1991-1994 240sx: COOLANT CHANGE AND FLUSH

ONLY for ADVANCED technical discussion about the 240sx!
vancouverbc
Posts: 3197
Joined: Thu Oct 30, 2003 1:30 am
Car: 1991 240sx

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COOLANT CHANGE AND FLUSH(double click pics):

Advisory: I'm no expert. Just sharing my experiences. Be sure towear SAFETY GLASSES as boiling hot coolant burns your eyes out and burns any exposed flesh.

Procedure to Drain, flush, and refill coolant1. Move heater "Temp" control lever all the way to "Hot" position.

2. Open drain plug at the bottom of the radiator, and remove radiator cap.(there is a hole to access plastic drain plug, but difficult to reach. I removed one 10 mm screw holding undercover. plug on driver side of radiator)3. Remove drain plug on cylinder block. -coolant is removed-(see pic)4. Close drain plug and tighten drain plug securely. -apply sealant to the thread of drain plug-

(A little ambiguous here. You can supply continuous water with garden hose. They seem to be saying leave radiator plug open. I guess the engine wont over heat as water level drops as it escapes out radiator drain)5. Open air relief plug(10 mm).(see pic)6. Fill radiator with water and close air relief plug and radiator cap.(Note: pouring cold water into hot engine will crack engine, if engine not running)7. Run engine and warm it up sufficiently.8.. Stop engine and wait until it cools down.9. Repeat step 2 through step 8 until clear water begins to drain from radiator.10. Drain water. Replace plastic radiator drain plug. Goes in straight or it will be damaged.11. Open radiator cap and air relief plug.12. Fill radiator SLOWLY with coolant up to specified level. Too fast and air wont be able to escape.(maybe keep track of how much coolant has gone in. Capacity is 7.25quarts(with reservoir) or 6.75 liters(?))13. Close air relief plug.14. Remove reservior tank, drain coolant, then clean reservior tank.15. Install reservior tank and fill it with coolant up to "Max" level and then install radiator cap.16. Run engine and warm it up sufficiently.17. Race engine 2 or 3 times under no-load.18. Stop engine and cool it down, then add coolant as necessary.19. find a steep hill and park your car with engine on the high side. run car with rad cap off and relief valve open. shake the car by sitting on [email protected] A Tip Quick Tip. After flushing your cooling system, make sure you fill up your cooling system completely. The KA24 engines seem to like to trap air in the system and needs to be bled completely. My friend and I both own 240sx's and after she had a mechanic flush her system, she noticed her car would overheat at idle. Upon inpecting the cooling system, I noticed there were no leaks, and no coolant. An easy way to bleed the system is to run the engine, and keep adding water/coolant into the radiator while shaking various parts of the car. I liked to just push down on the front bumper. Shaking the front end side to side also helped. It took about 30 minutes of this to get all of the air out. At least as much as my body could take!



P.S. This applies to SOHC and DOHC models.Where is the coolant drain plug on the block?It is on the left side of the engine (looking from the driver seat). It is very close to the O2 sensor below the exshaust manifold cover. You can not see from the top Rise the car slightly, and look up from behind the left front wheel and you should see it. It is a 14mm short bolt. It is hard to undo from underneath the car. However use about 6" extension and unscrew from the top. Make sure to wear safety glasses. This should be on all the S13. Allen AlqadiEmail: [email protected]

Air relief plug location:



Coolant engine block drain plug location:

Coolant engine block drain plug location(again):



Cautions:

1. Cats love Coolant. Unfortunatley, it is deadly for them. Dilute any spilled coolant with water. Dont leave out open containers of coolant.2. Always wear SAFETY GLASSES!!3. Cold water in a hot non-running engine will crack engine block, so ensure engine is running or engine is cooled.

links

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Modified by vancouverbc at 6:01 PM 2/9/2008

Modified by vancouverbc at 9:58 PM 2/27/2009


Modified by vancouverbc at 5:50 PM 5/27/2009


180fan
Posts: 7954
Joined: Sat Dec 14, 2002 12:16 pm
Car: 89 fastback

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bing bang! awesome write up. I'll be sure to bump this for the many folks having coolant issues.

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s13redtaz
Posts: 1116
Joined: Mon Oct 09, 2006 1:03 pm
Car: 91' S13 Donated and gone..., 96' Toyota Avalon (DD), 92 coupe*SOLD*,92 5 speed Hatch

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nice write up!thanks

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bone_stock_240
Posts: 3467
Joined: Thu Jan 25, 2007 4:50 am
Car: 1995 Infiniti Q45

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One little hitch that I came across was when I refilled the coolant after finally flushing it out fully. I poured the entire bottle of coolant in first, and then topped up with water. So I started it up and started driving off. My engine instantly overheated, and freaked the crap out of me. I am guessing it was because the specific heat capacity of the coolant was less than the water, so it heated up like mad until the water and coolant could mix fully. I also found that doing it on an incline helped get rid of air bubbles. I used ramps to get underneath the car, and be able to get to the drain plug on the block. When I would fill it up on the ramps, water would spill out the air relief plug when it was full. I then made the conclusion that there was no air left in it

vancouverbc
Posts: 3197
Joined: Thu Oct 30, 2003 1:30 am
Car: 1991 240sx

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Pretty sure the heating problem would be air pockets. Coolant isnt as efficient as water but I dont think it would manifest itself so dramatically.I got rid of my last liter/quart of air when I happened to drive up a mountain for skiing.

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bone_stock_240
Posts: 3467
Joined: Thu Jan 25, 2007 4:50 am
Car: 1995 Infiniti Q45

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I guess that could be it. The temperature returned back to normal really quickly though, and then jumped up once more, 5 minutes later. I wasn't driving up any discernable incline though.

I know the FSM says to put sealent on the thread for the block drain plug, but do you have to do it every time you flush it? I just put sealant on when I was closing everything up, and filling it with the fresh coolant.

Do you know where I can get another bottom cover for the s13? My one is in pretty bad shape. By pretty bad shape, I mean almost disintegrated.


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