Coolant flow direction???

Submitted: Friday, Apr 29, 2005 at 19:28
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Had a great discussion with another EO member today (who shall remain nameless at this stage).

With all the drama about my cooling issues, the subject of coolant flow came up today......what direction does coolant flow through a normal radiator (ie: one with a top and bottom tank.....not a cross flow). I've had a life long belief that the coolant travels into the radiator via the top hose, gravitates to the bottom tank being cooled along the way and then gets sucked back up into the motor via the bottom hose by virtue of the water pump.

My good mate (still nameless at this stage) reckons it's the other way around.....the coolant goes from the radiator, out the top hose into the cylinder head, then to the block and down the bottom hose into the bottom tank and back up to the top tank.

What's the concensus amongst the experts?

Cheers

Roachie
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Reply By: Truckster (Vic) - Friday, Apr 29, 2005 at 19:30

Friday, Apr 29, 2005 at 19:30
remove your radiator hose on top, start engine, and see?
AnswerID: 108837

Follow Up By: Truckster (Vic) - Friday, Apr 29, 2005 at 19:34

Friday, Apr 29, 2005 at 19:34
.....the coolant goes from the radiator, out the top hose into the cylinder head
~~
thinkin about this way, how would a thermostat keep the water in the engine to warm it up? it would have to come into the radiator at the top. themostat opens, water passes it, into radiator.?

~~
mate who is spanner man says
"what ever comes from the water pum is the flow to the radiator"
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Follow Up By: Member - 'Lucy' - Saturday, Apr 30, 2005 at 17:46

Saturday, Apr 30, 2005 at 17:46
Truckster

The poor intellectually challenged 'spanner' that Roachie refers to is the same 'good samaritan' that provided the genset to charge your battery with in the Mauury Sunset Park soiree in March. Before it was rudely turned off that is.

Just can't believe he had such a thought, next he will be tell me the Earth really is flat and to be careful not to drive over the edge.

Actually thought he had all his marbles when I found out he drove a real 4WD -Toyota, however, I now expect him to turn up in a Nissan any day.

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Reply By: Sand Man (SA) - Friday, Apr 29, 2005 at 19:38

Friday, Apr 29, 2005 at 19:38
Here ya go roachie! In at the top, though radiator and out the bottom.

Ultraflush

Bill


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Follow Up By: Sand Man (SA) - Friday, Apr 29, 2005 at 19:41

Friday, Apr 29, 2005 at 19:41
Just click on Cooling System, Gives a schematic diagram:-)
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Follow Up By: Michael ( Moss Vale NSW) - Friday, Apr 29, 2005 at 22:06

Friday, Apr 29, 2005 at 22:06
Thats right sandman. Just rev the engine with the radiator cap off and watch the water get sucked downwards through the radiator.... Michael
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Follow Up By: Michael ( Moss Vale NSW) - Friday, Apr 29, 2005 at 22:36

Friday, Apr 29, 2005 at 22:36
Roachie, My wifes GU 4,2 td has a short crossflow radiator and very wide , standard,, 1999 model, i think some time ago you told me yours is a conventional unit, maybe why they changed them, as a stop gap till they changed them again on my gu3 to that stupid conventional bit of crap that hangs way down the same as the petrol. Do you still have in place the bash plate that runs from the bullbar backwards to the front crossmember, from memory that would stop the air going through the bottom of the bullbar slot and straight out the bottom and not having to go through the radiator. Michael
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Follow Up By: Member - Roachie (SA) - Friday, Apr 29, 2005 at 22:46

Friday, Apr 29, 2005 at 22:46
Sandman , thanks for the link....it confirms my thoughts have been right for the last 50 years!!!!

Michael, I've got an original ARB bar; the one they put the "W" cutout in the front of to take the Warn Winch solenoid box (stupid place to put it cos you can't get to it for regular servicing without removing the winch too). Anyway, it does have a steel plate underneath, which has a slit across it, bent downwards to act as a small deflector to shoot a small amount of air upwards towards the radiator. I've bolted a small piece onto it to increase the air it directs up that way. Do you think I'd be better off without the plate altogether?

Cheers blokes

Roachie
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Follow Up By: Michael ( Moss Vale NSW) - Friday, Apr 29, 2005 at 22:54

Friday, Apr 29, 2005 at 22:54
I think you are onto most of the possibilities, i ithink the plate is there for that reason, i was really thinking about the genuine steel winch, but i think they are made by ARB and are very similar although probably made to Nissans plans and spec.. , I think the plate should be in place, Anyway just keep on plugging away. There is obviously a cause for the problem.. Michael
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Follow Up By: Michael ( Moss Vale NSW) - Friday, Apr 29, 2005 at 23:01

Friday, Apr 29, 2005 at 23:01
Roachie, what about winter and load,, same thing or just summer. What oil do you use, Genuine nissan Multigrade. ,or a heavier oil(non multigrade) may be a silly question but we'll keep on throwing them at you.. Michael
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Reply By: Member - Roachie (SA) - Friday, Apr 29, 2005 at 19:41

