Overheating GU 4.2 Diesel.....a possible reason has been put to me.

Don't lets start that debate again Nudie.....

But you're right, at the moment the really hot water from the turbo is being sucked into the system before it gets a chance to cool the motor down, thereby negating the cooling effect the radiator has just had on that water.

thats a really dumb thing to do eh?

and hold on ..you started this......hahaha

No Wolfie, That's what I used to think....that some of the cooled water from the bottom hose (just before it re-enters the engine near the water pump) went thru the turbo. It made sense to me that the turbo would be fed the cooest possible water.

But NO, NO......that water in the bottom hose is NOT under pressure; it is being sucked up into the motor and therfore it makes sense that the banjo joint is actually directing water back into the system FROM the turbo, not the other way round. There is another junction where the water is coming out of the back of the block into the turbo (which I always thought was going INTO the block).

So, like I said, it seems the brilliant designers at Nissan have done a fine job of making a system whereby the coolest water is being "contaminated" with water from a 400 degree+ turbo BEFORE it evens gets a chance to get into the donk to do any cooling in there.

Goodness me, it almost seems like we're moving into the realms of quantum physics, and throw in a bit of chaos theory as well!

This is going to be a hard one to nut out on pen & paper, bit like the theory of light...... wave or particle......

However, it has been suggested that this is a tangible problem, and that there has been a tangible fix........ I reckon go with it...........

Book a Sunday morning with your spanner dude, re-plumb, drive a little bit..... drive some more...... drive lots more............. and....... hopefully.......... nail this bugger once and for all!!

Best of luck, and if it works, I reckon we all need to do a whip around for you...... you have spent sooooooo much money & time on this....lol!!

Cheers

Wolfie

Roachie, Wolfie,

Sorry to dissapoint you but no, that is not the fix, GQ's were overheating (with that engine) for years before the GU even came out did not have that pipe!!

The latest 2003 on 4.2 GU does not have that pipe (the one with the longer radiator) as the turbo is not water cooled. They still overheat though...

By all means, go for it and modify further as it may help... but don't you think that the engineers would have done all the research?

The research came to the conclusion that the engine cannot dissipate heat therefore the tuning stops at a certain point (that is why they come so detuned from factory).

Roachie, Wolfie,

Further to my previous post, the engine does not suck from that pipe, in fact the engine does not suck at all, the water pump moves the water around and does so by sucking from the block right in front of Cyl no 1, not the bottom radiator hose, it then pushes the water out to the top rad hose, as it travels through the rad and cools it is then continually being pushed through the bottom rad pipe and into the engine, in that process the turbo is getting its cool water from that pipe, the turbo hot side is on the bottom and it goes straight to the block and joins the hot water stream which is sucked by the water pump and the process is repeated.

Bugger Bill!!!

I thought you had nailed this thing.

Bugger..... bugger..... bugger....

I know...... put cold water in the radiator in the morning.

Wolfie

Hi Roachie,
Just one other thing that might be worth a thought. I read that you have fitted a " massive Radatior", did you upgrade the water pump to flow more water? The standard pump might not flow enough water through the radiator to use the benifit of the larger radiator.

Cheers Dave

Thanks Dave,
I have been considering putting in a Davies Craig electric water pump in the bottom radiator hose which I could switch on if it looks like things are heating up too much......but then people also say that if the water is circulating too fast (like it would if I totally removed the thermostat), then the water would go too fast to be able to pick up heat from the motor and it would still overheat.
That's another thing i can try later anyway, but really, since i've done the last few mods, it has not been hot enough to know for sure whether I've cured the problem, but it certainly hasn't been getting as hot as it was a month or so ago.
Cya mate
Roachie

G'day mate,
After reading some of the other responses here, I'm not so sure now about the direction of the water flow to/from the turbo; maybe I was right all along. Only way to check would be to undo the banjo joint on one end (near the top of the bottom radiator hose is the easiest to access....then start the cold motor and with my thumb over the hole where the bolt goes, see if water spits out of the banjo joint (ie: from the turbo).
Not really having any overheating problems now, but OE gauge does still move up a bit when I push hard, but then the VDO gauge is only showing about 110c, which is okay by all accounts anyway. So maybe all this "issue" has just been a result of a useless Nissan gauge alone.
Cheers
Roachie

Gday GT,
Yes mate it has the foot valve; which I must admit, I didn't know the significance of until yesterday when the Repco mechanic bloke said that I must keep the thermostat in the GU or it would just keep routing the water through the motor; not the radiator.
Thanks
Roachie

Thanks Barnray,
I will try to find a good Nissan workshop bloke. I had one here, but recently pyssed off in his GQ for WA.
Cheers mate
Roachie

Thanks for your interest and response waterpumpman.
Now you've got me wondering again......does the standard water pump have the necessary "ooomff" to be able to circulate the amount of coolant in the system; especially in my case as I have fitted a radiator which is twice the capacity of the original?
I'd be interested in more info from you; and I'm very certain others would too, as this has been an ongoing problem for quite a few of us.
I had previously thought about fitting a Davies Craig in-line water pump in the bottom radiator hose and simply manually operating this pump when I see the temp gauge getting up a bit.
What are your thoughts about that idea?
If possible, would you mind posting your ideas and comments in a new post, perhaps referring back to this post number.....the trouble being that this one is well past it's use-by date now and no-one is likely to come across it.
Thanks for your assistance.
Roachie

Well waterpumpman, you certainly have got me intrigued and I am looking forward to seeing more of what you have got to say.

