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Thread: Coolant is still running too cold?

  1. #51
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    Quote Originally Posted by dom14 View Post
    Yeah mate. You were right about T pieces being there for a reason. And I was wrong about heater core coolant entry having a four way valve as above anyway. I've corrected that in a post after that, and I'm just about to post all the details, pictures from the factory manual and Gregory's manual about it.
    T joints were put there 'cos there's no other way to do it. Series setup would've cut the coolant flow to LPG converter or heater core or both depending on which one I plumb the coolant entry first. When the tap inside the heater core is shut by sliding the dashboard heater slider to cold, that will cut the coolant flow completely, which won't be a good thing for the LPG converter to start with.(and may even create cavitation air bubbles on the coolant return line to the engine block, which would "help" to create cracks in the cylinder head in no time, so it's definitely a bad idea)

    I will replace the thermostat with a brand new stock one (76 degrees) to start with and see how it goes, 'cos the current one is opening up at around 70 degrees or bit less, which I think the major reason for low temperature. If the new one still yields low temperature then I will install a one bit higher, like 80 degrees or so.

    I will also replace T pieces with Y pieces soon. I've been told it's better for the flow and helps reduce cavitation(air bubbles inside coolant).

    Cheers
    Dom
    Forget about installing a thermostat with a temp you think may be the right temp setting.
    Ask Mr Nissan for a thermostat to suit your vehicle VIN number.
    Then ask him what'c the temp setting that's stamped on it?.
    Don't quote me, I believe the Gen p/No is 2120042L01W and about $45.

    Cavitation from a t piece--- doubt it.
    The Y would reduce back pressure for sure, just insure you get the flow direction correct.
    that is the stem feeds the y on the hot side too heater and lpg mixer
    and the y part feeds back from the heater and lpg mixer to the stem on return .
    I tried Y's on GQtb42 lpg, didn't see any difference at the gauge , you may get a deg or two difference if you spend $20 per joint on a Y.
    Then again it may allow the water to flow to fast through the lpg and heater cores to allow sufficient time for more heat transfer who knows!.
    The speed of flow needs to be just right to allow time to cool off, to fast and water retains more heat.
    Again this gets back to the job of the thermostat helping to control flow.
    See how you go with the thermostat first hay. cheers.
    IF IT'S NOT A NISSAN.
    THEN IT'S A COMPROMISE

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    dom14 (24th August 2016)

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  4. #52
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    Quote Originally Posted by Robo View Post
    Forget about installing a thermostat with a temp you think may be the right temp setting.
    Ask Mr Nissan for a thermostat to suit your vehicle VIN number.
    Then ask him what'c the temp setting that's stamped on it?.
    Don't quote me, I believe the Gen p/No is 2120042L01W and about $45.

    Cavitation from a t piece--- doubt it.
    The Y would reduce back pressure for sure, just insure you get the flow direction correct.
    that is the stem feeds the y on the hot side too heater and lpg mixer
    and the y part feeds back from the heater and lpg mixer to the stem on return .
    I tried Y's on GQtb42 lpg, didn't see any difference at the gauge , you may get a deg or two difference if you spend $20 per joint on a Y.
    Then again it may allow the water to flow to fast through the lpg and heater cores to allow sufficient time for more heat transfer who knows!.
    The speed of flow needs to be just right to allow time to cool off, to fast and water retains more heat.
    Again this gets back to the job of the thermostat helping to control flow.

    See how you go with the thermostat first hay. cheers.
    Cool, thanx mate.
    Yeah, I'm not too fussy about Y pieces, but I bought them while ago and it's somewhere in the stash of crap.
    The reason I didn't install them 'cos Y's are bit cumbersome, comparing to T's.
    They are obviously bit better for the flow. Cavitation thing is a suggestion by a forum member. So, I went by that advice.

    I think my rig's been running low temp for a quite a while without me noticing it.
    I'm guessing the excess blow by is probably from that, causing bit of extra wear on piston rings or so.

    Thanx for emphasizing the importance of the flow speed above mate. I now know the engine cooling system is far more complicated than I would like to believe. I still understand very little of it, but at least I'm aware of my ignorance now, so I won't muck around with it without doing the due homework. . It's good to know that i don't know. . We usually end up in trouble when we don't know that we don't know.

