OKA 268 OVERHEATING

More
06 Mar 2018 12:06 #1 by mort
mort created the topic: OKA 268 OVERHEATING
Hi All,
Myself and Vince was driving back home after the gathering yesterday when on the UHF he said he was overheating so pulled over to check.
Coolant was full but it didnt look like there was any flow through the radiator so pulled out the thermostat incase it had stuck closed.
Less than 3Klm's down the road red light on, luckily we were in Narrogin so pulled into Beaurepairs ( which were shut ) and pulled out the radiator as there wasn't any flow so we hoped it may have been blocked.
It did have a lot of muck and scale in it but in the end water flowed freely.
we set off again 3 KLm's down the road red light on again and gauge up to 120 so pulled over and I took the radiator cap off and water cool but engine hot, the only other thing it could be is water pump unless anyone else has some ideas that I havn't considered.
The OKA was towed to a farm that Vince knows the owner and left it there.
Martyn
Attachments:

Please Log in or Create an account to join the conversation.

More
06 Mar 2018 15:42 - 06 Mar 2018 15:52 #2 by dandjcr
dandjcr replied the topic: OKA 268 OVERHEATING
Martyn, that's not a good look, but other than a blocked waterway/hose, the water pump does seem a suspect.

Were there any noises associated with the overheating (pump wear)? Being gear driven, it will still attempt to rotate and you don't want the gears to be damaged.

If there are no other internal leaks (eg into cylinders via a blown head gasket and white smoke) inserting an electric water pump into the bottom hose would solve the problem temporarily. (Davies Craig pumps are available from Supercheap ), Water should flow past the pump impeller to some degree even if it's jammed or spinning on its shaft.

If you had a spare water pump gasket (or could make one) you could remove its cover and check its internals before driving long distances (assuming the LT is similar in this area to the XT).

David


David and Janet Ribbans - Oka 148
Oka148 profile here.
Visit our technical and travel blogs: here.
Attachments:
Last Edit: 06 Mar 2018 15:52 by dandjcr.

Please Log in or Create an account to join the conversation.

More
06 Mar 2018 18:38 #3 by Holmz
Holmz replied the topic: OKA 268 OVERHEATING
David, that is a good idea about the Davies-Craig, as that would be pretty easy to jerrry-rig in the middle of woop-woop.

Please Log in or Create an account to join the conversation.

More
07 Mar 2018 07:39 #4 by mort
mort replied the topic: OKA 268 OVERHEATING
Hi David,
No there was no noise to indicate that it is/was the pump and we flushed the engine with no sign of restriction so until we can get a new pump installed then pull the old one apart we wont know but I can only guess that the impeller is loose on the shaft.
Martyn

Please Log in or Create an account to join the conversation.

More
07 Mar 2018 08:40 #5 by Holmz
Holmz replied the topic: OKA 268 OVERHEATING

mort wrote: Hi David,
No there was no noise to indicate that it is/was the pump and we flushed the engine with no sign of restriction so until we can get a new pump installed then pull the old one apart we wont know but I can only guess that the impeller is loose on the shaft.
Martyn


It is either not moving water through enough radiator cores, as in a plugged radiator, or the pump is not moving water at all.
I have sworn it was one when it was the other.

Maybe some 20 litre buckets could have a pickup hose into one bucket to see of the pump moves the fluid into the other?

Please Log in or Create an account to join the conversation.

More
07 Mar 2018 18:22 #6 by mort
mort replied the topic: OKA 268 OVERHEATING
Hi All,
Can anyone tell me the correct pressure for the radiator cap as 268 has 18psi which I would think is high but maybe not.
Martyn

Please Log in or Create an account to join the conversation.

More
07 Mar 2018 20:01 #7 by Holmz
Holmz replied the topic: OKA 268 OVERHEATING

mort wrote: Hi All,
Can anyone tell me the correct pressure for the radiator cap as 268 has 18psi which I would think is high but maybe not.
Martyn


I am sure you know this, but I will wax on, in the karate Kid sense...
Water is better than coolant in terms solely of heat capacity.
So it is better to run pure water and then control the boiling point with pressure than with a coolant that has a higher boiling point.
^This^ ignores corrosion inhibitors, and anti bubble surfactants additives, which are good... and well as freezing temps.

And the heat transfer is a function of the thermal gradient, so the hotter the radiator And the cooler the air, then the better the heat transfer.

Basically I would probably leave that 18 psi cap, unless the radiator is only good for 12 psi... then it may be better to have a boil over than a burst radiator???
In real life I am not sure if the overflow is based upon the 18 psi or not, but in a system working at 80 or 90 C operation, the pressure should not approach the cap pressure.

