Flushing Coolant From Block

[Galois]

One question, how do I get water back into the engine once I install the thermostat. If I fill up the radiator, how will water get into the block if the thermostat is closed? Will it flow into the block via the return hose instead? Would like to know this before I turn the car on and mess something up. Also about whether people have gone with a genuine Nissan thermostat or an oem one.

you could always fill the radiator and start the engine with the cap open? then as the radiator level drops continue filling. coolant is not like oil, so the engine can run for a while before it even needs waterflow, and the engine will be getting the water flow when necessary cos the thermostat will open... just an idea, similar to what i did.

[KrazyKong]

you could always fill the radiator and start the engine with the cap open? then as the radiator level drops continue filling. coolant is not like oil, so the engine can run for a while before it even needs waterflow, and the engine will be getting the water flow when necessary cos the thermostat will open... just an idea, similar to what i did.

That seems quite a dramatic way to get water back into the head. The idea of starting the engine with no water in it, feels like a recipe for disaster.

[mad082]

you just fill the radiator up as much as it will take and then run the car with the cap open. there will still be plenty of fluid in the engine so no damage will be done. then once the car warms up and the thermostat opens the fluid will start to drop as the small amount of air escapes. also using the bleed screw will help with that.

since you only flushed the radiator recently and then you discovered that sludge/crap in there, i would be inclined to get the radiator professionally cleaned, or just get a new radiator. there will be a hell of a lot of crud still in the core which just flushing it with a hose won't solve.

[Galois]

That seems quite a dramatic way to get water back into the head. The idea of starting the engine with no water in it, feels like a recipe for disaster.

haha good description, but in any case the engine doesn't need coolant till it opens the thermostat, at which time the water is pumped through it. this ill happen quickly because the engine doesn't have to heat up the fluid to get to temperature

[mad082]

if you fill the radiator up, and the thermostat has a jiggle valve in it (ar at least the whole for one, which it should) then a large amount of air will escape from inside the head before the thermostat even opens as long as you fill the radiator relatively slowly, or have the bleed screw open while filling, as this will all the air to be pushed out by the coolant so you wouldn't end up with as many pockets of air.

if you are really paranoid about it then you could leave the thermostat out (and the thermostat housing off) until coolant starts to come out of the head and then put it back on and fill up the last of the coolant and then start the car and bleed the system.

[mad082]

haha good description, but in any case the engine doesn't need coolant till it opens the thermostat, at which time the water is pumped through it. this ill happen quickly because the engine doesn't have to heat up the fluid to get to temperature

also a thermostat inside an engine with no coolant (or at least none getting to the thermostat) won't open very quickly. yes the engine will come up to temp quickly, but the thermostat won't open because the air doesn't conduct heat that well so it probably wouldn't open much at all. and then putting in cold coolant into a hot engine isn't the best idea, for the same reason you don't hose down a hot engine. the massive change in temperature can cause warping, etc. topping up hot coolant with cold coolant is ok because you are adding a small amount of cold fluid to lots of hot fluid, so by the time the cold coolant got to the motor it would already be hot.

[KrazyKong]

Picked up a new genuine Nissan thermostat today. I had a look at the Tridon/Stant ones from the auto stores and was underwhelmed. Compared with the genuine one I pulled out of my engine, these oem ones felt like toothpicks in comparison. They were half the weight and felt very flimsy. The new genuine Nissan one isn't 100% the same as my old one, but the changes are only cosmetic. It does however feel a little lighter than my original one, so am hoping it's still going to be better than the oem ones. I was half tempted to just put my old one back in as it still works fine, but the rubber seal part is starting to look a little worn so figured I'd just replace it now. The old one still has years left in it due to being very well made to begin with but I guess since I'm in this fix and replace frame of mind, bought a new one.

I'm now on Day 3 the aftermath of me trying to flush the radiator. Took me ages to get it out as I was looking for the little piece of the fan shroud that slides out. Turns out my R33 doesn't have one, thus I have to flex the shroud and 1/2 fins of the fan to get it out. Once I finally got it out, I put a pressure hose into the radiator and let her rip.

Then in all my cunning plan glory...