I don't profess to be an expert on anything at all, but I do read a lot of stuff and try to make head from tail of it all. In that regard, I had been looking at the Davies Craig web site for info on their EWP (electric water pump). According to them, you have 3 choices of fitment of their pump.
1. Fit the pump and an electronic controller....remove the standard impeller and thermostat. The electronics would determine when the pump needed to be switched on and what voltage needed to be applied so that it would pump suficent coolant to maintain the pre-set optimum operating temperature. They claim the EWP can pump up to 80 litres/minute which I would imagine would be sufficient. They also talk about removing the belt that operates the standard water pump (assuming it does not also drive the cooling fan etc).
2. Fit the EWP with the existing standard water pump still in place. The EWP could be controlled by a thermatic switch which would switch it on when the coolant reached a pre-set temp (ie: when it starts to get too hot). I would prefer to do it this way, but rely on my own nouse to switch the pump on, having regard to the VDO temp gauge I have fitted and which I watch like a hawk.
3. You can also have the pump wired to be on permanently. This is recommeded for race cars and other very heavy use patterns etc.

I take your point about the slightly extra load on the standard water pump when the EWP is not switched on, but I still like the idea of being able to give the coolant circulation a bit of a boost.

Having said that, I still go back to what i said at the start; that I'm very interested in anything you have to contribute and your suggested solution/s.

Thanks again.

Roachie

Okay waterpumpman, you're still "teasing" me with your possible solution/s and the intrigue continues to build.
My radiator cap is certainly the highest point in my cooling system; no doubt about that. As for whether I am suffering from any cavitation or bubbling in the coolant, I have no way of knowing this......maybe if some kind/smart person would manufacture a transparent upper radiator hose a lot of these questions could be answered...hahaha
What exactly would you be proposing as a solution? You mentioned early in the piece that you had done work on new impeller design. Do you make these commercially? What is involved?
Looking forward to getting to the bottom of all this.
Cheers mate
Roachie

I read with interest!! but... what about those sports cars which have the radiator much lower than the engine block? They still work and very efficiently... although they do have a de-ariator sitting somewhere up in the suspension tower on close to the firewall. THe new 4.2 patrols have such deariator and a new radiator design and yet they still overheat...

Now I am going to tell you the story of my friend with a 4.2 TD GQ.
He tried (we as I helped him) and others as he worked in the automotive industry, everything, when I say everything it means the lot...
Radiator, electric fan, new viscous, thermostats, with without, head (new head), hoses, not sucking, bleeding etc etc...
Then he went a little further and increased the size of the water galleries inside the engine, then he got to talk to someone in Melbourne (I think) who mentioned the water pump and also a dearieator kit which is supposed to get rid of steam in certain parts of the engine.
There was a test method included in the kit which we did one afternoon, I can't remember exactly but the amount of bubbles and soda looking water was amazing.... We then replaced the water pump with this new one and its new impeller, and also the kit which took a whole afternoon to fit, the "after" test was much better not as many bubbles, but still overheating although slightly better....
He then decided to make a radical change and modify the way the water circulates (in other words he modified it to work like the new 3.0L engines and many falcons etc) which is more efficient??
That had an effect but not yet OK, his GQ was still getting hot but not as much.
I will add that everything was in perfect order, the engine performance was OK, timing was checked, the pump had been fully rebuilt and the injectors had been done etc...
The conclusion while towing a car trailer with a broken down Rangie on it from Fraser Island back to home was that if he backed off it would not overheat which makes it in his words not good enough (and I agree in a way) because up hills you can't backoff but I would be very interested to know what is that makes these engines rise temperature.
One more thing, at some point he even removed the grill, bullbar and everything to allow more airflow and the test proved to be fruitless....
In my opinion having seen many different engine designs and many engines pulled apart, this engine does not have the capacity to get rid of heat by design, the cast iron head and block don't have big enough galleries to get rid of the heat generated by the applications we use it on today, it was designed to be pulling a bus a slow speeds in a naturally aspirated form.
But I welcome other's opinions... as I am not an expert and my theory cannot be tested unless we can talk to the engineer who designed it.
Will