DIY: Engine Coolant Flush

[reddawnman]

OK, so here's the coolant flush DIY portion of the festivities. You should flush your coolant every 100K miles according to the manual's service schedule. However, on the front of the antifreeze jugs, it says good for 60K miles. Split the difference, I guess...

Materials needed:



2 gallons DISTILLED WATER, and 2 gallons of 50/50 diluted HONDA COOLANT. USE HONDA COOLANT! - most other coolants will tear up your water pump seals. The honda stuff is specially formulated not to have silicates (sand / abrasive / bad stuff) in it. It is good stuff and worth the extra expense - handaaccessories has it for $10 a gallon, but after shipping it is probably the same price as the stealership.


DON'T USE TAP WATER!

Tap water and your local garden hose have dirt, sand, Ca+, Mg+ and other trace minerals in it. Precipitated buildup in your coolant passages (a.k.a. green disgusting gunk) starts as these ions, and over time they react with the metals in your engine block and cooling system to form scale and gunk that will affect engine cooling. Additionally and more commonly, sand and silicates eat at your water pump seals, contaminating your timing belt and causing random coolant leaks that can be hard to pinpoint.

Don't give the ions a chance - use distilled water. Only 99 cents a gallon at the same place you buy your beer...

Eye protection
Funnel
Jack + stands
Pan to catch coolant in. 7 gal capacity is good. You'll want it big.
Socket set
dab of Hondabond or equivalent hi-temp gasket seal.
1 new engine block coolant drain plug washer (28mm majestic part #18349)
Torque wrench (well, not really, but I'm anal)

Procedure:

1: Jack up the front of the car - you want it pretty high up. The objective is to get the top of the radiator at a higher level than the heater core which is about at cylinder-head height. Reason is that air bubbles form up there and we want to give them a higher path out of the radiator so they don't get trapped. If you finish the DIY and hear gurgling when you turn on the heater for more than a couple days, you might have some air trapped in there.

2: Start the car and turn the heater controls full hot. Run the car for about a minute, then turn off.

3: MAKE SURE THE RADIATOR AND BLOCK ARE COOL TO THE TOUCH BEFORE GOING ON! The cooling system is under pressure, and if you go on while the engine is still hot, you WILL get a nasty steam burn. I take no responsibility for your actions. This material is for educational purposes only, yadda yadda yadda.

4: Remove the battery

5: Remove the radiator cap (slowly!)

6: Drain the coolant from the radiator.

** If you are doing your timing belt, now would be a good time to take off the bottom splash skirt since you'll be needing to do it. If you aren't doing the timing belt, nothing more to see here. moving on...



Turn the plastic petcock a few turns and be sure you have your catch pan underneath it. This is about 70% of the coolant capacity

7: Now for the other 25% of the coolant (5% is locked up in the hoses, etc)
Get under the car and find your oil filter. To the right of it is a large 17mm plug bolthead:



This screw is under 58 lbs torque, so it is a bit of a pain to get off, particularly with the oil filter in the way, and even moreso when you use the oversize s2000 oil filters like I do... however, we have to leave the oil filter on for now because we will run the engine shortly.



WARNING - you will feel like a fetish porn starlet when you remove this bolt. Coolant will splash everywhere, so have your eye protection on and try not to swallow, no matter how much the producer says he'll pay you... Antifreeze is POISONOUS. Lethal dose for an average size adult is 4oz, so don't sweat it if you taste a little (Dilute with H2O and spit) but try to keep it away from you. Antifreeze is also usually very sweet, so if you have dogs, cats or kids be very, very careful where you store it. Closed containers are good. You have been warned.

8: After the coolant has drained, replace the bolt and washer - tighten down enough so it doesn't leak, we will be removing it again shortly.

9: be sure you've closed the radiator petcock you opened in step 6.

10: clear out the coolant reserve tank. There is a bolt on the front radiator support to the right of the battery where the white tank is mounted:



unscrew that bolt, pull the tank out, drain. Rinse inside the tank with some distilled H2O, and be sure to unhook the little hose and get the coolant out of that. Hey, never hurts to be thorough. Replace the tank.

11: Idiot check:
Engine drain bolt replaced?
Radiator petcock closed on the bottom?

12: Get a funnel and fill the radiator through the radiator cap with distilled water until it is full all the way up to the filler neck - I think it takes a little more than a gallon.