I decided I'd give the radiator a clean... with the pressure cleaner. So good so far... opps a few bent fins, all good I can fix them later... yep on Day 3 I'm still straightening the fins and I've only gotten one side done so far. Add to that the discovery of corrosion of some of the fins on the radiator and I'm one sad panda. The radiator should still cool fine once I'm finally done, but I'm getting to the point now where I've spend months on this car, and just want a break!

Once the radiator fins are all sorted, I'll hook it all up again with the new thermostat. I still plan to run some of that radiator flush treatment stuff through. Then it hopefully should all be good enough I don't have to worry or think about it for awhile.

[KrazyKong]

Day 4 drawing to a close and I'm in the home stretch. Quite a few more hours left until I'm done straightening the fins. I'm practically blind right now looking at the damn things for so long. My focus is all out of whack, what to speak of the headaches lol

[PhilKenSebben]

What is wrong with simply undoing the lower radiator hose and opening the top bleed screw?

Physics dictates that so long as the car is level, every drop of coolant below the bleed screw (highest point) will come out of the bottom radiator hose, both from the radiator itself and the block.

That's how I've always done it, is it wrong? Oh and make sure the heater is on to flush those lines too....

[gotRICE?]

What is wrong with simply undoing the lower radiator hose and opening the top bleed screw?

Physics dictates that so long as the car is level, every drop of coolant below the bleed screw (highest point) will come out of the bottom radiator hose, both from the radiator itself and the block.

That's how I've always done it, is it wrong? Oh and make sure the heater is on to flush those lines too....

Because where the bottom radiator hose exits the block, it isnt the lowest part of the cooling system INSIDE the block. So once the water level has drained off to the level of the bottom hose, the water below it sitting in the block just sits there. Hence the block having its own drain plug.

Here is a Michelangelo jig of what i mean.... biggest lolpaint ever but you get it..

And just incase its reall unclear.. its an asshat cross section of one cylinder

Edited June 1, 2010 by gotRICE?

[central coast person]

Yes and i forgot to do this and i am free this weekend too do so.

THERE IS A DRAIN PLUG ON THE BLOCK, USE IT. haha

gotRICE is all too right about that, your not flushing out the large heavy particles trapped at the bottom of the block.

[KrazyKong]

Well after a week of having the radiator out and having finally straightened all the fins, it was time to re-install the radiator and all hoses. All went ok, and I put some Locktite sealant stuff on the thermostat as well. Did a few drains of the radiator and was amazed at how brown the water was coming out. I was pumping in fresh clear tank water and it was quickly turning a frothing brown crappy colour.

But something that happened kind of freaked me out. I had the car idling for awhile, and topping up the fluids as well as doing the bleed valve. Now what I noticed was the top pipe going into the radiator was hot, yet the bottom one was stone cold. Now if the bottom one connects to the thermostat, and is cold to the touch, that means the thermostat isn't opening right? Wouldn't that mean the coolant/water is not being able to flow in a complete circle or cycle?

Shouldn't the bottom hose be hot too? Or is this the water that's been cooled down from the radiator and then is going back into the engine cooler. But what I don't understand is if it's cooler, then the thermostat will never open. Thus my confusion.

[central coast person]

Hmm a headgasket (once) must have blown or somthing similar so your coolant had oil contamination at one stage and it reacted like this, just like all coolan do to oil. I call in penaut butter

ERM go for a drive, when my car is running it varies between 77-81 degrees once its at temp (run ECU talk trip meter non stop, so i can monitor things like this all the time) You will have to monitor the good old temp guage. Dont stray too far from your house just incase anything starts to overheat. Try a drive and check fluid levels before worrying anymore. It should all be fine

One more important thing is when you installed the thermostat, did you make sure the jiggle valve on the thermostat was place at the top. OEM has it enscribed in the metal.

Also i recommend giving the 2 temp sensors near the top hose attached to the top end of the engine a clean. Simply get a socket and unscrew them and there should be a little brass piece protruding from under the wire and cap that measures temps. This may have some sludge on it and is worth a clean (there are 2)

[mad082]

Well after a week of having the radiator out and having finally straightened all the fins, it was time to re-install the radiator and all hoses. All went ok, and I put some Locktite sealant stuff on the thermostat as well. Did a few drains of the radiator and was amazed at how brown the water was coming out. I was pumping in fresh clear tank water and it was quickly turning a frothing brown crappy colour.