    Cheers
    Dom
    Last edited by dom14; 24th August 2016 at 02:36 PM.
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  5. #53
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    I'm no expert by any means, picked up on a few bits over the yrs and trying to help out if I can, do unto others.
    Hate to see someone having trouble, we've all been there hay.
    And yes the Y's take up a bit more room than the tee's for sure.
    IF IT'S NOT A NISSAN.
    THEN IT'S A COMPROMISE

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    dom14 (26th August 2016)

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    I just discovered the coolant flow direction that I sketched in the diagram earlier was NOT correct between the heater core and engine block. The ancillary coolant port next to the thermostat on the engine block actually receives water from the heater core(not sending water out of it). I've corrected the final diagram as below.
    I will also move the sensor from front ancillary hose port to the back ancillary hose port of the engine block, and see whether it can yield a slightly higher temperature reading. Logic says it should, as the current spot at the return line of the heater core should be slightly cooler. I will update the outcome soon.

    These are the final and accurate diagram(s) of RB30 Patrol coolant flow. The second one is taken out of R31 Skyline(RB30 engine) coolant flow diagram and slightly modified to suit RB30 Patrol(carby) engine. Previous diagrams in the previous posts of this thread were already corrected to reflect below diagrams.
    Last edited by dom14; 2nd September 2016 at 12:28 AM.
    RB30, some 2-3 inch lift auxiliary LPG tanks
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    Forever impressed by your work @dom14. Your diagrams make life much easier to visualize things.

    Also, tried messaging you back, but your inbox is full

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    dom14 (2nd September 2016)

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    Quote Originally Posted by Throbbinhood View Post
    Forever impressed by your work @dom14. Your diagrams make life much easier to visualize things.

    Also, tried messaging you back, but your inbox is full
    Yeah, mate. Just been busy "upto my arse". Need to do bit of housekeeping with my email box. Cheers.

    P.S. It's not easy, 'cos most of the email, if not all, are really important communication with members. , I just have to forward them to another email box or something.
    Last edited by dom14; 2nd September 2016 at 03:30 PM.
    RB30, some 2-3 inch lift auxiliary LPG tanks
    Few more mods on the way
    http://www.worldwildlife.org/species/tiger
    https://www.panthera.org/
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    Coolant system Myths

    I picked below said coolant myths from an article on the web.

    Coolant can be pumped too fast through the engine for it to absorb enough heat, or
    Coolant can be pumped too fast through the radiator for it to cool properly, or
    Cooling can be improved by slowing the flow of coolant through the radiator so it cools more completely.


    The detailed article that explains why the above are myth is below.
    http://www.pirate4x4.com/tech/billavista/Cooling/


    Relevant part from the long article above, that relate to the myths above, is below.


    Myths

    For those that cling tenaciously to myths, I am going to take one last crack at forever dispelling the Granddaddy of them all when it comes to cooling systems.

    The myth is stated as either:

    Coolant can be pumped too fast through the engine for it to absorb enough heat, or
    Coolant can be pumped too fast through the radiator for it to cool properly, or
    Cooling can be improved by slowing the flow of coolant through the radiator so it cools more completely.
    NONE of these is true. The simple truth is that higher coolant flow will ALWAYS result in higher heat transfer and improved cooling system performance.

    The reason the myth is so persistent, is that: a) without knowledge of fluid dynamics and laws of thermal conduction it does make a kind of intuitive sense and b) it is based on a tiny kernel of truth, but that kernel of truth does not explain the overall system behaviour and so, interpreted out of context, leads to a completely erroneous conclusion.

    So, let's start with the tiny nugget of truth. If you had a sealed rad (no flow) full of hot coolant, and subjected that rad to airflow, yes, the longer you left the coolant in the rad, the more it would cool. However, if you were to plot that cooling over time, you would find that the RATE at which the cooling takes place is an exponential curve that decreases with the temperature difference between the hot coolant and the air. Put another way - when the temperature difference (delta-T) between the hot coolant and the airflow is large, heat transfer (cooling) initially takes place very, very quickly (almost instantaneously). But as that happens, and the coolant cools, the delta-T becomes less, and the RATE at which further cooling happens gets less and less until the point where the coolant and air are almost the same temperature and continued cooling takes a very long time. This is Newton's law of cooling. To illustrate this, recall my "quenching steel in a bucket" analogy.

