Temperature spikes in 4BD1T

[rijidij]

Ever since I fitted the 4BD1T to the County I have noticed the occasional spike in the water temp. What I mean is, most of the time the gauge sits on 80 - 82 where it should be, but occasionally it will suddenly (in a matter of about 30 secs) shoot up to approx 100. It happens under normal driving conditions. If I keep driving, the temp will slowly go back to normal ( in a matter of a minute or two)
My first thought was air trapped in the system as it had been completely drained for the conversion. I thought I fixed it by installing a fitting on the thermo housing to top the water up from the highest point. (truck thermo housing doesn't have filler cap like the Landy one) This seemed to work as I didn't have a problem for a whole 8000 km outback trip.
But anyway, it's started doing it again.
There are no leaks in the system and it holds pressure for days and is clean.
The thermo and O ring was brand new when I fitted the engine (about 25k ago), but it is not a genuine Isuzu thermo.......this is now the thing I suspect could be causing the problem, maybe sticking or something. Should I have listened to my mate who told me to " Make sure you fit a genuine thermo".
I know the gauge is ok as I fitted an 'Engine watchdog' and this confirms the temp increase. Any thoughts ??

https://www.aulro.com/afvb/images/imported/2008/11/291.jpg
https://www.aulro.com/afvb/images/imported/2008/11/292.jpg

[Dougal]

Last time I was looking, I couldn't even find a non-genuine thermostat.

I'd go there first.

[incisor]

sounds like a thermostat to me, just because they are new dont mean they work okay..

[C H T]

Rijidij

I would look at getting a genuine thermostat form Isuzu - I paid something like $65.00 for thermostat and "O" ring. My 4BD1T tends to spike a bit in water temp on big hills and then gradually recovers - it could be that the thermostat is not fully open when the load comes on the engine which causes the spike in water temp - see my post on water temps - I have been thinking of fitting a larger radiator.

Christopher

[justinc]

Murray,

I would definately go with the new genuine thermostat. Mine was sticking open, as I went down hills the temp would drop right off. When I replaced it, it still had the 1988 date stamp on it:o
That means it had travelled 500,000+km.

Anyhow,the new one is fine now, with my 3 row RRC radiator, it sits exactly half, even with towing and the A/C on etc.

JC

[rijidij]

Thanks guys,
Like I said I should have listened to my mate who told me to " Make sure you fit a genuine thermo".
A member on here has generously offered me a spare brand new thermo. It will be interesting to see if it makes the difference.
It's so easy to fit a new thermo, it would be the first thing I try, but I thought I would pose the question just in case there had been any other issues with spiking.
I had the V8 in the County for 13 years and whenever I had any hint of temp problems it was always the thermo.

Cheers, Murray

[rijidij]

Took the County for a run today with a new genuine thermo fitted. It was only about a 50km trip, but all seems well so far. Probably need a longer, warmer drive to really test it out. The temp seemed more stable with the new thermo though.
Visibly, the genuine thermo looks to be better quality than the non-gen one.
Hopefully it's the end of the problem.

[rijidij]

I've had the Genuine thermo in for quite some time now and it has been much better, but it still spikes now and then. Most noticably, when I'm travelling at 100 kph it's all good, then I slow down to go through a small town and the temp will suddenly spike up to 100*. It only stays there for 10 or 20 seconds, then slowly goes back to 82* where it's supposed to be. It's also no problem while 4WDing in the bush at high or low RPM, even when working it hard up long steep hills. It never actually 'overheats'.
I noticed it's losing water out the overflow hose from the pressure cap. On the trip we just did, 2 mornings in a row I put approximately 1.5 litres in to top it up.
The rad cap is stamped with the numbers 16 and 110.......is this the correct cap ? It was a new one I got when I had the V8 in and still appears to be in good condition. Is the Isuzu supposed to have a different cap ?

Cheers, Murray

[Offender90]

Based on the symptoms, I'd say its likely to be a faulty pressure cap (i.e. it's not holding pressure)

If you're losing coolant through the cap, either its not holding to its rated pressure, or you have air in the system.

If its a V8 cap, it's rated to 16 psi. At this pressure, the boiling point of water is 121 degrees. If it didn't exceed 121 degrees, the pressurised coolant shouldn't boil (and there shouldn't be any loss).

