68’ FJ40 overheating dramas

[Living in the Past]

I would buy a cheap laser thermometer and check the engine and radiator all over to see where its heating up the worst. $25 at harbor china.

If you look at his location not sure if Harbor Freight delivers there. Been in contact years ago with a member who lived on a Station in Western Australia. Pretty remote. A former member wanted to trade a stamped Land Cruiser bezel for a H55F 40 series top cover. He lived in Queensland and said he knew of a friend who had a wrecked Land Cruisers with one. Took months before the member was able to get it. Communication was slow and it required a barge ride out of the area as the first step. Those didn't happen regularly. Unfortunately turn out the piece was off an HJ47 trayback which only had four speeds. My summer home is forty miles away from the closest grocery store. But compared to parts of Australia it's not even close to being rural.

 

[South Texas 97]

Do you have a block drain - it might be worth opening that and seeing what comes out.
Sitting in the drivers seat it is on the LHS at the rear of the block.

 

[Living in the Past]

Do you have a block drain - it might be worth opening that and seeing what comes out.
Sitting in the drivers seat it is on the LHS at the rear of the block.

He has already done that. Are you talking drivers seat on a left side? OP is in Western Australia and assume RHD.

 

[12hT1986]

I am about 2 and a half hours drive from the nearest town (3 if I am in my 60 series) but I’m pretty confident I should be able to track down a digital thermometer most towns out my way are very industrial because of all the mining.

In terms of looking at engine temps I felt the top and bottom radiator hoses felt exactly the same to the touch… I would have thought the bottom hose should be cooler at least by a little bit? So this tells me that the issue is the radiator?

 

[12hT1986]

Right, so this morning I switched radiator caps over from another FJ40 with an F145 and original radiator that sits on 80*C all day regardless of driving techniques

I found that the engine temp took a LOT longer to get up to operating temperature, every morning I go around the same paddock checking cows with the vehicle and it would have been at least 20 degrees cooler by the time I got about half way compared to yesterday with the original cap, at first I thought I had fixed it..

However by the time I got back it was sitting at about 95*C which in my opinion is way too hot from just gently cruising around a paddock on a cool morning especially with no thermostat installed

Out of curiousity I felt the top and bottom radiator hoses and both felt exactly the same temperature to me, a bit hard to say without a digital thermometer. I would have thought the bottom hose should feel at least somewhat cooler?

I had my hopes up for a bit there!
Appreciate everyone’s input

 

[45Dougal]

Do you have a heater fitted and where is it connected in the system? Sounds like you have low flow.

I've seen a few people mistakenly linking the two heater pipes together when removing the heater, which can allow water to bypass the radiator.

Similarly, if its plumbed in close to the water pump in a non-original way then this could do the same (when its switched on).

Does switching the heater on/off make any difference?
Do you have the right pulleys on everything? Belt routed correctly?

Both water pump gaskets installed correctly?

Maybe some photos will jog some memories

 

[12hT1986]

Do you have a heater fitted and where is it connected in the system? Sounds like you have low flow.

I've seen a few people mistakenly linking the two heater pipes together when removing the heater, which can allow water to bypass the radiator.

Similarly, if its plumbed in close to the water pump in a non-original way then this could do the same (when its switched on).

Does switching the heater on/off make any difference?
Do you have the right pulleys on everything? Belt routed correctly?

Both water pump gaskets installed correctly?

Maybe some photos will jog some memories

Heater has been completely removed and I have blocked it off with a bung screwed into the top of the head where the coolant outlet used to be
Belts and pulleys are all as they should be, I think the water pump might be the next thing to point the finger at but when I had the hoses disconnected from the radiator and I started the engine, the pump would spit the rest of the water from the block out of the top hose which indicates to me that the pump is working

I have heard of water pumps ‘cavitating’ whatever that means…

 

[South Texas 97]

Sitting in the drivers seat was just to give an orientation - the left hand side of the engine, is still the left hand side. It doesn't matter if it is LHD or RHD.....grin

I ran my truck with the radiator cap off for about 15 minutes until it got up to temperature and then burped the top radiator hose, got a couple of good bubbles of air, but it really did not drop the fluid level all that much.

Cavitation is just air bubbles forming on the back side of the water pump impeller vanes as it spins, and yes it would certainly reduce efficiency.