    A good example of this law can be seen when quenching a red-hot piece of steel in a bucket of water. At first, the temperature difference (delta-T) between the red-hot steel and the water is huge - therefore the initial heat transfer occurs at a great rate - the steel initially cools very fast - almost instantaneously. However, after this initial cooling, the delta-T is much smaller, so the remaining cooling occurs much more slowly. If you removed the steel after a second or two - it has cooled a lot - but it will still be warm. To continue cooling the steel to the temp. of the water, you have to leave it in there quite a bit longer - because as it cools - the rate of cooling continually decreases as well. In short - initial cooling is fast, but subsequent cooling occurs more and more slowly until cooling that last little bit takes a long time.

    So what does this mean? Basically it means, the longer the coolant stays in the rad, the less efficient the cooling that takes place is - to the point that the rate of cooling is so slow as to be detrimental to overall system cooling. Better to dump the big load of heat right away and go back quickly for another load than hang about waiting for a last little bit of insignificant cooling to happen.

    To understand fully, we have to put our rad back into the whole system where coolant is flowing and consider the effects of flow rate on the system as a whole.

    Slowing the coolant in the rad may allow that coolant (the coolant in the rad) to dissipate a little more heat (but not much), and at an ever decreasing rate (exponentially decreasing) BUT since the cooling system is a closed-loop system, you also have to consider what’s happening outside the radiator if you slow the flow - especially to the coolant in the engine. If you slow the coolant through the rad, you slow the coolant through the engine too. And this coolant is subject to the same laws - the greater the initial temperature difference between the engine and the coolant, the greater the rate at which the coolant absorbs the heat from the engine. BUT - if we leave the coolant in contact with the engine for longer by slowing the flow through the rad, the delta-T between engine and coolant decreases and with it the rate at which the coolant in the engine absorbs the heat from the engine. Meanwhile the engine is banging away producing heat, but the coolant is absorbing it at a slower and slower rate - that heat has to go somewhere, and since the slow coolant is becoming less efficient at absorbing it - it stays in the metal - and the metal overheats!

    Meanwhile, back at the rad, you're wasting time trying to shed the last little bit of heat when the delta is small instead of carrying away the “big chunks” of heat. And the situation just gets worse and worse in a downward spiral.

    Imagine emptying a truckload of sand using a small wide-mouth container vs. a larger narrow-mouth container. The job will get done quicker by making more trips with the smaller container that takes less time to fill and empty, rather than taking the time to fill the larger narrow-mouth container and then taking the time to empty it – that extra in the larger narrow-mouth container isn’t worth it – better to dump the load and go back for more.

    Or, how about this for those who are fans of elaborate metaphors
    Imagine a circular train track with two stations opposite each other and rail cars that fill the whole track. One station has an endless supply of passengers trying to get on and the other is where they get off and disperse. Your job as the train driver is to move as many people as possible to keep them from accumulating at the embarkation station and crushing each other. Now imagine the passenger cars are funnel-shaped on the inside. This means the first big batch of people can get on and off quickly, but completely filling the car takes a lot longer as people have to squeeze into the narrower portion.
    So, you could drive the train slowly, only moving along after each car has completely filled and completely emptied… but efficiency will be greatly reduced as it takes so long to get those last few people on or off the car – meanwhile the never ending supply of people at the embarkation station never stops and the system backs up and the people get crushed because, even though more people get on or off each car, the whole system is less efficient.


    OR

    You could drive the train fast, quickly loading and unloading the big, easy-to-fill, portion of each car, forget about the smaller portion, and keep picking up and dumping off a large group of passengers as fast as you can. In fact – the faster you go, the better…the more efficient at moving large numbers of people the system will be. Screw the last stragglers – they’re insignificant and won’t help you – just move the big chunk and move on, going back for more, more often.