But ^these^ maybe more like ideas to help me understand what is proper in terms on an OKA.
However I do believe I have the theory relatively sound. And I am interested in how it all goes.
Luckily my old OKA seems to hold 80C ;)

Please Log in or Create an account to join the conversation.

More
08 Mar 2018 04:44 #8 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: OKA 268 OVERHEATING
I thought 15psi was the standard radiator cap fitted, 374 has always had a 15psi cap as have others I've looked at.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.

Please Log in or Create an account to join the conversation.

More
08 Mar 2018 04:53 - 08 Mar 2018 04:58 #9 by dandjcr
dandjcr replied the topic: OKA 268 OVERHEATING

Peter and Sandra OKA 374 wrote: I thought 15psi was the standard radiator cap fitted, 374 has always had a 15psi cap as have others I've looked at.


Can't quite read the pressure on my cap unless the 7/50 means something, but it may not be original anyway.



A quick look at the Tridon catalog shows caps with ratings from 7 to 23 psi, so 18 would seem to be at the high end of the range.

David and Janet Ribbans - Oka 148
Oka148 profile here.
Visit our technical and travel blogs: here.
Attachments:
Last Edit: 08 Mar 2018 04:58 by dandjcr.

Please Log in or Create an account to join the conversation.

More
08 Mar 2018 06:23 - 08 Mar 2018 06:29 #10 by mort
mort replied the topic: OKA 268 OVERHEATING
Hi Peter and David,
I have just cleaned and checked mine and it is 13 psi so maybe there is no std or they get replaced with whatever is around at the time.
7 psi is about 48 Kpa so that is what is on your cap 7 over 50
If more people can put up their cap pressure it may show a consistant pressure over a number of vehicles.
Martyn
Last Edit: 08 Mar 2018 06:29 by mort.

Please Log in or Create an account to join the conversation.

More
08 Mar 2018 06:36 #11 by outyonda
outyonda replied the topic: OKA 268 OVERHEATING
XT has A header tank
LT has A expansion tank

diferent pressures, different caps.

OKAs 091, 093, 094, 113, 346x6 & 405

Please Log in or Create an account to join the conversation.

More
08 Mar 2018 09:47 - 08 Mar 2018 09:50 #12 by Dean and Kaye Howells
Dean and Kaye Howells replied the topic: OKA 268 OVERHEATING
7 psi is the correct cap for the LT and I would assume the same for the XT though having a higher pressure cap won't be causing the overheating but it will be putting undue strain on the cooling system by having it run at a higher pressure than it was designed to be. The Oka has a bypass type thermostat which if stuck closed will result in little or no coolant flow through the radiator and lead to overheating. Similarly a failed viscous fan coupling will also cause overheating. Was the radiator hot ?

Removing the thermostat and running without one can be a risky business as if this is not the problem there is nothing to regulate water flow through the engine/radiator and removal may actually make matters worse. note. the thermostat is a consumable item and has a useful/reliable life of around 7 years.

To check the viscous coupling, with the engine off, cold start the engine with the engine cover open, the fan should roar and blow vast amounts of air for a few seconds prior to the viscous coupling disengaging and air flow practically ceasing. When engine temp reaches viscous operating temp the fan should cut in and again blow vast amounts of air.

Whilst the water pump may have failed it's probably more likely to be one of the above especially if the thermostat and viscous coupling are the originals or of an unknown age/condition. It's also a lot easier to check/test these than endeavouring a successful water pump removal/replacement.

Deano :)
Last Edit: 08 Mar 2018 09:50 by Dean and Kaye Howells.

Please Log in or Create an account to join the conversation.

More
08 Mar 2018 16:17 #13 by mort
mort replied the topic: OKA 268 OVERHEATING
Hi Dean,
The viscous hub is not the problem and running with the thermostat removed for a 200klm run home is not an issue either especially if you compare to running with one jammed closed but leaving all that aside you say that 7 psi is the correct pressure for an LT, I am not saying you are wrong but I have gone through the manual and can find nothing to say that so why are you so sure.
I have endeavoured a successful water pump removal/replacement in the past and it is actually very easy.
Martyn

Please Log in or Create an account to join the conversation.

More
08 Mar 2018 19:19 #14 by Ewart and Vivian Halford
Ewart and Vivian Halford replied the topic: OKA 268 OVERHEATING
Mine also has a 7 psi cap

Ewart oka 365
0428911147

Please Log in or Create an account to join the conversation.

