# IH434 Diesel overheating after coolant change.



## stevey (8 mo ago)

My 1970 434 diesel was having intermittent overheating issues. After 5 minutes of driving it would run hot. So I'd leave the tractor parked, idling and the temperature would drop after 5 mins and then I could carry on without it overheating. So I replaced the thermostat with the same type (TC1 bellow as that was in it already, I've also tried a new type thermostat too) hosed out the block and the radiator with a hose pipe, and then refilled with new coolant 50/50 mix. It now overheats really fast, but doesn't cool down. So I changed the water pump, pipes and the belts. Again same symptoms, just overheats quick.
Any pointers as to where to start. I did notice when changing the thermostat and the water pump that there was a real build up of rust internally.


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## mastrkee (May 8, 2017)

Sounds like the radiator cores are plugged with the rust you mentioned inside. It’s possible to have the cores rodded out and cleaned by a competent radiator shop. I hope your able to find one in your area. A through flushing out of the outside of the cores with a pressure washer could help with cooling but I think will only stall the inevitable. There’s also some products available for you to do a chemical flush and back flush of the radiator’s internal core. A little research on the inter web will show you the chemical flush products. Best of luck to you!


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## HarveyW (Sep 15, 2014)

Check also for bubbles in the coolant when it gets hot. Might be a head gasket leak??


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## stevey (8 mo ago)

I did wonder if the radiator was blocked, but whilst the tractor is running hot, the fluid in the radiator is cool, and without bubbles, and when it's running hot the top hose isn't hot as I'd expect.
But once the engine is off, the top hose does get hot, so I know the thermostat is opening up, but doesn't appear to be with the engine on.


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## HarveyW (Sep 15, 2014)

Maybe your temperature sending unit or temperature gauge are defective?? You could try checking with an infra-red temperature sensor.


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## stevey (8 mo ago)

That's a good idea that. I'll get one picked up and try it.
I've no reason to think that the gauge is faulty, but stranger things have happened.


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## Andrew 110 (Feb 20, 2020)

Is there air in your coolant? The other day the farm I work for bought a 7.3L ford and the previous owner had just changed the coolant on it and when I was driving it to the farm after I picked it up it overheated, they never Primed the coolant system so there was air in it and that made it overheat.


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## stevey (8 mo ago)

I did suspect an air lock. What I don't know is how to get rid of it, if there is any. Any suggestions ?


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## pogobill (Jan 31, 2012)

Maybe a vapour lock.... 
I see you've posted as I typed. Had this happen on a truck. Heater blew cold and the truck started to get real hot. I'd let it cool, remove the cap squeeze the rad hoses to see if you get air, then fire it up and observe to see if there are air bubbles or the coolant goes down..


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## pogobill (Jan 31, 2012)

Once it warms up, the thermostat should open and give you full flow as well, while observing.


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## Andrew 110 (Feb 20, 2020)

I opened the radiator cap and squeezed the top radiator line tell the air started coming up, after that I just let it sit tell it stopped bubbling then started the truck and refilled the coolant when it was running.


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## LouNY (Dec 15, 2016)

Or park it facing uphill on a steep grade.
Remove the cap and let her run, watch the temperature gauge and top of the radiator,
the water level should rise a bit as it warms up and when the thermostat opens you should see circulation in the top tank.


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## FredM (Nov 18, 2015)

Have you checked the cooling fins for blockage with grass and debris?.


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## Andrew 110 (Feb 20, 2020)

A second thought is the engine dirty? We have a tractor that over heats if very much dirt gets stuck on the block. And we half to wash it at the end of every day.


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## stevey (8 mo ago)

The block is relatively clean, for a tractor, so I don't think it's that, and the fins of the radiator are clean as I had the radiator off to replace the water pump.
I'm waiting for my infrared temperature gun to arrive to test the theory that it's not really as hot as the dials are telling me.
In the mean time I've got it on some car ramps to get some elevation to the front end - I know it's not great, as living in the flattest part of the UK - Lincolnshire, hills are not in abundance here.
I'm not seeing any bubbling in the radiator still, and the top hose still only gets hot once the engine is off, and not a lot happens by squeezing the top hose either. There just doesn't seem to be any circulation of fluid.


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## stevey (8 mo ago)

So, my temperature gun arrived. I ran the engine for way longer than I dared previously, as the temp gauge was off the scale hot, and monitored the thermostat housing, and at no point did it get above 74C.
So I think I can safely say that my issue is a sensor rather than anything else, so I'll get one ordered.
Many thanks to everyone's contributions.


