Cooling System Sanity Check

[cummo]

I am in the process of changing out the coolant in my GS 4x4, which as it happens is the first vehicle I've had with a cross flow radiator.
First step was to give the system a flush using a proprietary radiator flush & clean then back in the shed to cool down a little before dumping the coolant.
Then:-
- Coolant dumped using bottom hose and block drain with the brass filler plug out. Coolant was very clean; no evidence of rust or scale
- Top radiator hose inverted and distilled water poured down through the radiator till water ran clear
- Bottom hose inverted and distilled water poured through water pump and block till water ran clear
- Surge tank removed and flushed out
- Drain closed, hoses back on
System filled with distilled water to be run up to temperature and then drained and then whole sequence will be repeated with the plan being that any residual fluid in there will be either just distilled water or extremely dilute original coolant. The radiator will come out after the third flush to be taken to my local independent radiator guy for a check over for good measure.

The motor has always ran just under the 80 degree mark no matter what it's doing or how the ambient air temperature is. I filled the system after flushing using a proprietary coolant funnel set-up so that the air could bleed out during filling, and filling would be done with a positive head of water. All OK; top hose eventually gets hot as the thermostat opens and the motor idles away till usual operating temperature is reached. What surprises me though is that the bottom hose eventually only gets and stays barely warm. The top hose and thermostat housing get respectably hot, but the bottom hose gets nowhere near as warm.

I'm hoping there's nothing wrong in this, just that the cooling system is in good order and is working well, delivering cooler water water back to the block. The radiator core is not the original one - it appears to be a re-core - but is externally in good condition with no damaged fins etc. I will be installing a new genuine Isuzu thermostat as part of the final coolant fill so that I know it's benchmarked right, and I will then have a spare on hand for trips.

If anyone thinks there is anything untoward with the way the cooling system as described above is working advice would be appreciated.

Cheers, Dave

[Blknight.aus]

nope, for an idling engine that sounds about dead on the money.

[Chris078]

Only thing that sounds slightly out to me is the 'runs just under 80c' comment.
Should be about 10c hotter than that. It's an 82c thermostat.
Obviously it's not overheating - you'd have fried it by now if it was.
Leaves the temp sensor or the gauge as being incorrect.

[Mick_Marsh]

It's an 82c thermostat.
Is that starts to open at 82?C or is fully opened at 82?C?

[Chris078]

as far as I know. Starts to open at 82c

part # is 5137700301

It's a wax thermostat, which according to Wikipedia (https://en.wikipedia.org/wiki/Wax_thermostatic_element)will start opening at it's nominated temperature. In this case 82c.
Mine sits at about 88c (if my gauge and sender are accurate. Who knows) when it's fully warmed up - which takes about 15-20 minutes.

[Chris078]

Just a thought.
My local NatRad (http://www.natrad.com.au/?products/engine-coolants) quoted me $150 to drain, flush, refill, pressure test etc.

Considering how much of a pest it is to drain/flush/fill the cooling system on the Perentie is, that is not bad value. Plus if they stuff up and get an air-lock when they re-fill it, that's on them and not you.

Might be worth considering.

[BadCo.]

Agree with Chris about temperature, but I reckon the thermostat is opening too soon. I had the same problem, it would sit a touch under 80 with a radiator muff and under load.

A new thermostat was an easy fix and it now sits in the green (or is it blue?) all the time.

[Chris078]

Agree with Chris about temperature, but I reckon the thermostat is opening too soon. I had the same problem, it would sit a touch under 80 with a radiator muff and under load.

A new thermostat was an easy fix and it now sits in the green (or is it blue?) all the time.


If the thermostat is opening too soon, it should still get up to temperature eventually shouldn't it? - sitting around 88c or so.

I would have thought that would indicate a fault with the temp sender or gauge, rather than the thermostat. Interesting that changing the thermostat fixed your problem.
Maybe you had some gunk on the sender and when you changed the thermostat, you cleared it out?

[BadCo.]

If the thermostat is opening too soon, it should still get up to temperature eventually shouldn't it? - sitting around 88c or so.


Not if it is fully open well under 80c?