But something that happened kind of freaked me out. I had the car idling for awhile, and topping up the fluids as well as doing the bleed valve. Now what I noticed was the top pipe going into the radiator was hot, yet the bottom one was stone cold. Now if the bottom one connects to the thermostat, and is cold to the touch, that means the thermostat isn't opening right? Wouldn't that mean the coolant/water is not being able to flow in a complete circle or cycle?

Shouldn't the bottom hose be hot too? Or is this the water that's been cooled down from the radiator and then is going back into the engine cooler. But what I don't understand is if it's cooler, then the thermostat will never open. Thus my confusion.

the thermostat is in the top hose, which is the one that is hot. it is hot because the coolant has just passed through the engine and been heated up, then out past the thermostat and into the radiator. the lower/cold hose doesn't have the thermostat in it and it is cold because that is the coolant that has just been cooled by the radiator.

[KrazyKong]

the thermostat is in the top hose, which is the one that is hot. it is hot because the coolant has just passed through the engine and been heated up, then out past the thermostat and into the radiator. the lower/cold hose doesn't have the thermostat in it and it is cold because that is the coolant that has just been cooled by the radiator.

On my car the thermostat is in the bottom hose as you can see in this picture here.

So what you've just mentioned above is in contradiction to what's in my car. The hot hose (top) is the one without the thermostat, the cold hose (bottom) has the thermostat in it.

[mad082]

yeah sorry mate, my bad. i haven't owned my 33 for about 3 years now, so the old memory is getting a bit rusty

[KrazyKong]

That's alright bud. What I'm concerned about is that hose connecting to the thermostat is cold. Thus am worried is my car actually getting a full circulation of coolant, or is the coolant only flowing in and out of the top hose which is the hot one.

Can anyone feel the bottom hose on their 33 and tell me if after a drive, it's hot? Or how hot it is compared with the top hose?

[Galois]

ahh yes, thats what ive been meaning to take a pic of lol. yeah mine is the same, bottom leads to thermostat.

also, with the temp in the lower pipe, remember there isn't much mixing of the hot and cols water in the radiator, so you'll have the cold water from the radiator slowly leaving for a really long time.

doesn't the thermostat heat up as the engine metal does, and once it gets to temp lets the cold water run through? to keep it at a fairly steady temp?

[Galois]

hey kong, when i was doing my shitty flush the top hose was insanely hot, and the bottom only a little cooler, but still really hot. but that said, the engine was idling for a long time

you're temp gauge will give you a heads up well before you do any damage. what i'm wondering is how your top line could be hot while the bottom was cold? it must have been as i wrote just above, the thermostat opened and water was being pumped through the system, but hadn't been all the way through the radiator yet, so the rad had cold water entering the engine, which is why the bottom felt cold. does that explain it?

[mad082]

hey kong, when i was doing my shitty flush the top hose was insanely hot, and the bottom only a little cooler, but still really hot. but that said, the engine was idling for a long time

you're temp gauge will give you a heads up well before you do any damage. what i'm wondering is how your top line could be hot while the bottom was cold? it must have been as i wrote just above, the thermostat opened and water was being pumped through the system, but hadn't been all the way through the radiator yet, so the rad had cold water entering the engine, which is why the bottom felt cold. does that explain it?

the laws of thermodynamics (i think that is the right word, lol) explains that one. hot liquid, as with air, rises. so as the engine heats up, even with the thermostat closed, the hot coolant will rise and come out of the top hose a bit. this also means that the car keeps circulating coolant even after you turn off the car, at least until the thermostat closes. even after that you will still get a small amount of circulation.

also i had a look in the workshop manual in the section about replacing the coolant that once you are finished refilling it you run the engine until the gauge is half way (up to normal operating temp) and then you feel the lower hose. if it is warm then things are working properly. the thing to remember though is that from when the gauge gets to half way and when the car is actually full up to temp are 2 different things. the gauge can get to about normal about 10 to 15 degrees before the thermostat opens.