    So – you want high flow / high (turbulent) speed so it picks up and dumps off the most heat quickly – it’s inefficient to try and shed the last little bit of heat when the delta is small, and can lead to overheating because you’re wasting time not carrying away the “big chunks” of heat.
    Last edited by dom14; 9th September 2016 at 12:37 AM.
    RB30, some 2-3 inch lift auxiliary LPG tanks
    Few more mods on the way
    http://www.worldwildlife.org/species/tiger
    https://www.panthera.org/
    Cheetah Outreach

  12. #58
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    m2cw.
    Real world , were ambient air temp varies, vehicle speed , air flow speed through rad varies, then also factor in- head wind, up hill etc.
    We still need the system to operate as it was designed to, or have extra capacity to compensate for any increases in thermal load placed upon it from load & or worked engine etc.
    Some may think a std rad is up to the task, that's only due to some extra capacity factored in for hot weather (real world) & to prevent warranty claims, no-one buys cars new that overheat easily.
    And a given, the thermostat needs to be working correctly.

    So how are the temps going in your's now?.
    IF IT'S NOT A NISSAN.
    THEN IT'S A COMPROMISE

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    dom14 (7th September 2016)

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    I haven't had a chance to test it yet, but I moved the temperature sensor into the coolant port on the rear of the block.

    I'm dealing with ways to cut down blowby atm.
    I'm making a catch can setup( a home made cheap one) to start with and monitor oil mist output.
    Actually, I'm thinking two catch cans for each breather out of the rocker cover and plumb then into the PCV input & air cleaner, the way it's connected in the factory setting.
    I'll open a different thread on that as well.
    If it works, then I can consider buying a proper aftermarket catch can.

    I'll post the outcome of the thermostat & temperature reading soon.
    The engine's definitely running tad cooler, and the thermostat is definitely the biggest contributor to the 'problem'.
    I guess running closer to 70 degrees may not be that bad during warmer months as it may run bit hotter as it's coming to Spring and Summer now. I'm more worried about engine's not reaching it's temperature quickly enough.
    The most of the condensation buildup under the rocker cover(near the oil filler cap) is I think from engine oil NOT getting hot enough to vaporize the moisture.
    I think, if I can get the engine to reach the operating temperature quickly enough and maintain the temperature around 80 degrees celisus or so, then I would be happy.

    Yeah, it makes sense to me that there is such thing as "coolant can flow too fast" through the coolant system, 'cos if not temperature, the pressure will be affected(which may be a bad or good thing, depend on each situation).
    One thing is obvious though. Coolant system is far more complicated than it looks, and lot of "hard physics" go into making them.

    It's definitely a pretty complicated subject.(namely the "heat management").

    I mentioned in a lengthy post above that "pouring cold water into an overheated engine" is a bad idea and the best we can is to stop the engine and let it cool down normally, 'cos pouring cold water, especially too much cold water can cause the overheated head and block to crack by sudden drop of temperature. I also heard literature against that, saying the temperature of the head and block even rises more as soon as we stop the engine(because whatever the left of the coolant stops flowing).

    But, I think that temperature rise does minimal damage 'cos

    1)It will be for a very short period
    2)It's a far cry from stopping the engine and then pouring lot of cold water into the engine which has a lot higher probability of damaging the engine.

    I think, one thing we can do is to open the radiator cap(if it can be opened safely), and pour water a little bit at a time and run the engine to keep the coolant flowing. But, that can be way too dangerous.
    Opening an overheated radiator cap with hot steam in it ain't a good idea, regardless of any safety precautions that we can take.

    Best thing we can do is to stop the overheated engine and let it cool down by itself, IMO.
    Last edited by dom14; 7th September 2016 at 02:43 PM.
    RB30, some 2-3 inch lift auxiliary LPG tanks
    Few more mods on the way
    http://www.worldwildlife.org/species/tiger
    https://www.panthera.org/
    Cheetah Outreach

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    Just out of curiosity, your viscous hub isn't locked on or anything like that is it?

    Also, does your thermostat have a little bypass nipple on it? I know this is a weird question, and my rb30 has the nipple on it and runs 78-82. But when chasing an issue with my xr6turbo where it simply wouldn't heat up quickly, and would cool down on long freeway stretches (to the point the heater was cold). Turned out to that it had one of those nipple holes in it for some reason. Put one without the nipple thing and it's been perfect since.

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