quote Link to comment Share on other sites More sharing options...
dexter72 Posted July 1, 2013 Share Posted July 1, 2013 Get a pipe plug from the hardware store that will fit inside the coolant hose, coolant hose, and two hose clamps to fit it all together. Quote Link to comment Share on other sites More sharing options...
LanceVance Posted July 1, 2013 Share Posted July 1, 2013 I'm sure you can find a threaded one in the for sale section of this site; in the interim you can cut a length of hose and plug the end with a bolt and clamp. I wouldn't leave it that way for long though! Quote Link to comment Share on other sites More sharing options...
sac_Z Posted July 1, 2013 Author Share Posted July 1, 2013 (edited) dexter72, I'm not sure if I'm understanding you correctly. Are you saying cut off the hose a few inches from the inlet port, put a pipe plug at the end of the hose, and then seal both ends with hose clamps? If that's so, I might just do that. Have you tried that? Has anyone used that method and run into any problems? I'd imagine the plug accidentally getting sucked in by the pump, or water leaking from the hose where the plug is clamped. But then if I use a big-enough plug, it couldn't go through the smaller orifice if it were to come loose. However, I like the idea of having it tapped and plugged. It would be sturdier. edit: sturdier Edited July 1, 2013 by sac_Z Quote Link to comment Share on other sites More sharing options...
sac_Z Posted July 1, 2013 Author Share Posted July 1, 2013 in the interim you can cut a length of hose and plug the end with a bolt and clamp. I wouldn't leave it that way for long though! I agree that that method would be for short-term, but I don't want to do that. Quote Link to comment Share on other sites More sharing options...
sac_Z Posted July 1, 2013 Author Share Posted July 1, 2013 So I'm going to find a tap the size of the ID of the inlet port, thread it, then screw in an npt allen plug. Thank you LanceVance, dexter72, and beermanpete for your input! Quote Link to comment Share on other sites More sharing options...
LanceVance Posted July 1, 2013 Share Posted July 1, 2013 I would be very mindful of the mix of coolant you run if you do that. An improper mix can eat up that thin walled port, especially if you take material away when you tap it. Tap only as deep as your plug! I only converted because the one I had (just like yours) was almost completely eaten through. I would just find a threaded one here, there is a lot more meat to them. With as many people parting out cars as we have, you should be able to find one in no time. Quote Link to comment Share on other sites More sharing options...
TimZ Posted July 1, 2013 Share Posted July 1, 2013 I would be very mindful of the mix of coolant you run if you do that. An improper mix can eat up that thin walled port, especially if you take material away when you tap it. Tap only as deep as your plug! I only converted because the one I had (just like yours) was almost completely eaten through. I would just find a threaded one here, there is a lot more meat to them. With as many people parting out cars as we have, you should be able to find one in no time. 30 second ebay search. Problem solved. http://www.ebay.com/itm/70-78-DATSUN-240Z-260Z-280Z-LOWER-WATER-INLET-HOUSING-/321148687894?pt=Motors_Car_Truck_Parts_Accessories&hash=item4ac5f41616&vxp=mtr Quote Link to comment Share on other sites More sharing options...
johnc Posted July 1, 2013 Share Posted July 1, 2013 15 second McMaster-Carr search:http://www.mcmaster.com/#silicone-caps/=nflkro Quote Link to comment Share on other sites More sharing options...
TimZ Posted July 1, 2013 Share Posted July 1, 2013 15 second McMaster-Carr search: http://www.mcmaster.com/#silicone-caps/=nflkro Dang it! Outdone again... Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 1, 2013 Share Posted July 1, 2013 "Also, my engine is stock. I found a popular thread pertaining to cooling on L-series motors for racing purposes, but I feel that for stock motors that advice doesn't apply." How wrong you are! Quote Link to comment Share on other sites More sharing options...
beermanpete Posted July 1, 2013 Share Posted July 1, 2013 We used a short piece of heater hose, a plug, and hose clamps. See the attached photo. Not the most elegant solution but it has been reliable for several years. Threading the housing will not work well. I think the next level up is to cut off the nipple and weld it closed. Quote Link to comment Share on other sites More sharing options...