[Chris078]

I suppose if you're just idling it wouldn't get there. If you're driving it, It should get to full temp, just take an extra few minutes.

That is just my personal opinion. I could very well be wrong.

[cummo]

New OEM Isuzu thermostat picked up today. Isuzu P/N 8944723311 (82 deg C).
Am also going to take Chris's suggestion and fit a new temperature sender. The existing sender is a VDO unit; hopefully a local gauge shop or Repco will stock or be able to source one.
Once the radiator is flushed and tested, hopefully all elements will be ticked off bar the gauge.

[Chris078]

Maybe change the thermostat and see if that fixes the problem like it did for BadCo.
Before chasing down a sender.



The temperature sender part number is AYG 9603 (Which seems like a Landrover number, not an Isuzu one)

which is odd as I can't find that number on any supplier sites (lrdirect.com etc)
Maybe you have to get it from Land Rover themselves.

Found this ancient thread from Bearman
http://www.aulro.com/afvb/isuzu-landy-enthusiasts-section/69059-part-number-temperature-sensor.html

That number, PRC2506, does come up, but I really don't know that it's the right one for a Perentie.

[Bearman]

Maybe change the thermostat and see if that fixes the problem like it did for BadCo.
Before chasing down a sender.



The temperature sender part number is AYG 9603 (Which seems like a Landrover number, not an Isuzu one)

which is odd as I can't find that number on any supplier sites (lrdirect.com etc)
Maybe you have to get it from Land Rover themselves.

Found this ancient thread from Bearman
http://www.aulro.com/afvb/isuzu-landy-enthusiasts-section/69059-part-number-temperature-sensor.html

That number, PRC2506, does come up, but I really don't know that it's the right one for a Perentie.

It's not Chris, that's for a V8 petrol 3.5L. The AYG 9603 is the correct one for a perentie - it's actually a VDO sender as the perenties have VDO gauges but of course allocated an AYG number by LR so they can triple the price :eek:

[Chris078]

Thanks Bearman. I had no idea where he got that number from, that's why I mentioned that it may not be correct.

If AYG9603 is a VDO part, one assumes that a VDO stockist will be able to supply it at 1/4 the LR cost?!


Well now, out of interest (and I have a day off today) I rang Land Rover here in Brisbane.
The genuine part AYG9603 is $38.75 inc GST! I'm getting one to throw in the spares box.
The part is in Melbourne, should be here tomorrow for me.

[BadCo.]

I suppose if you're just idling it wouldn't get there. If you're driving it, It should get to full temp, just take an extra few minutes.

That is just my personal opinion. I could very well be wrong.

I disagree. But i could also be wrong! :D

If the thermostat is always open then there is nothing controlling the temperature. Its always going to be the coldest it can be.

We need someone who actually knows what they are talking about haha

[Chris078]

I disagree. But i could also be wrong! :D

If the thermostat is always open then there is nothing controlling the temperature. Its always going to be the coldest it can be.

We need someone who actually knows what they are talking about haha


lol. I was thinking that because the temperature that it sits it when fully heated (88c or so) is above the opening temp for the thermostat (82), that it would still get to that 'heated' temp, it would just take longer to get there.

[Mick_Marsh]

I disagree. But i could also be wrong! :D

If the thermostat is always open then there is nothing controlling the temperature. Its always going to be the coldest it can be.

We need someone who actually knows what they are talking about haha
There is a hysteresis in the opening of a thermostat. It never fully opens for normal operation. It should only fully open when the ambient is really hot. The thermostat is there to regulate the flow rate in the cooling system, keeping the coolant warm in cold ambient and cool in hot ambient. If the thermostat opens early, the motor will always be cooler than it should be.
Let's face it, if there wasn't a problem with the motor being as cool as it can be, why have a thermostat?
I had a Gemini years ago. The thermostat failed closed. To get around whilst I waited for the parts to arrive, I removed the thermostat. The temperature needle never moved from the bottom stop and the automatic choke was on all the time. The car was running quite rich.

[BadCo.]

Thanks Bearman. I had no idea where he got that number from, that's why I mentioned that it may not be correct.

If AYG9603 is a VDO part, one assumes that a VDO stockist will be able to supply it at 1/4 the LR cost?!


