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Joined: Sun Jan 06, 2019 5:35 pm
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Vehicle: 1975 LJ50 2 stroke

Post Posted: Sun Jan 06, 2019 5:47 pm 
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Hi all,

Brand new to all this forum business so bear with me

I have a 1974 LJ50 with the 2 stroke water cooled in it. It is by no means a restoration project or a licencable vehicle, just something I am hoping to use for shooting. it was sitting in the shed for 11 years until I pulled it out and got it going. It runs well, but I have had a hell of a time trying to figure out why it won’t cool properly. I have had the radiator done up, new water pump, fixed a leaking head gasket, taken the thermostat out and flushed the engine 4 or 5 times. Lots of alloy corrosion came out the first few times I flushed the block (which I presume was from the old head). It does not use any water. It will stay cool idling and driving quietly around the paddock but if I cruise it down the road, the temp shoots up again straight away.

Is there anything I am missing here? Any help would be greatly appreciated!
Thanks

Kris

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Joined: Tue Apr 20, 2010 12:00 am
Posts: 2064
Location: Georgetown, Guyana
Vehicle: 98 5 dr SQ420, 05 5dr JB420

Post Posted: Mon Jan 07, 2019 12:16 pm 
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What does "have had the radiator done up" mean?

What you're describing sounds like the cooling system being unable to get rid of the heat produced by the engine doing any meaningful level of work - which would suggest the radiator is not up to the task, either because of a lack of coolant flow, or air flow - if the vehicle is "cruising" there will typically be enough forced air flow that a fan is not required, so that suggests the radiator is clogged - either internally or externally.

Have you tried running it without a thermostat - do this for testing purposes only as operating without a thermostat can cause other issues.

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az supporter
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Joined: Thu Aug 20, 2009 12:00 am
Posts: 2319
Vehicle: LJ50V, SJ70

Post Posted: Mon Jan 07, 2019 1:19 pm 
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Silly question, I suppose, but you haven't fitted the fan on back to front? You will see an "F" on the side that faces forwards. The fan will go on the wrong way round and will then try to push air out forwards through the radiator. This will work OK when idling, but as soon as you move, the airflow will cancel out the flow from driving.

There is absolutely nothing complex about the 50 cooling system, however there was a change between the '74-'75 models to the '76-'77. If you have mix and matched parts on your '74, you could run into problems. The early system did not have coolant running through the intake manifold unless the heater tap was turned on (the thinking being that if you did not need to heat the interior, there was no need to preheat the air-fuel mix. The late system constantly preheated the intake manifold, and there was an additional tap to turn on the interior heater. The plumbing on the 2 systems are different. Also, the early system ran an 88deg thermostat, while the late system used an 82deg as it had a larger volume of coolant that was constantly hot and circulating. (BTW turning on the heater tap in either system will give you an additional "Radiator", the heater, that's if you can bear the heat in the front seats!)

And finally, check your ignition timing. Too much advance can cause overheating.

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Joined: Sun Jan 06, 2019 5:35 pm
Posts: 3
Vehicle: 1975 LJ50 2 stroke

Post Posted: Mon Jan 07, 2019 3:24 pm 
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Hi fordem and 303zuke

I have taken out the thermostat as it was no good, and have cut out the middle of another old one ( the valve in the middle) and i have the “skeleton” of one in there for some restriction. Is this ok to do? I know it’s not as good as a thermostat though.

By having the radiator Donne up I mean I sent it away to Geraldton to AdRad to be rebuilt. It was fairly full of corrosion and the fins were falling out. It looks brand new now and doesn’t seem to be blocked up, if I take the bottom rad hose off and put the hose down the filler it runs out well. Also, I did check the fan before as I thought that was the problem. The ‘F’ is facing towards the radiator. Which I presume is correct. I am not sure if this has been tampered with and changed over the years, but there is a hose coming from the head that goes over to the rear end of the intake manifold, and another that goes from the front end of the manifold to the water pump. There are no taps anywhere. Also 303zuke when you mentioned about mix and matching parts, the head i put on is off an LJ50V. If that matters at all.

Thanks

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az supporter
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Joined: Thu Aug 20, 2009 12:00 am
Posts: 2319
Vehicle: LJ50V, SJ70

Post Posted: Tue Jan 08, 2019 5:00 pm 
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Image[/img]

The Heater Tap is the large threaded outlet on the head. If your vehicle is a Paddock Basher/Shooting Buggy, maybe you don't have a heater and this has been blocked off.

Image
[/img]

Image
[url=https://flic.kr/p/2e1rnGS][/img]

The car will DEFINATELY run cooler with a thermostat than without one. Sounds strange, but true. There are some weird items offered on Ebay as LJ50 thermostats, correct item is Tridon TT239-185.

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Joined: Wed Mar 05, 2008 11:00 pm
Posts: 290
Location: Waikerie

Post Posted: Tue Jan 08, 2019 5:27 pm 
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Never run a motor without a thermostat ... ever!

Have you checked that the temperature gauge is accurate?

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Joined: Sun Jan 06, 2019 5:35 pm
Posts: 3
Vehicle: 1975 LJ50 2 stroke

Post Posted: Tue Jan 08, 2019 11:46 pm 
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The hose that is supposed to go through to the heater that has the tap on it like in the picture, bypasses the heater and goes straight to the intake manifold on mine. There is no tap on the fitting that holds the hose
on, I presume it is off something else. The outlet that is supposed to go to the inlet manifold, is plugged off with a bung. This shouldn’t make
much difference should it?

When I get some free time I will play with the timing and see if I can track down a thermostat.

Thanks for all the help

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Joined: Wed Mar 05, 2008 11:00 pm
Posts: 290
Location: Waikerie

Post Posted: Wed Jan 09, 2019 7:28 am 
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Kris P. wrote:
The outlet that is supposed to go to the inlet manifold, is plugged off with a bung. This shouldn’t make
much difference should it?
this is stretching the memory gland a bit but I think that needs to be flowing .. part of the overall circulation of the system.
Heater is irrelevant, that is always just a bypass and can be blocked off with no issue.


... will do some digging and see if I can find my workshop manual ... ...

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az supporter
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Joined: Thu Aug 20, 2009 12:00 am
Posts: 2319
Vehicle: LJ50V, SJ70

Post Posted: Wed Jan 09, 2019 10:05 am 
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Kris P. wrote:
The hose that is supposed to go through to the heater that has the tap on it like in the picture, bypasses the heater and goes straight to the intake manifold on mine. ... This shouldn’t make much difference should it?


Image[/url]https://flic.kr/p/2e747Ca[/img]


Either way, it should be OK and not contribute to overheating. Setup A would be ideal but Setup B would work too, just not as well. Setup B will be exactly the same as the early factory setup with the heater tap turned off, with no preheating of the inlet manifold. Not optimal, but works.

I think your issues will be the thermostat or timing.

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