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Discussion Starter #21
Ok, my 4.2 has (2) inlets on the top of the water pump in addition to the lower main inlet. The inlet on the left is the where the return from the heater core pipe goes. The one to the right if standing in front of the vehicle has a threaded plug and I've been reading that this one is required for some type of bypass if using the V-belt design as opposed to serpentine belt setup. Why that matters I have no idea.
Also, the verdict as I suspected is that the radiator is good. I went and picked it up from the repair shop today. They cleaned it up real nice but tell me its good. The other spare radiator that I took in failed.. So I know I have a good radiator, a new water pump, block test is good, new thermostat and it functions correctly. I can't find any blockages anywhere and have double checked. So its down to either airflow or again some type of incorrect plumbing.

Ive never had one be so difficult.
So I am trying to figure out this potential issue with the potential need to have a bypass hooked up in some way to this second inlet that is supposedly required for v-belt 4.2

So again, Im all ears on some additional areas to look at.


thanks
 

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My 3.9 runs with the right hand waterpump spigot (looking from front of vehicle) blanked.

The small hose return from the top most point ( intake heat circuit) goes to the left hand of the two radiator pipes (most extreme left of the two looking from front of vehicle) which I believe is critical in scavenging any airlock from the highest point of the motor.
The carburettor fed type prior to fuel injection also did this from the top most point of their manifold.

Look inside the radiator via the fill plug, there is normally a difference between the two small bore pipes. One with an extension pipe internally and one without, what is your one arranged like in there?
 

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Just an additional consideration, the hoses and circuit through the intake throttle warming circuit have been verified as clean and with clear flow?

It won't self bleed without the above, with air lock an inevitable consequence.
 

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1989 Range Rover Classic
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My configuration (v-belt) has the left port blanked as well (I actually hadn't even noticed there was a second one until I looked more closely). In terms of ensuring the throttle body circuit is clear, you should be able to remove the radiator cap directly above those lines (when starting from cold) and see coolant flowing out of the line coming from the throttle body.
 

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Discussion Starter #25
Ok, so it sounds like I'm fine running with one of the small upper water pump inlets being blocked off so I am going rule out having it blocked off as a potential issue.. I did check for obstructions for the throttle body heater and found none. I can see coolant flowing out of those lines. I even bypassed the heater by connecting the hoses and still eventually was overheating. Now, as far a radiator, I am running a discovery 2 radiator which is a bit different than the older 93 4.2 radiator. Discovery radiator only has the main inlet and main outlet and only has a small hose barb at the very top right for the bypass, air to escape back to the expansion tank cap. This is why I asking on confirmation for some of the connections from the throttle heater and where they terminate as I know your radiators have the 2 hose barbs on the left side to catch air pockets.

For the throttle heater, I have the one small hose coming off the intake that feeds the heater. Then I have the heater return line running across the motor to the bottom of the expansion tank as is proper set up for a Discovery 2. Whereas this same return throttle heater hose on the RRC goes directly to the top of the radiator on the left side of the radiator standing in front of the vehicle. Perhaps, I am getting airlock because this return is going to the bottom of the expansion tank that is normally full of liquid? I supposed I can splice a tee and tap into the bypass that is on the top of the radiator that runs over to the cap for the expansion tank. This way the return would free flow dump into the radiator or spit out thru the expansion cap dumping back into the expansion tank. Right now, as set up going to the bottom of the expansion tank since does not appear to be much pressure or flow, I can see it air locking or having trouble trying to fill a pressurized expansion tank from the bottom where coolant is already present.

I'm also doing a patch up fab job creating a bit of a makeshift shroud for the electric fan. If anything it should give it better airflow. I am hoping that the rerouting of the throttle heater hose solves the problem though.
I'll keep you posted!
 

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Just looked inside a radiator with two spigot fitted.

The left most one (outer most) is routed internally with a small pipe across to the front of the radiator cavity, this is the one my plenum return is routed to.

The other one ( innermost) and routed from radiator to expansion tank, just enters the cavity flush.

They are both in the same chamber so I can't see there's going to be a pressure difference, but not obvious why they are separated.
 

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1989 Range Rover Classic
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Just looked inside a radiator with two spigot fitted.

The left most one (outer most) is routed internally with a small pipe across to the front of the radiator cavity, this is the one my plenum return is routed to.

The other one ( innermost) and routed from radiator to expansion tank, just enters the cavity flush.

They are both in the same chamber so I can't see there's going to be a pressure difference, but not obvious why they are separated.
Your hoses cross? Outer one to the plenum and inner one to the expansion tank? That's interesting, mine is the other way around.

EDIT: Well after perusing google images, mine might be backwards!!!
 

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1970-1995 Range Rover Classic
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@RodgerD -

Please PM me - happy to connect and send a video or, snap photos of the hose routing.

I have a 95 RRC with a 4.6L block - this should be very similar to your hose/radiator setup sans electric fan.

