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possible one more solution for overheating jimnys

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07 Feb 2023 08:23 - 07 Feb 2023 08:38 #247400 by slaxh
 
Hi everyone, I'm bothered by overheating too for months, after many attempts, I found a possible solution.
Before the modification, it overheats easily in urban traffic which made the AC down. I have tried to refill the visco fluid of the fan, also get the radiator fins cleaned, and there's still no any effect. The highest coolant temperature recorded is 114℃ and intake air temperature is insanely as high as 81℃. That is very tough in such hot summer in my city, in which ground temperature often goes above 40℃.

The solution is to increase the water pump rotating speed to improve the circulation.

The diameter of the original water pump pulley is about 113mm. I replaced it with a custom made 100mm one (the belt is also changed to a shorter 4PK815S), so the rotation speed is increased by 27%.

After that, I have not experienced even once of overheating. The coollant temperature is around 82-86 (max 89). I have left the thermostat as stock one. I think it is capable with the increased throughput.

The drawbacks of this modification is the weight. The custom-made pulley weights 200g more than the stock one, which is said to have potential more stress over the bearing of the water pump. But no more overheating is the best result for me.
 
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Last edit: 07 Feb 2023 08:38 by slaxh.

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07 Feb 2023 08:30 - 07 Feb 2023 08:39 #247401 by slaxh
The pulley in the picture:The left one is the stock water pump pulley. The right one is custom-made one which have 100mm in diameter.
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Last edit: 07 Feb 2023 08:39 by slaxh.

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07 Feb 2023 13:40 #247406 by DrRobin
Interesting idea, I can see how improved water flow would help at low revs, but at higher speed the limiting factor is likely to be the radiator, or more specifically how fast you can get rid of the heat from the radiator. The problem is if you are pushing the hot water through the system faster, it has less time in the radiator to loose the heat.

A bigger fan or one that runs faster/all of the time would help and may be a bigger radiator.

2011 Blue Jimny SZ4 morphing in to a 2020 SZ5 in the next week or so.

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07 Feb 2023 13:54 #247408 by mlines
At high speeds you may even experience cavitation around the pump vanes which would reduce flow and even wear out the vanes.

I would wonder whether the water pump was worn out already

Martin

2003 M13 early KAP build.
3" Trailmaster lift with 1.5 Spacers on front
Customised winch bumper and roll cage
235/85R16 Maxxis Bighorns on 16" Rims, 4:1 Rocklobster, Rear ARB locker and on-board air
Corrected arms all-round, rear disks, Recaro seats and harnesses

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26 Nov 2023 08:55 #252390 by Phaeton
Is/has there ever been an option to run an electric fan, never been a lover of viscous coupled fans.

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26 Nov 2023 09:14 #252393 by rogerzilla
If the water pump mod is on a well-used Jimny, the chances are that there are other problems causing the overheating, like a blocked radiator. It's a fairly inefficient engine and does need to dump a lot of heat for its size.  On the plus side, a Jimny warms up very fast from cold - my Mazda 3 SkyActiv-X takes almost 10 miles to warm up, just like a diesel does.

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26 Nov 2023 14:43 #252396 by jackonlyjack
Mine spends 80% of its time off road
Meaning it runs for long periods at less than 10mph. so I fitted these vents which reduces engine bay temperature 
 
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