More
09 Mar 2018 05:12 #15 by Tony Lee
Tony Lee replied the topic: OKA 268 OVERHEATING
7psi for my XT 123

Tony

Please Log in or Create an account to join the conversation.

More
09 Mar 2018 11:43 #16 by Harry
Harry replied the topic: OKA 268 OVERHEATING
Oka 045 radiator cap is also 7psi
The RMI -25 is a great product I run mine without the antifreeze and live in Yass the people at cost effective maintenance are great to talk to (07) 33766188 250 ml dose 20 liters look it up as it cleans as you drive and even keeps the radiator cooler if you need antifreeze it also works well both it is also on eBay but much cheeper from CEM give it a go cheers

Oka 045 the WIDE Motorhome 6bt cummins 500 watt solar diesel heating gas cooking up grade LSD front and rear diffs to 4:56 from 4:88 . 320 lt fuel 153 lt fresh water in 3 separate tanks 3 house batteries 1 start battery 176 lt upright fridge/freezer Black dog security
Attachments:

Please Log in or Create an account to join the conversation.

More
10 Mar 2018 07:46 #17 by mort
mort replied the topic: OKA 268 OVERHEATING
Hi All,
I have been able to get a spare water pump and will go down with Vince today and replace so if all goes well it will be home by end of day.
Thanks to all that offered assistance especially the spare pump.
Martyn

Please Log in or Create an account to join the conversation.

More
10 Mar 2018 08:45 #18 by mort
mort replied the topic: OKA 268 OVERHEATING
Hi All,
I wasnt expecting the big difference in cap pressure and there is no correct pressure for every oka if you understand how it all works.
The fact that the coolant media heats up it expands which creates pressure and the cap is the relief valve.
As Holmz stated earlier water is the best or very good at heat transfer but over time it will cause corrosion and has a low boiling and high freezing point so we add glycol which has a higher boiling and lower freezing point but is not too good at heat transfer.
A 50/50 mix of water/glycol is the most ideal much more glycol and heat transfer starts going backwards.
Still doesn't explain cap pressure well when water comes to boiling bubbles are created which is an insulation and so reduces heat transfer.
A diesel engine will run efficiently at about ( Perkins/cummins ) 92-94 deg.
Water boils at 100 deg and freezes at 0 deg
A 50/50 water/glycol mix will raise the boiling point about 11 deg which gives more room between operating temp and boiling.
For every psi of pressure you add 2-3 deg of temp to the boiling point.
So a 7 psi cap add 14 deg or 13 psi add 26 deg etc
engine runs at 92-94 deg
water only boils 100 deg
7 psi cap add 14 deg
total 114 deg not a lot of room to move on a hot day or a partially blocked core or fins.

50/50 glycol add 11 deg
15 psi cap add extra 16 deg
total to boil 141 deg a lot of room between operating temp and boiling.

I first asked the question because Vince has 18 psi cap which I considered too high, I would think between 12 and 15 as ideal.
Remember that the info above is considering cooling which is ok in most of australia but we do have cold regions where heating is the concern so a lower pressure cap would be ideal or carry 2 and if you venture in the snowy or tassie use the low pressure and if you go north or desert ( hot regions ) use the high pressure.
So you see there is no correct pressure as such and maybe some especially the XT's that have a rep for overheating maybe its just the cap or water/glycol mix that your using.
Martyn

Please Log in or Create an account to join the conversation.

More
10 Mar 2018 13:37 - 10 Mar 2018 13:38 #19 by Holmz
Holmz replied the topic: OKA 268 OVERHEATING
I went by OKA parts on Friday as Dean slotted me in with the departure south happening.
The cap is a 7psi.

His felllow (Riley maybe?) pumped up the system to 15 psi, and the reticulation dripper started working out of the lower radiator hose (I think)...
Dean was on the wheeled luge sled and tightened it up before I could get bent over to see, but it looked like the right area.
I thought of Vince's hose clamp, so some aspects were similar.
Last Edit: 10 Mar 2018 13:38 by Holmz.

Please Log in or Create an account to join the conversation.

More
11 Mar 2018 07:27 #20 by mort
mort replied the topic: OKA 268 OVERHEATING
Hi All,
Went down with Vince and a spare pump, got the old off and new on in no time.
The problem was as expected where the impeller had come loose sort of in fact the shaft had sheared off for no apparent reason. I found no sign of damage or siezed bearing that could have caused it.
Martyn

Please Log in or Create an account to join the conversation.

Powered by Kunena Forum