Alternatively, if the pressure cap doesn't hold ANY pressure, the coolant would start boiling at exactly 100 degrees, so the temperature would reach 100*C and then stay there while the coolant is boiling (explaining your coolant loss). If its holding some pressure it would go past 100*C, and how much past would depend on how much pressure the cap is holding.

If your pressure cap tests OK, I would look for a split in the coolant reservoir, or a leak elsewhere in the system - (it would have to be one of the higher points in the system).

I wouldn't worry about the temperature spiking for a short time after slowing down from 100km/h, especially if the system isn't holing pressure. => At high load the engine is producing plenty of heat, but at that speed, the airflow over the radiator gives it enough capacity to dissipate it. As the car slows down, the radiator has instantly lost some of its ability to transfer heat, while there's is heat temporarily stored in the engine block even after the engine stops producing it. The coolant temperature increases to a new equilibirum point until the heat stored in the block is dissipated, after which it goes back to normal temp as determined by the thermostat.

It fits, I just hope its that simple.

Cheers

Bojan

[rijidij]

Thanks Bojan,
The system actually holds pressure even after sitting for days, so I don't think there is a leak anywhere. I will test the cap as you suggest. The fluid loss is deffinately out the overflow at the cap. Anyway, a cap is such a low cost item, it might be worth getting a new one.
I've got the radiator from the truck my engine came from. I'll have a look at the rating on that cap just for interest.
Can anyone tell me the rating for the pressure cap on a factory Isuzu 110 ?

Cheers, Murray

[Offender90]

Thanks Bojan,
The system actually holds pressure even after sitting for days, so I don't think there is a leak anywhere. I will test the cap as you suggest. The fluid loss is deffinately out the overflow at the cap. Anyway, a cap is such a low cost item, it might be worth getting a new one.
I've got the radiator from the truck my engine came from. I'll have a look at the rating on that cap just for interest.
Can anyone tell me the rating for the pressure cap on a factory Isuzu 110 ?

Cheers, Murray

The one that I have on mine is 15psi - it looks as aged as the rest of the car, so it could be original. It's made by Unipart, and has a part number "BRO 9132" stamped on it.

On a side note, when you say "The system actually holds pressure even after sitting for days" do you mean it stays pressurised for that long?

[rijidij]

On a side note, when you say "The system actually holds pressure even after sitting for days" do you mean it stays pressurised for that long?

Yeah, after the County has been sitting for a couple of days, I've undone the cap and it was still pressurised. Not as much as at running temp of corse, but enough to gurgle coolant up to the header tank.

Murray

[Dougal]

Does your county run a full flow heater?
My rangie does, but my truck engine was originally intended to run a bypass heater. So I have the bypass hose from water pump to thermostat blocked off.

Seems to work for me.

[The Mutt]

Does your county run a full flow heater?
My rangie does, but my truck engine was originally intended to run a bypass heater. So I have the bypass hose from water pump to thermostat blocked off.

Seems to work for me.

What is the difference between a Full Flow Heater and a Bypass Heater. I hooked up the standard Rangie system to the water pump of the 4BD1.

Glenn

[Bush65]

As I understand, the full flow heater in rangies has the full flow of water though the heater core at all times - one reason why it is hot inside during summer. The air, not water is regulated by the hot/cold heater control.

This allows the pump to circulate some water through the engine (but not radiator) before the thermostat opens.

[rijidij]

Does your county run a full flow heater?
My rangie does, but my truck engine was originally intended to run a bypass heater. So I have the bypass hose from water pump to thermostat blocked off.

Seems to work for me.

The heater hoses are hooked up the same as they were in the truck, I think it's a full flow system.

[rijidij]

I've got the radiator from the truck my engine came from. I'll have a look at the rating on that cap just for interest.
Can anyone tell me the rating for the pressure cap on a factory Isuzu 110 ?

Cheers, Murray

The only number stamped on the pressure cap that was on the truck rad is 90, does anyone know what it indicates ?

[justinc]

The only number stamped on the pressure cap that was on the truck rad is 90, does anyone know what it indicates ?

Murray, 90 Kpa, or 13psi in the old speak:p

JC

[Dougal]

The heater hoses are hooked up the same as they were in the truck, I think it's a full flow system.