Friday, Apr 29, 2005 at 19:41
Trucky,
I should have added that my belief was confirmed as far as I was concerned, when I read the directions on Davies Craig 's website for the electric water pump. Thsi device goes into the bottom radiator hose. The instructions (which can be found on their website) state that the pump, which is marked "IN" and "OUT" on the respective ports, must have it's "IN" port attached to the bottom radiator tank and the "OUT" port connected to the motor.
Cya mate
Roachie
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Follow Up By: Truckster (Vic) - Friday, Apr 29, 2005 at 19:44

Friday, Apr 29, 2005 at 19:44
talkin with a spanner man mate, have you checked for cracked head recently?
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Follow Up By: Exploder - Friday, Apr 29, 2005 at 20:32

Friday, Apr 29, 2005 at 20:32
Yep have to agree with Roachie on that one depending on manufacturer thou.

Simple to find out thou just take the cap off have the water level a little low make sure it is hot enough for the thermo to be open and get some one to rev the engine and see which way the water flow’s.

As to how would the thermo keep the water in if it came from the bottom up simple just think of it as a pressure relief valve activated by heat , another test is just have the car idling in the driveway and see which hose gets hotter faster.

Down at a mates farm we have a old Ferguson tractor that we fixed up, when we put the cooling system back together we accidentally left the thermo out . This thing you can run for like half a day take the rad cap off and the water is hardly even hot. Now that is a cooling system and the water runs up thru the engine and comes out the top

Have you tried running it without the thermo in?
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Follow Up By: Member - Roachie (SA) - Friday, Apr 29, 2005 at 20:57

Friday, Apr 29, 2005 at 20:57
Truckster, No water in the oil, so I don't think the head is cracked. No other symptoms either. No bubbles in the coolant.

Exploder, I posted a question a week or 2 ago about what possible problems I might cause myself if I run the engine without a thermostat. The vast majority of people who responded said NO WAY.....the coolant will pass through the motor too quick and not get a chance to pick-up the heat from the motor and also too quick to lose the heat in the radiator as it won't spend enough time in it. Seemed a bit funny to me but there's no way I'm gunna knock anybody else's ideas, so I just soak it all up and try to work out which way to jump once I have lots of opinions. That's the great part about this site.

Cya mate

Roachie
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Follow Up By: Truckster (Vic) - Friday, Apr 29, 2005 at 22:16

Friday, Apr 29, 2005 at 22:16
No water in the oil, so I don't think the head is cracked. No other symptoms either. No bubbles in the coolant.

So I take it as a no? You still could have a cracked head.
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Follow Up By: Truckster (Vic) - Friday, Apr 29, 2005 at 22:20

Friday, Apr 29, 2005 at 22:20
PS... so in the top of radiator from the head and out the bottom into engine is correct.
[ View Image]
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Follow Up By: Michael ( Moss Vale NSW) - Friday, Apr 29, 2005 at 22:22

Friday, Apr 29, 2005 at 22:22
Roachie, i dont think leaving the thermostat out always makes the engine run hotter, i used to do it years ago and i would have to put it back in for winter just to get the heater going. It may be the case on some engines but i have never experienced this. What it will do if you run the engine cold, especially a petrol engine is cost you horsepower and fuel, as the engine is more efficient running at hottest as practical.
I dont even think a lower temp thermostat will fix as the problems only occur at high load. Maybe is bull bar related, where is your number plate, why not relocate to one side, maybe in the way, just adding to the lights and winch. it really is a tough one... michael
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Follow Up By: Truckster (Vic) - Friday, Apr 29, 2005 at 22:34

Friday, Apr 29, 2005 at 22:34
Dumb question #4.4a

Have you had it back to nissan for them to check it all out?
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Reply By: Lone Wolf - Friday, Apr 29, 2005 at 19:58

Friday, Apr 29, 2005 at 19:58
Any water pump I've had to replace, the impeller sits inside the block, therefore impelling water out to the outside of the pump, into the top hose.

Cracked head??? Just look at the bubbles coming in from the top hose.

Wolfie
AnswerID: 108845

Follow Up By: Member - Pesty (SA) - Saturday, Apr 30, 2005 at 10:37

Saturday, Apr 30, 2005 at 10:37
Hi Wolfie,
The pump doesnt connect to top hose? and I have never thought much about it nor ever tried it as i dont get much overheating problems and when i have its an obvious problem.
The theory I used as i have had a lot to do with impeller pumps as part of my work is that they suck in to centre of impeller and force out the outer edge but they are working backwards if this is the way of the cooling system, unusual way for impeller pump to work
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Reply By: Member - Davoe (WA) - Friday, Apr 29, 2005 at 20:02

Friday, Apr 29, 2005 at 20:02
you remove the radiator turn it upside doen to back flush it so you work it out
AnswerID: 108846

Follow Up By: Member - Matt Mu (Perth-WA) - Monday, May 02, 2005 at 14:18

Monday, May 02, 2005 at 14:18
Davoe is absolutely correct...you back flush to remove deposits and scum. Bottom to top in a radiator and you remove the thermostat and flush from top to bottom (against the normal flow) in the engine.