Still believe your issue is airflow..... :)

Thanks,

Chris
 

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Discussion Starter #30
Chris, Lance, definitely looking more like airflow issues as you suggest. I ending up sourcing a hi-flow windstar fan from a salvage yard a few days ago after I confirmed the radiator was good. I spent about an hour today modifying the shroud to fit the Discovery radiator. I then replumbed, bled, hard wired the fan on and started it up and noticed some immediate improvements. It did not overheat at all on idle and even when the thermostat opened the lower radiator hose remained cool which with the old 12" fan the lower radiator hose was very hot. I didn't have time to get it on the road today so tomorrow I'll do a road test and hopefully she will not lose her cool because I am about too!! thanks again for all the help especially confirming some of the hose connections because I am running a bit of a frankenstein.
 

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Discussion Starter #31
Ok, I'm about at my wits end with this thing. Basically the same thing its still overheats under load. this running the electric fan constantly. Doesn't take too long driving. I think that the temperature fan switch that goes on the elbow to the thermostat is bad. I replaced the other coolant temp sensor. Im not familiar with 14CUX could a fault in the fan switch be forcing injection system to run lean which could cause an overheat? Im fresh out of ideas on this one.
 

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Swap to the original viscous setup if you have the components as a test.

Also, the sender for the gauge could be faulty - but if it was working properly previously it is unlikely.

Temp creep under load is classic for low air volume. Not sure where you are located... I am north of Atlanta, Ga.

We have the same radiator - I would not run a single electric fan of any size in our summer heat.

I am still running the VC fan with no issues - it is a power drag, and is loud, but it works. However, considering a dual fan setup once I upgrade the alternator to 100 amps to eliminate the drag and noise.
 

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Discussion Starter #34
Thanks all, I have just the viscous fan but not the shroud for it so I guess I'll start trying to source one of those. To try and bring it ask to stock setup as possible. I am running the #1 temp sensor for the gauge. However I haven't even bothered to hook it up to the D2 Cluster at least not yet anyway. I was looking at getting an aftermarket triple gauge set to hook up in conjunction with D2 Cluster.

I do think that this switch is bad... as it seems to be grounded and fan runs all the time.. Thats why I was wondering if that could be having the 14CUX run the motor lean causing an overheat.


Airflow issues, Im not sure anymore. That new fan on there seriously pulls air thru the shroud and all the time and still overheating. I just dont get it as with the old 4.6 it was running the viscous setup on the same radiator and zero problems and it didnt seem to pull nearly the air like this new setup.

I'm going to source a shroud, get an aftermarket temp gauge kit, and new thermostat fan switch on order. Uggh, what a pain this one has been.
 

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The fan switch should default to on, and run the fans when it fails - so it is likely bad.

On the 14CUX, the only temp related channel that it listens to is linked to the the temp sensor that is directly in front of the gauge sender on the 4.2l.

My understanding it fattens the mixture for cold start only. Someone please correct me, as it has been quite a bit since I reviewed this information.
 

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I've got it the same as you Lockettc, just enrichment for cold start in a gradient as temp sensor ramps resistance up and down for that report channel.

The original fan running on pulley is not to be underestimated though. My understanding of that is it can be consuming, at peak, 5 to 7 bhp. That's an awful lot of suck through! taking some hefty electric "fannage" to cover off that performance, especially at high ambient conditions.

Don't forget, you've got thermostat control for water and viscous bite point BOTH working to ramp up cooling as temperatures come up too.
 

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As I mentioned before, if it overheats at speed, its a coolant flow/radiator issue, not airflow. Yes the big viscous fan moves some air, but it's next to nothing compared to the flow of air moving through when driving at 60-70mph. Open the hood and feel the flow from the viscous fan when hot (rev it a bit too), then stick your hand out the window flat into the air stream at 70mph and you'll realize how insignificant the fan is at high speed. Fans are there for low speed and idle. If it's overheating under load at speed, something in the cooling system isn't up to snuff, be it flow through the water pump, the capacity of the radiator, or an air bubble. This is still an issue at idle, but it takes a lot longer to heat up as it's not under load. What does the IR thermometer tell you at the water neck and the bottom radiator hose when it gets warm?
 

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Discussion Starter #38
Hi guys has been a busy couple of days. Lance I am with you, it just seems to be more of a coolant flow issue. That Windstar fan blows some serious air and it just should not overheat like that when driving. The radiator as I suspected was good... as the 4.6 it never had an issue. So the issue seems to be more related to the new to me 4.2. With a new water pump and even removing the thermostat motor was still overheating. I went thru and removed all the external hoses and blew them out and flow is good thru the both the heater core and the plenum heater. My gut is now leading me to suspect that perhaps when this top end was done either the intake manifold gaskets are leaking internal or maybe head gasket. Somewhere something just doesn't seem to be getting the flow of coolant that it needs. Perhaps its a air bubble. I'm going to have to look at it some more is there some type of secret because I've done except put a vacuum pump on it. Take the caps of the downspout and the expansion tank, start it up fill, cool off repeat. Even squeezing hoses... If you think it needs a vacuum pump to be sure I guess I'll look into that before I start tearing into the top end. What a pain.
 