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## mikegunderson10 (8 mo ago)

stevey said:


> My 1970 434 diesel was having intermittent overheating issues. After 5 minutes of driving it would run hot. So I'd leave the tractor parked, idling and the temperature would drop after 5 mins and then I could carry on without it overheating. So I replaced the thermostat with the same type (TC1 bellow as that was in it already, I've also tried a new type thermostat too) hosed out the block and the radiator with a hose pipe, and then refilled with new coolant 50/50 mix. It now overheats really fast, but doesn't cool down. So I changed the water pump, pipes and the belts. Again same symptoms, just overheats quick.
> Any pointers as to where to start. I did notice when changing the thermostat and the water pump that there was a real build up of rust internally.


I had a similar problem with my pickup. Turn out the bottom 1/3 of my radiator was completely plugged. also try flushing the block backwards. I'm assuming you don't have a blown head gasket? good luck


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## mastrkee (May 8, 2017)

Is there a chance that the thermostat is installed backwards?


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## beauregaardhooligan (Oct 14, 2017)

mastrkee said:


> Is there a chance that the thermostat is installed backwards?


Good call. I remember they also have a loose rivet on the flange of the thermostat that needs to go up if I recall correctly.
I'd recommend taking the thermostat out and see if it acts the same. If so, then it's most likely your radiator clogged.
You can also check for hot/cold spots on the radiator with a temp gun that will indicate clogs.


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## LouNY (Dec 15, 2016)

stevey said:


> The block is relatively clean, for a tractor, so I don't think it's that, and the fins of the radiator are clean as I had the radiator off to replace the water pump.
> I'm waiting for my infrared temperature gun to arrive to test the theory that it's not really as hot as the dials are telling me.
> In the mean time I've got it on some car ramps to get some elevation to the front end - I know it's not great, as living in the flattest part of the UK - Lincolnshire, hills are not in abundance here.
> I'm not seeing any bubbling in the radiator still, and the top hose still only gets hot once the engine is off, and not a lot happens by squeezing the top hose either. There just doesn't seem to be any circulation of fluid.



I'd like to see you repeat running your tractor after removing the thermostat if the water is not circulating you have a problem.
The thermostat housing would not give you a good reading point if it didn't open.
If you are not seeing fluid circulating either the water pump is bad, possibly turning in the wrong direction, the thermostat is bad, the belt is not driving the water pump, or the block or radiator are plugged.
Most thermostat's have either a bypass or a small passage to allow heated water to reach them as the thermostat will not open untill hot water reaches it.


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## drclean (9 mo ago)

they make a wand that will fit in small places to flush out radiator, also mine did the same thing and there was a lot of seeds and grass under the radiator. the wand I saw at a new holand dealer or you could probaly buy on line.


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## Busted Tractor (May 22, 2018)

Once had an overheating issue on a combine, owner requested thermostats, water pump, fan belts. Asked if the radiator was clean "Yep just cleaned it" . Arrived on site started work, checked the radiator -- and could not see thru the fins. Asked customer for a pressure washer - 3 hours later could see thru 99% of radiator. No other parts replaced. Told customer to call if combine overheated. Took a year for him to call about overheating. Had to clean radiator -- again.


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## LouNY (Dec 15, 2016)

Here you go Radiator Genie;
Radiator Genie
they work very well, the air one is good for air cleaners as well as radiators.
When cleaning a radiator if a person uses the air one, then slops some soapy water on followed by the water wand then air again you will be surprised at what comes out.
And if you are feeling real ambitious then use one of the foaming condenser cleaners and follow by another water flush and then a final air it will be fairly clean.
Depending of course how many coolers are stacked in front of each other and how good a job you do.

I don't like pressure washers for this job you can bend over a lot of fins with one real easy.


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## twospeedgearjammer (May 18, 2021)

mastrkee said:


> Sounds like the radiator cores are plugged with the rust you mentioned inside. It’s possible to have the cores rodded out and cleaned by a competent radiator shop. I hope your able to find one in your area. A through flushing out of the outside of the cores with a pressure washer could help with cooling but I think will only stall the inevitable. There’s also some products available for you to do a chemical flush and back flush of the radiator’s internal core. A little research on the inter web will show you the chemical flush products. Best of luck to you!


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## stevey (8 mo ago)

So looks like the issue was the water gauge and/or sensor, reporting the overheating when I fact it was running as expected. Oddly it worked fine before I changed the coolant, then it failed on me after the coolant change, or maybe it was on its way out already. They don't make parts like they used to, only been on the tractor 52 years  
Anyway, swapped the sensor and gauge for £20 and all good.


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