OKA 268 OVERHEATING
- mort
- Topic Author
- Offline
- Posts: 848
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
Please Log in or Create an account to join the conversation.
- dandjcr
- Offline
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.
Please Log in or Create an account to join the conversation.
- Holmz
- Offline
- Posts: 866
Please Log in or Create an account to join the conversation.
- mort
- Topic Author
- Offline
- Posts: 848
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.
- Holmz
- Offline
- Posts: 866
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.
- mort
- Topic Author
- Offline
- Posts: 848
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.
- Holmz
- Offline
- Posts: 866
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.
- Peter and Sandra OKA 374
- Offline
- Posts: 1321
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.
- dandjcr
- Offline
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.
Please Log in or Create an account to join the conversation.
- mort
- Topic Author
- Offline
- Posts: 848
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
Please Log in or Create an account to join the conversation.
- outyonda
- Offline
- Posts: 780
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.
- Dean and Kaye Howells
- Offline
- Posts: 533
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
Please Log in or Create an account to join the conversation.
- mort
- Topic Author
- Offline
- Posts: 848
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.
- Ewart and Vivian Halford
- Offline
- Posts: 440
Ewart oka 365
0428911147
Please Log in or Create an account to join the conversation.
- Tony Lee
- Offline
- Posts: 509
Tony
Please Log in or Create an account to join the conversation.
- Harry
- Offline
- Posts: 166
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
Please Log in or Create an account to join the conversation.
- mort
- Topic Author
- Offline
- Posts: 848
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.
- mort
- Topic Author
- Offline
- Posts: 848
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.
- Holmz
- Offline
- Posts: 866
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.
Please Log in or Create an account to join the conversation.
- mort
- Topic Author
- Offline
- Posts: 848
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.