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Reading through this and having had to address overheating on my 'Barn Find' 1983, I do think your issue is the radiator. You say it has been tested but what does that mean? It might flow and not leak but does it exchange heat effectively to the air?

My engine slowly but surely overheated. I too started looking at hose routing, air pockets, thermostat, fans you name it.I changed the pump as it started to leak and found the old pump to be prefect and the new pump not making any difference. I had the original copper radiator which looked great (car had 37k genuine miles). Was considering having it refurbished but found that this service does not really exist anymore. I flushed it but found it was clean inside (bore scope). Still overheating issues. After a bit too aggressive a cleaning solution it started to weep on one of the solders and I decided to just proceed with a new aluminum radiator.

The difference was instant! Never ever overheated, electric fans bare come on and if they do the cool the engine down in 30 seconds at idle. In the heat of the Texas summer the AC condensor fans keep the engine on temp and the main fans rarely kick in. Completely transformed the cooling and I never looked back. The amount of hot air this radiator pumps out is unbelievable.

From research I found that Radiators are basically service items that loose efficiency (heat exchange ability) and need to be replaced occasionally. Copper is more durable, aluminium is more effective and (nowadays) cheaper. Technology has moved on. Plastic side tanks/fittings can crack but last a good 10 years. There are fairly cheap radiators out there that work extremely well, but might have a limited life depending on use (heat cycles) but they last plently long enough. It is easier to budget for a replacement radiator sometime in future say every 10 years or so.
 

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Discussion Starter #40
SOLVED!!!

JS5D, I know exactly where your comping from the radiator being suspect. I had a similar issue on my Ford Excursion 7.3 and ultimately yes it was the radiator. In this case, the radiator at least for me was not really suspect as the previous 4.6 motor was not overheating at all. So when I swapped the motor over to the 4.2 it just didnt seem like the issue was the radiator. So to rule it out I took it to a company here with a spare one and they confirmed the spare was bad but the one I was using was good so it in essense ruled it out. They tested it for pressure leaks and flow so it was good enough for me to rule it out.

SOLUTION: AIR BUBBLE/ BLEED BLEED BLEED

Well all, before I decided to dig into the upper intake I decided to once again try like hell to bleed all the air out. Im new to rovers and after some of your comments and reading some other comments it really sounds like these Rover V8's really really dont like any air. So, I figure what the hell, I ended up picking up a 40.00 coolant funnel put the truck on a incline, lifted up the expansion tank so no kinks and way up above any part of the system and saw quite a bit of air bubble out. I let her cool down, repeat, then left the funnel full and let it sit overnight. What do you know...... no more overheating.... Ive NEVER seen a system so difficult to all the air out but that did it.

Thanks ALL for your help!!! My Daughter has high functioning Autism and she just loves her Dinosaurs. She was devastated. Very hard sometimes for her to understand things and change can be difficult for her. When I tore down the 4.6 after discovering a blown head gasket I discovered that it was leaking between the liner and the block and honestly, I just completely HATE the Bosch 4.6 setup. Dam near everything has to come apart to change anything it seems and then when you add the secondary air.... I was just so over it. I am kind of lucky as I can register it in Florida to avoid emissions. I was looking at all kinds of options but I basically fell into this 4.2 and the more I studied the more I liked it. I would read on Discoweb and everyone would say that swap is not possible because the electronics are so integrated. Well, I did it. I probably should have documented the entire engine/transmission swap. It really was NOT that difficult and was for the most part a bolt in swap. Old school is sometimes the best school. Now, with the 4.2 I have a stout bottom end, ported and polished heads, hotter cam, and high performance distributor and the 4HPZF22 from 93 is all mechanical and the only change was hoses needed adapters and just had to wire in the reverse lights and start inhibitor, 4 wires and that was it so major plus. If the 4.2 motor ever needs a complete rebuild that block IMO is a better investment than ANY 4.0 or 4.6 block. If this one blows up Id be more inclined to drop the coin to top hat sleeve it. I realize it was a lot of luck the only reason I wound up with the 4.2 was because my friend was doing an LS1 swap on his Defender.

Yes, there is small list of things that will need to be worked out but nothing major or things that can live without. ABS, Hill descent as an example, turning off the everyblinking Green lights for the transmission, tach gauge etc. Hoever just to see her smile ear to eary today was worth all the hard work and aggravation. Now, maybe I can start to work on my projects.. :)

I do think I am going to source the original fan shroud and go back to the original fan setup. The alternator can't keep up with the rack lights AND the electric fans. I'll have to see what the cost is for a 100 or 125 amp alternator. I'd like to have the Viscous fan and may be dual pusher for those 100 degree days in summer. Besides, seriously in the middle of nowhere when driving down to Southern Utah and not having a reduntant setup Id like the electric as a back up.

Posted some pictures of the build for my daughter. Thanks again for all of your help!!


Rodge
 

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