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Overheating 75 series

Tech Talk for Cruiser owners.

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Posts: 70
Joined: Wed Sep 21, 2005 7:24 am
Location: Queenton NQLD

Overheating 75 series

Post by Joombi »

G'day, I searched for about an hour looking for a post about overhearting problems someone had with a 75 series cruiser (1HZ) & couldn't find it so here we go again....
It is fine around town but on the highway it overheats & I remember someone saying about the fan clutch and how it shouldn't matter even if you have a fan at 100kmph but I'm no expert thats why I'm here.
the radiator is brand new & so is the thermostat. what else could it be, thanks......
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Post by known 2 »

if ur fan isn't working it's best, and it still overheats on the highway. must meen maybe the cooling viens/pipes on engine could be blocked or have some gunk in them.

perhaps???

but i'm not sure as i run a thermo fan and no engine fan on mine.
kaylee 2004 hdj78 RV. 33 mickey atz's, winchbar, 3i lift, 3i exhoust, spoties, roofracks and ufh. pimped interior .

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Post by Dane »

Water pump? Your fan is only needed for low speed/stationary work, not at 100km/h. There is some other problem related to the flow of your coolant through your system. If it's not the pump it may be a blockage/restriction of some sort or the thermostat. Why did you replace your thermostat and radiator? If it was running hot beforehand you obviously still have that problem. Test your thermostat by immersing it in boiling water to check that it opens correctly. Failing that, check that your sender and guage are accurate by using another known good set. My Rocky once tricked me into believing that it was running hot but it was just the sender.
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Post by balzackracing »

have you changed anything to do with the front of the ute, bull bar, changed position of number plate etc. a/c condencer's can block up and restrict alot of air flow.
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Post by thomo »

Head gasket , do a pressure test.
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Post by rockcrawler31 »

Tear out your rad and have it checked. should cost less than 100 bucks if you take it to them out of the car. Seriously, even if you think its fine have it checked. I chased my tail for ages trying to source a highway speed overheating problem thinking that a brand new rad would be ok. I was wrong.
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Post by baddboy »

Have yu got any spotties covering the front? Not a very wide opening on the front, if you put spotties in the way it makes a difference. I had the same problem.
Fan will only be an issue around town at slower speeds. At highway speeds fan should be free wheeling. Only other things could be a blockage in rad or thermostat is stuck open. As mentioned a head gasket can cause as well. If you take of the radiator cap at running temp (Carefully) you should ot get any small bubbles!! You can have head gasket leaks checked by rad shop with a testkit, simple and cheap.
I bet you have big spotties though!!!
75 series ute. 8 inch lift, Drop shackles, Shock hoops, ladder bar, Ubolt flip, 3 inch wheel spacers, intercooled turbo, winch, twin detroits, 35" Mtr's, etc, etc.
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Post by Rangie Thing »

I had the same thing happen, and it was the clutch fan on mine ( even at 100km it would over heat as i had to much cap sitting up front.
it started by going up to 3/4 temp then dropping down to normal (did this for about 2 months) then on the way home one day at 100km it got hot.
changed the stuffed clutch fan when i got home and never had a over heating problem again.
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Post by Joombi »

Thanks for your replies fellas, I'll start with the Fan clutch (cos its the easiest) then a Radiator flush & work back.

I replaced the radiator because when I took it in for the 150k service to a mate of mine he pressure tested everything and he exchanged the radiator, thermostat was changed at the same time.

I have a winch & not very big spotties up front (Yet) there was a bug screen so I took this off & made no difference.

I also was told about the injectors overfueling or something but this will be when all else fails, I'm going to get them done in the near future anyway, just want to sort this other crap out first
thanks again
CT
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Post by CT »

Fan clutch for sure is my bet. Chased all this around on my 75 and while radiator cleans (external) helped, hoses and thermostats did nothing. New fan clutch and all was fixed.

Some people say that if you feel resistance spinning them by hand then they're ok. This was crap in my case. I could feel tension even though the unit was stuffed.

Driving home after getting the fan clutch replaced I couldn't figure out why things sounded different. The penny dropped when I realised that it was actually fan noise I could hear (first time ever!!).

While chasing around your cooling system, consider when your timing belt is due. To do a waterpump, the timing belt has to come off. For the cost of the pump vs. labour, do them both at the same time and save $ in the long run.

Cheers
Craig
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