Well now, out of interest (and I have a day off today) I rang Land Rover here in Brisbane.
The genuine part AYG9603 is $38.75 inc GST! I'm getting one to throw in the spares box.
The part is in Melbourne, should be here tomorrow for me.

Let us know if it has a VDO part number!

[Chris078]

Let us know if it has a VDO part number!


I can! This is the VDO number that the Land Rover guy gave me

It's 6685-66-095-8448 - for the temp sender

[cummo]

Picked up a new VDO temperature sender from the local instrumentation shop today.
VDO P/N 320.002; 40-120 degree range, 1/8-27NPT thread, 1/2" AF hex, pin connection. $15 all up. Didn't have my original with me, but based on the stamping so on the hex flats the parts guy is 99.9% certain it's the goods.
For the small dollars involved worth replacing just to benchmark it.

[Chris078]

Picked up a new VDO temperature sender from the local instrumentation shop today.
VDO P/N 320.002; 40-120 degree range, 1/8-27NPT thread, 1/2" AF hex, pin connection. $15 all up. Didn't have my original with me, but based on the stamping so on the hex flats the parts guy is 99.9% certain it's the goods.
For the small dollars involved worth replacing just to benchmark it.


give them a call and see if that part number matches up with the post above which is the VDO part number that the Land Rover have as the cross reference for that part.

[Blknight.aus]

uhhh guys..

its a perentie.. for the major service

is the top radiator hose hot, is the return from the radiator cold?

heres how you field test the cooling system.

blanket the radiator.

warm the engine up,

top hose hot, bottom hose a little cooler, temp gauge normal? heater working?

good. go drive it leave the blanket in place turn the heater fan off leave it set for hot air.

temperature gauge rising after about 5 minutes of driving? good.

turn the heater fan on flat out pull over remove the blanket, drive off. temp gauge coming down?

cooling system checked.

for the alt major service, replace the thermostat and pull and flush the radiator/rod it after you do a chemical flush of the system. Replace hoses as requried.

done.

[BadCo.]

I can! This is the VDO number that the Land Rover guy gave me

It's 6685-66-095-8448 - for the temp sender

This doesn't seem to be a VDO number?


Picked up a new VDO temperature sender from the local instrumentation shop today.
VDO P/N 320.002; 40-120 degree range, 1/8-27NPT thread, 1/2" AF hex, pin connection. $15 all up. Didn't have my original with me, but based on the stamping so on the hex flats the parts guy is 99.9% certain it's the goods.
For the small dollars involved worth replacing just to benchmark it.

This is good info, if it turns out to be correct.

[cummo]

I'll be installing the VDO 320.002 sender on Saturday so fingers x'd it'll fit OK. The temp range is right, hex size right and has the correct pin connector. The probe length is the only unknown. If the probe length the is the same and the NPT thread correct then all should be good. I'll post up how it turns out.

Cheers, Dave

[Chris078]

You should be fine Cummo.
I picked up mine from Land Rover today
It's got a LR sticker on it with AYG9603 and 668566-095-8448 on it.

It's in a VDO branded package with 320.002 on the packaging. Reckon you're on the money.

Imgur: The most awesome images on the Internet (http://imgur.com/a/x3i6P)

excuse the terrible photos, my camera has pretty much died and that's the best picture it will take.

[cummo]

Went for the first run since putting the cooling system back together. New Isuzu 82-degree thermostat installed with jiggle/air bleed valve installed towards housing outlet, new VDO sender, radiator removed, flushed & pressure tested with top marks from the radiator guy. Block flushed up and down with air/water pressure gun, (clean as a whistle), 2 fills and dumps with distilled water, final fill with Nulon L/L coolant.

Warms up and stays relatively stable at what I interpret to be about 95 degrees. Hot water flow from the block via the thermostat seems to happen at about 90 a 92 on the gauge. Markedly different from the old arrangement where the gauge showed a pretty constant 80-degrees.

