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Cruiser overheats at highway speeds

 
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Old 18 Sep 2011, 08:59 am
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Default Cruiser overheats at highway speeds

Ok first time posting because I've been able to fix most of my problems just by searching the forum. I've got a 2003 non-turbo. 115,000 miles. About six months ago it started running hot (when I say hot I mean the gauge gets to the bottom of the red and I start taking emergency actions) only if I'm at highway speed 70+ here in Florida. If it does, slowing down or getting off the highway brings the temp back down. I can drive around town all day long and have no problems. I always drive with the a/c on but when the car starts running hot the a/c temp gets warmer (not sure if one thing is a symptom of the other).
Yesterday I tested the fan by jumping it to the battery and both speeds work. The fan does come on as soon as I start the car with the a/c on and I know that at if it was a fan issue I'd have more problems at idle than on the highway. I've looked through the grill and don't see anything unusual blocking air flow through the radiator. Drained the antifreeze, flushed with water through a heater hose that I disconnected, replaced thermostat and radiator cap. Refilled with Zerex G05. Bled system through bleeder valve. Ran for 20 mins in the driveway. No problems. Took up to highway, within 7 miles it started getting too hot. Pulled off the highway, car cooled right down. Checked antifreeze levels when I got home and there was no loss of antifreeze.
I've seen posts about bad head gaskets and seen the antifreeze should be tested. Questions:
1: How do you test antifreeze for exhaust gasses?
2: How can you check the head gasket? (I could do a compression test but would that show an issue from water jacket to exhaust?)
3: How can you check the radiator as I've seen posts about them gumming up?
4: Anything else I can check and how?
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Old 18 Sep 2011, 12:52 pm
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Default Re: Cruiser overheats at highway speeds

Might be as simple as a partially clogged radiator. When your running at 70+ the water pump is going faster but if the coolant is being blocked from running around the engine faster to get rid of the heat, your start to overheat. At lower speeds the flow is fast enough.

Are you loosing any coolant? If not, the head gasket should be OK.

At 115K, you might have picked up enough "gunk" to clog up the radiator. You have chnged the timing belt and water pump right? That should have been done at 100K. If not, maybe the water pump is about to give out.
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Old 18 Sep 2011, 04:25 pm
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Default Re: Cruiser overheats at highway speeds

Thanks very much for the reply. Haven't done the timing belt / water pump yet. I do realize I need to. A little background on myself. I rebuilt deisels in the Marine Corps, and owned and ran a dirt track race car (had to rebuild that a couple times. LOL) So I'm very comfortable around cars and tools. It was recommended that I get the car up to operating temp and squeeze the upper and lower radiator hoses to check both firmness and temperature. The top I was not able to squeeze due to pressure. It was very hot and couldn't hold it without a rag. The bottom, however, was not near as hot as I could hold without a rag, and it was not nearly as firm (I could press in without too much effort). It definetly was more firm than if the engine were off, but not nearly as firm as the top. I know there is not coolant in the oil as I know what that looks like. I also know that right around the time this started, my girlfreid hit a tire (darn retreads) that was in the highway and bent the radiator support up about 1/2 inch (I fixed that and there is no sign of coolant loss so I know it didn't BREAK the radiator). When I drained the antifreeze I paid close attention to it and did not notice any gunk in it. Didn't pay as much attention when I ran the water through other than to look to see when it started running clear. Sorry about the lengthy posts, just trying to describe the symptoms as best I can. Thanks for the help. I appreciate any help that anyone can give.
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Old 18 Sep 2011, 04:51 pm
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Default Re: Cruiser overheats at highway speeds

No, the more information the better but I'm not sure where to go from here if everything you said is working. Both speed of the fan, radiator blockage, water pump, thermostat, radiator cap, trapped air in the coolant system, head gasket and the head itself are all the things we've seen on the forum for overheating.
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Old 18 Sep 2011, 05:47 pm
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Default Re: Cruiser overheats at highway speeds

My guess would be a clogged radiator... But if you haven't done the timing belt and water pump yet, it could be a bad pump. I have heard of pump impellers corroding away...
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Old 18 Sep 2011, 06:21 pm
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Default Re: Cruiser overheats at highway speeds

could also be that you may have air still in the system when you did the radiator flush and fill and its causing a coolant flow problem or that the water pump may be ready to go. Although you should seem some seapage from the water pump around the timing cover area.

Remember that once the car starts running hot it will start to burn away at the antifreeze and that could also cause an air pocket.

Twi
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Old 18 Sep 2011, 07:06 pm
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Default Re: Cruiser overheats at highway speeds

Please don't get me wrong, I'm not discounting anything at this point. When I drained the antifreeze, no gunk came out with it, that doesn't mean it's not all messed up. The reason I posted about the radiator hoses is the guy at the parts store told me to check them, and I was hoping the fact that they had different feels would be a clue as to whether it would be the adiator or the water pump. I really don't know as with the race car I would keep the radiator in GREAT shape and when I was rebuilding engines, we automatically replaced water pumps regardless of what they looked like. Which would you guys suspect first given the info that I've given? I appreciate any feedback, and hope that ya'll don't think I was tooting my own horn by "listing credentials". Cause I'm certainly not THAT bright.
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Old 18 Sep 2011, 07:15 pm
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Default Re: Cruiser overheats at highway speeds

Quote:
Originally Posted by TWI View Post
Although you should seem some seapage from the water pump around the timing cover area.

Twi
Not seeing any seapage, but I was told that the impeller shaft could start slipping just before a waterpump gives out completely. Was told it was rare but could happen. I'm really at a loss in this one. Never had a car over heat at highway speeds that wasn't a thermostat, or the water pump leaking so bad you couldn't mistake it. I've also never had a radiator go bad on me. (Been in acidents they had to be replaced it though ). Which do you guys think is more likely?
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Old 18 Sep 2011, 07:27 pm
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Default Re: Cruiser overheats at highway speeds

It's a 2003, did you ever flush the radiator? Chrysler only recommends coolant with HOAT properties. If the wrong coolant is used the inside of the radiator can and does corrode and cause a blockage.

If you've checked the water and oil and don't see any signs of a cracked had gasket letting the water and oil mix, my bet is on the radiator. But something like the impeller of the water pump not getting the coolant to flow correctly isn't out of the question. We're all just guessing at this point.
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Old 18 Sep 2011, 08:20 pm
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Default Re: Cruiser overheats at highway speeds

No one mentioned the following. If a radiator is old enough, and worn enough, the fins that fit between the tubes will loosen and deteriorate. If that happens, the radiator becomes much less effective at removing heat. You can often see that the fins on the top and sides are loose or brittle by running your finger over the fins.
Or take your raditor to a shop and have them examine it.
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