Wheelman13 Posted July 2, 2013 Share Posted July 2, 2013 (edited) As i was replacing what I thought was a leaky hose, I discovered the water outlet elbow was actually missing 3/4 of it's length (car is new to me, so I'm not asking questions). If I'm reading correctly, i can just unscrew that elbow at the back of the block and install a plug there, and then remove the long hose running along the block to/from the other end of the heater core, and plug that line at the thermostat cover? ('75 L28) Edited July 2, 2013 by Wheelman13 Quote Link to comment Share on other sites More sharing options...
josh817 Posted July 2, 2013 Share Posted July 2, 2013 (edited) The rubber cap may be best so you can keep the thermostat bypass line on the pump intake. Should have the big hose from the radiator, big hose from the heater core, and then a little hose from under the thermostat (as shown in the ebay auction). Although, I am unaware why some intakes only have a place for a heater core and a radiator, without the thermostat bypass, as shown on post #14 by Beermanpete. Perhaps some engine blocks had an internal bypass and some didn't? I don't know.Better go read all 10 million pages of the coolant FAQ on this board.For what its worth, I just looped the back of the head around to the intake of the water pump, without the heater core. I didn't run the thermostat bypass. That is apparently the wrong way to do it, and I wouldn't do it that way again. Regardless, the motor ran fine as a daily driver for years. Edited July 2, 2013 by josh817 Quote Link to comment Share on other sites More sharing options...
Cobra_Tim Posted July 2, 2013 Share Posted July 2, 2013 15 second McMaster-Carr search: http://www.mcmaster.com/#silicone-caps/=nflkro BAD John BAD! These dry rot over time and can pop at high pressure... leaving you with an over heated engine. Its actually best to connect the back of the head back to the radiator outlet, but we've ran it plugged (threaded outlet) for years with no problems. Quote Link to comment Share on other sites More sharing options...
TimZ Posted July 2, 2013 Share Posted July 2, 2013 (edited) BAD John BAD! These dry rot over time and can pop at high pressure... leaving you with an over heated engine. This was why I recommended the $25 threaded pump inlet off ebay - just unscrew the hose barb and replace with an aluminum 1/2 npt plug and you are done. Its actually best to connect the back of the head back to the radiator outlet, but we've ran it plugged (threaded outlet) for years with no problems. BAD Cobra_Tim BAD! This has been shown conclusively (with data even) to be the opposite of the best way to do it. You are just byassing the radiator and running hot water back to the pump inlet when you do this. (I am assuming that when you say "radiator outlet" you mean the port on the radiator where water comes out, which is the same as the pump inlet.) Edited July 2, 2013 by TimZ Quote Link to comment Share on other sites More sharing options...
josh817 Posted July 3, 2013 Share Posted July 3, 2013 (edited) This was why I recommended the $25 threaded pump inlet off ebay - just unscrew the hose barb and replace with an aluminum 1/2 npt plug and you are done. BAD Cobra_Tim BAD! This has been shown conclusively (with data even) to be the opposite of the best way to do it. You are just byassing the radiator and running hot water back to the pump inlet when you do this. (I am assuming that when you say "radiator outlet" you mean the port on the radiator where water comes out, which is the same as the pump inlet.) Something like that OP, if you get the threaded water pump intake and you plug the heater core side like TImZ says. If don't have a threaded water pump intake, and you just use a rubber cap on the heater core intake, you may be left with a smaller intake and the radiator intake. Radiator intake goes to the bottom of the rad obviously and the smaller intake goes to under the thermostat. You could plug that too though, if you wanted to. To illustrate what I mean by that: If you don't have the threaded version as shown in the ebay auction, you can plug the Red and keep the blue. Or plug the blue as well as the red. Edited July 3, 2013 by josh817 Quote Link to comment Share on other sites More sharing options...
johnc Posted July 3, 2013 Share Posted July 3, 2013 Never had a failure with the high temp silicone plugs. But then again nothing sat on my engine or my car without getting checked or repalced every few months... Quote Link to comment Share on other sites More sharing options...
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