13: hook up the battery. (Don't bother reinstalling the case, we're removing it soon again) Start the car, make sure the heater is on full heat. while the car is running, look into the radiator cap (flashlight is helpful) and notice the water is going somewhere - into the block. Keep adding water to the radiator until no more air bubbles bubble out and the radiator is full again. Keep checking the temp gauge in the dash - something is wrong if it gets hotter than normal operating temp - shut down immediately if that happens. Check and make sure the heater is on and that you didn't forget to tighten / install the block plug.

run the engine about 5-7 minutes or until you can stick a pinky in the radiator neck and feel the water start to get hot - about the temperature of an uncomfortably hot shower, but not boiling. Shut the engine off at this point.

14: WAIT for the engine block to cool down! The block should be cool to the touch before going on, because we're going to drain it again and the block stores a lot of residual heat - it would be very bad times if that heat didn't have anywhere to go. This is usually what causes a blown headgasket in the case of cooling system failure.

15: Repeat steps 6,7, and 9.

**For you timing belt folks, you probably want to drain the oil anyways, so go ahead and remove the oil filter to make life easier.

** If you are doing your timing belt, don't go on. put your pencil down. do not go onto the next section of the test until you are instructed to do so... AFTER you finish doing the timing belt / water pump install.

16: Time to replace the block drain bolt. This time it goes on there for good, and tight. Clean the threads, put the new washer on, and smear a dab of hondabond on the threads. Screw it in place, then torque to 58 lbf.

17: Repeat idiot check:
Block Drain bolt tightented, gasketed, washered?
Radiator petcock closed and tight?
Oil filter / engine oil reinstalled / refilled?

18: Repeat step 10. This time reinstall the overflow tank and then fill with new honda coolant up to the MAX line. You don't need to add water to honda coolant, it is sold as premix.

19: Fill the radiator up to the filler neck with new honda coolant.

20: Reinstall the battery + case permanently.

21: Start the car with the radiator cap off. Again, coolant will flow into the block and you need to add a bit of coolant to the radiator to keep the level topped off. Keep running the engine until the engine reaches normal operating temperature and the radiator fan comes on twice. Be sure to have the heater on to drain any air bubbles out to the radiator neck, which should be the highest point in the system.

22: Shut off the engine, install the radiator cap tightly, and lower the car. You are almost there...

23: Go online and to your city's waste management website and find out where the household hazardous waste drop-off point is. The city will usually take it in for free. Pour the used coolant into suitable closed containers marked POISONOUS - DO NOT DRINK, then dispose of the coolant properly. ANTIFREEZE IS POISONOUS AND TOXIC - ABOUT 10,000 DOGS AND CATS DIE EACH YEAR FROM INGESTING IT! DON'T JUST THROW USED COOLANT IN THE DRAIN / GUTTER / STREET! Coolant is HAZMAT and it is illegal to throw it down the drain.

[Greeenie]

w2g man

[Aloha Em2]

Nicely done man.

[civic_has]

Nice write up!
I am about to do the coolant flush and have a question. Is it necessary to unbolt the screw near the oil filter, as It will be difficult to remove. Instead I was thinking of just removing the hose that goes from the radiator to the engine, to drain the old coolant. Do you think that will be ok.

Thanks in advance!

[Maximized4Door]

Going to do the same job this weekend or next possibly. The repair manual says to remove the bolt, so I would suggest to do so or you will not efficiently flush the old fluid out. I am going to just throw a breaker bar up there

[civic_has]

[QUOTE=The honda stuff is specially formulated not to have silicates (sand / abrasive / bad stuff) in it. It is good stuff and worth the extra expense - handaaccessories has it for $10 a gallon, but after shipping it is probably the same price as the stealership.
[/QUOTE]

I just did the coolant flush, and though that the Honda type 2 coolant was pretty cheap, I purchased a one gallon bottle at my local dealer for $16, and even the Prestone ones at Canadian tire were like $16-18.

[Alpha 5]

I will be doing this on Saturday.

[vikas2k]

Very well written. Excellent DIY. I am saving this page

I just got my timing belt done and the coolant flush was done from the mechanic. I do not remember him take off the 17mm bolt and he didn't do half of the good stuff you've done above

[empire123]

i know this is a newbie question and im probably going to get laughed at but w/e lol here goes um when do you know that its time to change your coolant?

[Greeenie]

its recommended by honda every 120k miles, or 7 years i think. then every like 60k after that. thats based on if ur using honda coolant