 

[pb4ugo]

Did you ever do anything with the exhaust? I also wonder if running no T/stat could contribute to the problem. The water may not be in the rad long enough to cool it. A 50/50 mix of water and A/F will cool better than just water. I do understand not wanting to waste $ on A/F if there's a more serious problems with cooling system. You've swapped in an engine that has run properly and cool when it was installed in another vehicle, I wonder if there's an issue with one or a couple of parts that you added that were not original to the vehicle that it came from and are from the fj40. Such as the water pump or other parts.

 

[12hT1986]

Did you ever do anything with the exhaust? I also wonder if running no T/stat could contribute to the problem. The water may not be in the rad long enough to cool it. A 50/50 mix of water and A/F will cool better than just water. I do understand not wanting to waste $ on A/F if there's a more serious problems with cooling system. You've swapped in an engine that has run properly and cool when it was installed in another vehicle, I wonder if there's an issue with one or a couple of parts that you added that were not original to the vehicle that it came from and are from the fj40. Such as the water pump or other parts.

After todays experimenting I think I’m starting to lean towards the water pump as it’s the same one I used on the old engine

 

[12hT1986]

Did some more experimenting today
Unbolted the hot dog, I am nearly certain that it isn’t the issue as it isn’t crushed and I can see directly through it and there’s nothing obstructing the flow of exhaust, all I achieved was scaring all the kangaroos away

The coolant temp reached it’s usual mark by the end of the paddock check, about 95*C. We are only about a week or so away from winter so ambient temperature shouldn’t be an issue

After I finished my paddock run I took it for a drive facing into the wind with both thermo fans turned on, and the temperature dropped to about 82*C

I turned around away from the wind and turned thermo fans off, and idled in first gear down the road for about 10 minutes before coolant temp reached about 95-100*C

I then turned around again back into the wind, turned both thermo fans back on and drove it as fast as I could, and by the time I reached the end of the road coolant temp was at 70*C

So do I have an air flow issue? I really don’t think so as the original rad fan is sucking in plenty of air and even more with the thermo fans on. I have even cut a couple of vents in the bonnet above the radiator fan to let the hot air straight out the top.

My theory is that the water pump isn’t circulating the water around fast enough at low speeds, the water pump on the engine is the same one I used on the previous engine, and mabye I have overlooked a smaller impeller size, broken teeth on the impeller or something stupid like that.

The investigation continues

Thanks again everyone for your suggestions

Kris

 

[45Dougal]

Sounds like a very likely candidate

 

[12hT1986]

Did you ever do anything with the exhaust? I also wonder if running no T/stat could contribute to the problem. The water may not be in the rad long enough to cool it. A 50/50 mix of water and A/F will cool better than just water. I do understand not wanting to waste $ on A/F if there's a more serious problems with cooling system. You've swapped in an engine that has run properly and cool when it was installed in another vehicle, I wonder if there's an issue with one or a couple of parts that you added that were not original to the vehicle that it came from and are from the fj40. Such as the water pump or other parts.

When I ran the previous engine I tried putting the thermostat back in which I tested in hot water, didn’t make any difference unfortunately
Took the exhaust off today and also made no difference

 

[Suntreemcanic]

Have you checked the lower radiator to see if it is collapsing? There should be a spring inside it.

 

[12hT1986]

Have you checked the lower radiator to see if it is collapsing? There should be a spring inside it.

Haven’t checked for collapsing I presume you mean the rad hose, I know there is no spring inside the hose but I will check for collapsing next time

 

[Suntreemcanic]

Yes I meant the lower radiator hose. A good strong water pump can collapse a lower hose and restrict coolant flow. Open the hood and rev the engine by hand at the carburetor and you can see if the hose is collapsing.

 

[12hT1986]

Yes I meant the lower radiator hose. A good strong water pump can collapse a lower hose and restrict coolant flow. Open the hood and rev the engine by hand at the carburetor and you can see if the hose is collapsing.

So if I check for this and find that the hose doesn’t collapse when the engine is revved, that should indicate the pump is no good? As I know for a fact there’s no spring in the lower hose

 

[Suntreemcanic]

Do not read more into the test, you are testing the lower radiator hose. I do not know how you test a water pump except replacing it with another one.

 

[12hT1986]

Do not read more into the test, you are testing the lower radiator hose. I do not know how you test a water pump except replacing it with another one.

I think that will end up being this weekends job, I’ll reinstall the original water pump that came off the 2F. It was never leaking but the bearing was a little tight. Do you know if I could swap bearings from the one that’s on the engine now?

 

[Suntreemcanic]

Just check the lower hose to see if it is collapsing before you do anything else. A good rule of thumb is only do one "test" at a time.