Logic tells me there should be no issues what with everything flushed and/or new. I'm thinking maybe the gauge earth; I do get a flicker on all gauges with the blinkers operating, but I thought that was normal anyway.
Maybe this is the new order of things and it is OK to run at this temperature. As usual all thoughts/suggestions appreciated.
Cheers, Dave

[Chris078]

Few degrees higher than mine (normally around 87-88c or so) probably variances in the gauges rather than anything else.
at least it's more accurate than what it was.

Check the earth lead from the alternator and starter. The earth for most of the electrical system is ..... rudimentary at best in this car. It's a 4 gauge line from the starter back to the harness behind the fuse box and all the earths are simply soldered to that 4 gauge line.
<edit> the power to the system is much the same!

if you pull the cluster, it would be pretty easy to run a line from the battery to the cluster (you will be able to see that the earth wire there is shared between the gauges via a single post, just attach your additional line to that) to test.

I've been meaning to do the same thing for ages, maybe next weekend.
Seeing as I can't drive until I get this drivers seat fixed.

[BadCo.]

Warms up and stays relatively stable at what I interpret to be about 95 degrees. Hot water flow from the block via the thermostat seems to happen at about 90 a 92 on the gauge. Markedly different from the old arrangement where the gauge showed a pretty constant 80-degrees.


Seems warm, mine sits exactly on 82 under normal circumstances.

[cummo]

Hi Chris. As my lack of electrics is legendary, I assume you mean run a temporary lead from the negative battery terminal direct to the common gauge earth in order to bypass the existing body earth? This in my mind (which is a dim place) may then show whether existing gauge earth is the problem. Hopefully I've interpreted you correctly. Dave

[cummo]

Before I delved into the spaghetti of wiring to find and check the temp gauge earth, I pulled the new thermostat out and did I a side-by-side comparison with the old one in a saucepan brought them up to boiling. Should have done it for the hell of it before I installed it. I did it a few times to make sure; old thermostat cracked open to let air bubbles through at 76-78 and opened visibly at 82 degrees; the new one cracked open at 88-89.

Not sure if the later opening thermostat is causing the continual higher operating temperature on the gauge; other than the new correct sender and coolant nothing else has changed. Additionally my understanding of thermostats is that they should work correct from day one; AFAIK there isn't a "bedding-in" period or the like following which they "loosen up".

Heading back to the Isuzu dealer tomorrow to discuss and possibly order in a replacement. Heading from Newcastle to KLR at Windsor on Thursday; may end up putting the old thermostat in for the trip.

Cheers, Dave

[Chris078]

Before I delved into the spaghetti of wiring to find and check the temp gauge earth, I pulled the new thermostat out and did I a side-by-side comparison with the old one in a saucepan brought them up to boiling. Should have done it for the hell of it before I installed it. I did it a few times to make sure; old thermostat cracked open to let air bubbles through at 76-78 and opened visibly at 82 degrees; the new one cracked open at 88-89.

Not sure if the later opening thermostat is causing the continual higher operating temperature on the gauge; other than the new correct sender and coolant nothing else has changed. Additionally my understanding of thermostats is that they should work correct from day one; AFAIK there isn't a "bedding-in" period or the like following which they "loosen up".

Heading back to the Isuzu dealer tomorrow to discuss and possibly order in a replacement. Heading from Newcastle to KLR at Windsor on Thursday; may end up putting the old thermostat in for the trip.

Cheers, Dave

Then they are both not working properly.
as per my post (http://www.aulro.com/afvb/coil-sprung-military-land-rovers/234139-cooling-system-sanity-check.html#post2514616) a while back the thermostat should start opening at its nominated temperature (82c in this case) and according to my mechanic should be fully open no more than 3-5 degrees above that.

Personally (because I am supremely paranoid about overheating things) for a long trip I'd put the old one it, and have it run cool and burn a bit more fuel than the new one which is going to make your engine run hot.

[Gardi01]

Agree with Chris about temperature, but I reckon the thermostat is opening too soon. I had the same problem, it would sit a touch under 80 with a radiator muff and under load.

A new thermostat was an easy fix and it now sits in the green (or is it blue?) all the time.
Thanks, mine is definitely running too cold. Not good.

[BadCo.]

Thanks, mine is definitely running too cold. Not good.

The other thing you could check is the earthing. But I'm fairly sure if there was a bad earth it would read high.