The engine could (theoretically) operate without a water pump..its called thermosyphon. The water as it cools sinks and rises as it is heated. So in the radiator, the hot water enters the top tank and sinks to the bottom as it cools, while the engine received cool water at the bottom and as it heats it rises up to the head ands out the thermostat.

Also be carefull of removing thermostats to solve engine running temp probs....thats a VERY old trick and not relevant today in our engines.

There is a need for the engine to reach its OPTIMAL running temp (controlled by thermostat) anything less or more and its emissions (fuel consumption) and power are all overthe place.

Also some new modern engines thermostats have two jobs when they operate, one to open the valve to the top hose (standard) another to close the bypass loop in the engines quick warmup flow. If removed this loop isnt closed and hot water from the engine can continuously flow around the engine without having to flow to the radiator for cooling.

Lastly the thermostat is needed for a restriction in the flow of water to allow the time needed for the water to absorb the heat. Otherwise the water can pass too quickly without absorbing the heat from the engine its trying to cool!!

I know these cooling issues are a pain in the backside, but I have found and been quoted (cooling specialists, for what its worth)that as small as 15% restriction in airflow through the radiator can cause overheating of engines. So when you remove the standard bumper with its good airflow, fit a large bullbar (poor flow) and then block the air even more with driving lights and winches, winch control boxes, bug screens etc.....

What hope do they have?

Matt.
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Reply By: Sand Man (SA) - Friday, Apr 29, 2005 at 21:30

Friday, Apr 29, 2005 at 21:30
Bill,

The "Ultraflush" site I mentioned above gives a good description of how the various components of the Cooling System work.

Just click on Ultraflush above and then click the Cooling System icon. As well as the description, the diagram shows quite clearly via directional arrows, that water falls down, not up:-)

Bill


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Follow Up By: Lone Wolf - Friday, Apr 29, 2005 at 21:50

Friday, Apr 29, 2005 at 21:50
"Ultraflush...."

Reminds me when I was a bit younger, and still as silly.

We wanted to make a quick bong, and we used an Ultrafresh bottle, called it Ultra Bong.

The best one we ever had was an old BP oil container ( 500 mm), we called that one the quiet achiever!

Wolfie
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Follow Up By: Sand Man (SA) - Friday, Apr 29, 2005 at 22:25

Friday, Apr 29, 2005 at 22:25
Have another Bourbon Ian:-)
Bill


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Follow Up By: Michael ( Moss Vale NSW) - Friday, Apr 29, 2005 at 22:41

Friday, Apr 29, 2005 at 22:41
Sand Man,, bad advice,,, thats the problem LOL
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Reply By: ianmc - Saturday, Apr 30, 2005 at 01:09

Saturday, Apr 30, 2005 at 01:09
This all sounds like the ole fan blade debate to me!
Maybe the water runs uphill in the southern hemisphere & downhill in the northern hemisphere where they dont have to stand upside down.
Or is it the other way about! Gee its 1.08am, I must get a life.LOL
AnswerID: 108887

Reply By: Member - toohey - Saturday, Apr 30, 2005 at 11:43

Saturday, Apr 30, 2005 at 11:43
gid'ay all
have just changed coolant in 3.0lt.nissan,did temp. check,flows to radiator from top hose.
regards toohey.
AnswerID: 108919

Reply By: Member - Bradley- Saturday, Apr 30, 2005 at 15:07

Saturday, Apr 30, 2005 at 15:07
there was a bloke in melb making reverse flow systems a few years back ,using divertor blocks and valving etc. reconed it made the temps more stable etc. smoother running etc etc. Havent heard anything new on it for a few years though so it may have folded.

Another suggestion, have you tried shimming up the rear of the bonnet to give a small gap for the hot air to escape easier ?? old trick that can work well..
AnswerID: 108935

Reply By: Nudenut - Saturday, Apr 30, 2005 at 20:36

Saturday, Apr 30, 2005 at 20:36
why would it go the other way..who was the jerk that says it goes in the bottom and out the top....

heat rises and vice versa for cold....one would want the cooled coolant to drop and not fight the laws of of of...... whatever the law is
AnswerID: 108990

Follow Up By: Lone Wolf - Saturday, Apr 30, 2005 at 21:50

Saturday, Apr 30, 2005 at 21:50
It's called the laws of coldness, and Tracy makes sure I am aware of them....lol!!

Wolfie
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Reply By: AndrewX - Saturday, Apr 30, 2005 at 21:34

Saturday, Apr 30, 2005 at 21:34
Oh boy how can it be that so many people know so little about the basics of cooling an engine and the purpose of a thermostat and water pump? Roachie .... the fact that you even considered that your mate might be right tells me that you have no hope of solving your overheating problems unless you find someone that understands the basics of engine cooling.
AnswerID: 109001

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