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#584868 - 09/05/06 09:30 AM Diagnosing a clogged radiator
MaximaGuy Offline


Registered: 09/20/03
Posts: 704
Loc: Austin, TX
I have replaced the lower and upper radiator hoses and the thermostat but don't seem to understand why my car heats up in uphill freeway driving, gets worse with the AC turned on.

Is there a way to diagnose a clogged radiator? When the car is running with the fans on, the upper radiator hose is full of pressure but then the lower one isn't -- meaning there is hot coolant being pushed into the radiator but not going back via the lower hose back to the enigne.


Is this a sign the radiator is clogged -- I do flushes every 2 years and this time the flush may have flushed the whole sendiments out and clogged the coolant lines..

Any ideas as to the next step in the debug!!!

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#584869 - 09/05/06 09:40 AM Re: Diagnosing a clogged radiator
labman Offline


Registered: 03/14/03
Posts: 8711
Loc: Nothern USA
There was a time when you could put your hand on the radiator. You could shift it around and if parts were hot and others cooler, you knew part of it was plugged up. Don't know what the chances are of doing that on most modern cars are. Watch the fan if you try it at the back.

The lower hose is always going to have lower pressure than the upper. Some of them have a wire coil inside to keep them from collapsing due to the suction.

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#584870 - 09/05/06 10:34 AM Re: Diagnosing a clogged radiator
bdcardinal Online   content


Registered: 06/03/05
Posts: 6487
Loc: Santa Barbara, CA
does your vehicle run lean? i have sean a car that is trending towards lean have the same symptoms.

you could try using an infared thermometer to get a general idea if the radiator is working.

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#584871 - 09/05/06 11:30 AM Re: Diagnosing a clogged radiator
Dan4510 Offline


Registered: 05/19/03
Posts: 2363
Loc: Texas
Take the radiator out and take it to a radiator shop for a flow test, will tell you what you need to know, which is probably a new radiator.

Lean might be a problem too, but if that was so you most likely would get a code for it.

I use RMI-25 in all my cars to keep the sedimentation down and not have this problem. It will actually clean a system slowly over time too so no sediment will exist to flush out and clog up the engine.

Dan

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#584872 - 09/05/06 01:02 PM Re: Diagnosing a clogged radiator
MaximaGuy Offline


Registered: 09/20/03
Posts: 704
Loc: Austin, TX
Also since changing the thermostat I am loosing coolant. In the sevice manual for a maxima they don't mention using those liquid gaskets which installing a new thermostat. In my case there was a metallic gasket which was very thin -- don't know if that will surfice to get a good contact between the block and thermostat.

Also, the manual does not mention using thread sealants for the thermostat screws. Do I have to go back and remove the thermostat and use the liquid gasket and seal the threads?

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#584873 - 09/05/06 03:04 PM Re: Diagnosing a clogged radiator
Oil stain Offline


Registered: 08/30/04
Posts: 125
Loc: Lakeland, FL
Did this over heating start after replacing the thermostat? If so, the thermostat may have been put in backwards.

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#584874 - 09/05/06 06:50 PM Re: Diagnosing a clogged radiator
CBDFrontier06 Offline


Registered: 04/26/06
Posts: 1979
Loc: Dallas, TX
You may be experiencing the same problem my best friend had with his El Dorado...the core actually collapsed, blocking off flow. He couldn't even drive across town before overheating. I can't imagine a clog causing your lower hose to be cool...sounds more like a collapse to me.

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#584875 - 09/05/06 07:07 PM Re: Diagnosing a clogged radiator
MaximaGuy Offline


Registered: 09/20/03
Posts: 704
Loc: Austin, TX
The chances of a collapsing lower hose is remote since I just replaced then with Gator hoses. Isn't there a simple way to determine a clogged radiator... now, when I drain my coolant it comes out clean, no particles, no oil strains etc.

I am leaning towards a faulty indicator switch too. Yesterday while driving within the town the mechanical gauge was higher than normal, it falls on its own to normal, climbs back a notch, climbs really high on uphill highway drives.

These cooling systems ought to be made simpler.. sucks.

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#584876 - 09/05/06 07:35 PM Re: Diagnosing a clogged radiator
CBDFrontier06 Offline


Registered: 04/26/06
Posts: 1979
Loc: Dallas, TX
The CORE of the radiator, not the hose.

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#584877 - 09/06/06 09:09 AM Re: Diagnosing a clogged radiator
Drew99GT Online   happy


Registered: 10/11/02
Posts: 20656
Loc: Colorado Springs
perhaps it's normal! Maybe the stat was stuck open when and now the new one is keeping the engine at proper engine temp. Just a thought. Exactly how hot does it get? The coolent level drop sounds like an air purge, which also could have caused the slightly higher temps.

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#584878 - 09/06/06 09:41 AM Re: Diagnosing a clogged radiator
labman Offline


Registered: 03/14/03
Posts: 8711
Loc: Nothern USA
I doubt it is normal. A system should have enough reserve capacity that the temperature doesn't go on a hill. I doubt a flaky sensor would just happen to go up on the hills too.

With the engine cold, could you remove the bottom hose and pour a bucket of water into the top? I would think you would get a fairly good stream out of a good radiator.

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#584879 - 09/06/06 03:15 AM Re: Diagnosing a clogged radiator
Oil stain Offline


Registered: 08/30/04
Posts: 125
Loc: Lakeland, FL
Does your system have any bleeders to let the air out? Sounds like you can have trapped air in the system. Try getting the front end of the car higher up, like parking on a hill or with jack stands. Do this when the engine is cool so you can open the rad cap and leave it off. Start the car and let it get up to operating temp so the thermostat opens. Run it this way for a few minutes to let any air pockets escape.

Also, if you do have any leaks the car will over heat.

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#584880 - 09/06/06 04:22 AM Re: Diagnosing a clogged radiator
MaximaGuy Offline


Registered: 09/20/03
Posts: 704
Loc: Austin, TX
I have 110K miles on my car and what is the ballpark on radiators getting replaced for whatever reason!!!

The coolant intake from the overflow tank has reduced significantly.

BTW, the air pockets were relieved by opening the air relief valve while I replaced the thermostat.

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#584881 - 09/06/06 07:55 AM Re: Diagnosing a clogged radiator
labman Offline


Registered: 03/14/03
Posts: 8711
Loc: Nothern USA
I see radiators as a life of the car item. And I am not as careful to change coolant as I should be. I think most radiators that die are killed by topping up a leaky system with high mineral tap water.

If you are going to mess with a leaky system, and least go with a PG based antifreeze.

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#584882 - 09/07/06 09:18 AM Re: Diagnosing a clogged radiator
unDummy Offline


Registered: 02/01/03
Posts: 8756
Loc: RI
Nissans don't burp too well. Several heats cycles are needed. Make sure the recovery bottle is full. When filling, hold the bleeder open until a steady streams exits the bleeder. This should only be done when cold.

What brand thermostat was used?
What year Maxima?

Clogged radiator depends on water used, maintenance interval, coolant used, and flushing method.

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