In that case you've got two bypasses which could be either sharing water flow or having water circulate from one through the other.
The Isuzu truck cab heater is a bypass, it shuts off water flow when not needed.

Take off that short hockeystick hose, block it and see if your problem disappears.
BTW, that little hose matches a mini part exactly.

[yt110]

I converted mine to a recovery system so the header tank is always full,just fitted a recovery cap to the header tank and a overflow bottle alongside,it has stopped air pockets forming in the cooling system as the top of the heater core is higher than the bleading plug on the thermo housing.I don't have any temp spikes

[rijidij]

I converted mine to a recovery system so the header tank is always full,just fitted a recovery cap to the header tank and a overflow bottle alongside,it has stopped air pockets forming in the cooling system as the top of the heater core is higher than the bleading plug on the thermo housing.I don't have any temp spikes

What's the difference with a recovery cap ? Could you explain a little more how your system works.

Cheers, Murray

[yt110]

Ok.a recovery type radiator cap has 2 seals,so when the cooling system heats up coolant is pushed out through the cap into the recovery bottle,as the system cools coolant is drawn back into the header tank.Its the same as lots of jap cars etc use.When you check the standard system the header tank will always be down a bit,because of expanding coolant,this way when you check the header tank it will be full and no air pockets which can upset sender units and thermostats,also pockets of air can cause corrosion in the cooling system.Most parts suppiers should be able to supply a recovery type cap to replace the standard cap and a plastic overflow bottle.Hope this helps. Jim.

[Adrian18]

Did you get a solution for your problem with temp and loosing coolant ...mine does exaxtly the same as you have described .

[Adrian18]

This is my bypass set up dougal is this ok sort of looks like the heater is a bypass too the heater never gets very warm....just drove to work 27k after filling coolant levels last nite I jury rigged a bottle under the over flow from the expansion tank checked it just now full 2.5 lt would have expected 1lt but 2.5 ..the temp gauge was all over the place to 50 to 90 thermostats stuff it only a couple of months old too

[87County]

I read through this thread with interest and unless I have missed it, no one has yet mentioned having the radiator cleaned ("rodded").

Over the years and with various vehicles this has proved to be a very positive thing to do for me, it addesses unknown potential problems as well.

If you have a tame radiator repairer nearby and you take it into them they'll take the top and bottom off clean it, and refit the tanks and retest for (I guess) less than $100. They'll also do minor stuff like straightening bent fins and painting it on completion.

While it is out of the vehicle you can give the whole system a thorough flush.

For the water component of the new coolant mix I have only been using rainwater, because depending on where you are tap water can have lots of lime in it.

Apologies if this reads like "teaching to suck eggs" but it didn't seem to have already been covered here yet.

[rijidij]

Did you get a solution for your problem with temp and loosing coolant ...mine does exaxtly the same as you have described .

I never found the cause of the problem, but as long as I have the radiator cap undone to the stopper the temperature is stable. It does use water, but not enough to worry too much about.

Cheers, Murray

[jorjatom68]

On my isuzu I never had temp problem but itwas using a smal amount of water. When I looked into it the pipe inside the header tank that pulls the water back to the motor when it cools was broken off. A small piece of copper pipe soldered in fixed it. If you ever need a new radiator at any stage as the are near impossible to find in god nick and if you do they have a crap chinese core, ask PWR. I got one for mine so they have the template now. Not everyone likes alloy radiators but they made mine for a not much more than a recore and they got it powder coated for me. Very helpful people.

[Adrian18]

Well since I'm leaving on a trip tuesday 4 days away I took the radiator out and took it to get cleaned it turn out the tanks on both sides were half full of cememted crud...mmm so it got recored $775 :eek:
I had 50km of fine driving then 1 spike but it been fine since so buggared if I know

[Adrian18]

Well looks like the new radiator did the trick we're just driven up from hobart and waiting from the boat at devonport .she drove great and temp was stable

[Dougal]

Well since I'm leaving on a trip tuesday 4 days away I took the radiator out and took it to get cleaned it turn out the tanks on both sides were half full of cememted crud...mmm so it got recored $775 :eek:
I had 50km of fine driving then 1 spike but it been fine since so buggared if I know

The last spike could have been an air bubble finding it's way out.