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comanche overheating at highway speeds


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Runs around 205-210 around town but keeps climbing to 220-230 on highway...new waterpump new 195 thermostat new expansion tank with volvo cap..any ideas why its overheating? Also the radiator hose coming from the water pump is new and doesnt have the spring in there could it be that its collapsing at high rpms and restricting coolant flow?

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Does it only happen when driving?  If so, the lower rad hose may be collapsing from the suction of the coolant.  The hose has wire spring inside to prevent it from collapsing.  If the spring has rusted away, there is nothing to hold the hose shape.

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In this situation usually means mech fan clutch is failing/failed.

 

Just the opposite. When the fan clutch is failing, the engine will overheat when stopped in traffic and cool down when moving.

 

 

yep...it runs like 200 when stopped in traffic and idling in park will even drop down to 180

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Just an FYI, I wasn't able to find a replacement lower hose with the spring in it when I replaced my hoses about a year ago. I tried NAPA, Autozone, Oreilly's, and no one even listed a replacement with the spring, according to some info I found on the net, the new hose design doesn't require a spring, FWIW my replacement hose without the spring has been just fine. Is your radiator in good shape?  maybe a quick trip to a radiator shop can verify if it's semi plugged?

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Try the simple things first.

 

I had an issue with the radiator cap not holding pressure.  Replaced that and things got better for a little while.  Next replace the thermostat with a fresh Stent 195 degree one.  After that I have to wonder how old is your water pump?

 

When the truck gets warm/hot and you park the truck - Do you see any water/coolant on the ground?  Try getting it warm, then parking the truck with the engine off for 45 minutes.  See if you have a leak, maybe from the water pump?

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Just an FYI, I wasn't able to find a replacement lower hose with the spring in it when I replaced my hoses about a year ago. I tried NAPA, Autozone, Oreilly's, and no one even listed a replacement with the spring, according to some info I found on the net, the new hose design doesn't require a spring, FWIW my replacement hose without the spring has been just fine. Is your radiator in good shape?  maybe a quick trip to a radiator shop can verify if it's semi plugged?

 

 

Try the simple things first.

 

I had an issue with the radiator cap not holding pressure.  Replaced that and things got better for a little while.  Next replace the thermostat with a fresh Stent 195 degree one.  After that I have to wonder how old is your water pump?

 

When the truck gets warm/hot and you park the truck - Do you see any water/coolant on the ground?  Try getting it warm, then parking the truck with the engine off for 45 minutes.  See if you have a leak, maybe from the water pump?

 

Replaced cap with new volvo cap the water pump is also new put in a new 195 stat from napa 2 days ago also just finished putting in a spring in the lower radiator hose still overheating I'm trying a flush right now if that doesnt work then i'm guessing i need a new rad?

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I had overheating issues as well with my 90 I6. I drilled a small hole in the top side of the thermostat. I've seen where they say do both

top and bottom. It also needs to have the air bled properly. I installed a later model thermostat housing with the hole for the temp

sensor. I installed a bleed valve into that hole (C#*@ valve???) You can do a search. If you don't find anything let me know and I will see what I can find for you. Mine is a bit different than the one on CC site. Solved my overheating issues except when I'm sitting in traffic.

I'll probably do the electric fan upgrade at some point.

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If you've done all that and it's still getting hot at speed...and...if you have not swapped out the radiator, I'd vote new radiator.  I resisted advice that my radiator was shot, did everything else, no change.

 

After all, I had a three year old CSF 2 row all metal radiator with only about 20K miles on it, it couldn't be bad. 

 

Bought a Spectra OE replacement radiator, plastic tanks, plastic petcock, new cap and all. For $110.  Never had another problem with cooling.  2 years now.

 

P.S. I bought the CSF from radiator barn and tried to cash in on the warranty...but the warranty is no good if the place is out of business.

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CSF. Chinese Substandard Fabrications.........

Darn right, I'm surprised with the popularity of the XJ/MJ there aren't any good reputable U.S companies making them :hmm:

 

 

They can't compete with the Chinese and the Mexicans.

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The above radiator is $200.

 

RockAuto sells a C.R.A.P. radiator for $63.79 plus freight.  (C.R.A.P. = Chinese Replacement Auto Parts).

 

It just depends on how many times you want to get stuck doing the same job over and over again.

 

Us Old Pharts here learned after the Third or Fourth time...Buy the good stuff, do it right one time and move on the the next problem.  Then fix the next problem the Right way with the Good Stuff.  Your car/truck/what ever will be much better for it. 

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The above radiator is $200.

 

RockAuto sells a C.R.A.P. radiator for $63.79 plus freight.  (C.R.A.P. = Chinese Replacement Auto Parts).

 

It just depends on how many times you want to get stuck doing the same job over and over again.

 

Us Old Pharts here learned after the Third or Fourth time...Buy the good stuff, do it right one time and move on the the next problem.  Then fix the next problem the Right way with the Good Stuff.  Your car/truck/what ever will be much better for it.

I put one of these FFD radiators in almost eight years ago. Haven't run hot since.

 

I used to use Modine radiators. They used to be one of the best you could buy. Now all they make (or have some foreign outfit make) for our trucks is a $100 aluminum single core unit with plastic side tanks. Probably a C.R.A.P. too.  :shake:

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There used to be a few reliable names for radiators, heater cores and evaporators. Those companies have other merged, been bought out or started outsourcing to china. Hard to know who's the good name in the market place because so many are reboxed/renamed across the stores and online.

I paid at bit more for the 92 cherokee radiator 6-8 years ago when the OE radiator finally gave up the ghost. I forget who we got it from but it doesn't matter because they could have folded or outsource now.

 

Just thought I would mention another for overheating cause is a clogged catalytic converter can cause overheating, but it's probably the radiator in this instance.

I knew of someone who almost killed a new motor because the cats were clogged. It started overheating on the highway, seemed ok in town. Thinking back on it I'm not sure they would have know the difference if it wasn't ok in town... Anyway it just a thought as to cause.

 

 

 

 

 

Sent from my iPhone using Tapatalk Pro

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For what it is worth I looked up who we got the radiator from, it was Vista-pro 436020 "with max cooling" ( guess that's their term for towing package) all metal

Cost $187 in 2010 dollars .

Rock Auto doesn't even list them any more. Summit used to stock it but list a new part # sum-382012, that supposedly interchanges with the vista-pro #. looks all metal. Cost $270.

Edit: fits 91-01 XJ & 91-92 MJ

 

Sent from my iPhone using Tapatalk Pro

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There used to be a few reliable names for radiators, heater cores and evaporators. Those companies have other merged, been bought out or started outsourcing to china. Hard to know who's the good name in the market place because so many are reboxed/renamed across the stores and online.

I paid at bit more for the 92 cherokee radiator 6-8 years ago when the OE radiator finally gave up the ghost. I forget who we got it from but it doesn't matter because they could have folded or outsource now.

 

Just thought I would mention another for overheating cause is a clogged catalytic converter can cause overheating, but it's probably the radiator in this instance.

I knew of someone who almost killed a new motor because the cats were clogged. It started overheating on the highway, seemed ok in town. Thinking back on it I'm not sure they would have know the difference if it wasn't ok in town... Anyway it just a thought as to cause.

 

 

 

Sent from my iPhone using Tapatalk Pro

Brand new catalytic converter so thats another cause eliminated waiting to swap out the rad....also i have a question maybe dumb but do you think a bad oil pump can cause ur engine to overheat?..I'm thinking less oil circulation more friction?..just a thuoght

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