Diagnosing a clogged radiator

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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!!!
 
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.
 
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.
 
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
 
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?
 
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.
 
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.
 
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.
 
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.
 
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.
 
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.
 
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.
 
Mine is a 2K maxima with 110K miles on it.

Replaced thermostat with OEM from the stealership and got Gator hoses for the upper and lower ones.

I have always flushed every 20K miles or 2yrs and used distilled water. The air relief valve is in the most "f.cked" place on earth and everytime I do it my blood pressure goes to a new level with a fear that I will drop the valve (it actually is a 10mm screw) in the engine bay and have to search it. As you said, I relieve the air once till there is a steady stream of coolant flowing off the valve. What also irritates me is that the valve is right over the inner CV boots and I bet coolant is not good on those boots, but then the valve is in the most stupid place on earth.
 
You know actually when you talk about coolant, I have only recently started to use the Peak Global coolant, I hope that hasn't stirred up all the rust and dirt out of the radiator and clogged it.

But then when I drain the radiator, it always comes clean with no particles or oil strains.

These cooling systems are way too complicated and beats me (I bet it beats the sh*t out of the techinicans trying to root cause the problem too).

The VW beatles have a century old cooling system and works like a gem with not so complicated gadgetry.!!!
 
I mentioned touching the radiator. Many of them are such a mess now, you are lucky to even see them.

It is getting to where I am reaching more of the scheduled maintenance on my 02 Cavalier. Wonder what kind of a mess flushing the radiator will be? No cap, and the outlet is half way down the side. The thermostat can stay until it fails. May last as long as any after market one. Your new one could have been bad out of the box.
 
The feel by hand test is pretty good - we can't see inside the radiator.
Maybe the water pump impeller blades are slipping, or corroded away. This has tripped me up a few times, when diagnosing cooling problems.
 
Maximaguy,

I'm on my second Maxima (currently a '97 with 114,000 miles), and can say that their temp gauges are very rock steady within their set range. By this I mean that mine will not go over 1/2 way no matter what I do. I've even had my secondary cooling fan (the passenger side one) unplugged for a month in Louisiana's summer while waiting on the part from the dealer. My gauge didn't rise above 1/2 way, even in traffic with the AC on. The only side-effect was my AC didn't blow cold unless moving above 25 mph or so. So yours going higher when going up hills indicates a problem to me.
Have you checked on Maxima.org to see if anyone has had the same problem you are? I believe it was Jime on there that tested the coolant temp in reference to his factory temp gauge with a scan tool. He found that what is normal on our gauge (1/2 way) is actually within a range of somewhere between 160-210 or so. I don't remember the numbers exactly, but normal on our gauge is between a pretty wide spread of temps.
I went through the clogged radiator deal this summer on my wife's '88 Nissan pickup. Everything in the cooling system was changed because her truck's gauge would climb to 3/4's when the AC was on and driving at highway speeds. It didn't do it at idle or with the AC off. Some members here suggested the radiator was clogged and the cooling system wasn't able to keep up with the thermal demands when the AC was on and engine under load. Replaced the radiator (it was the last thing that hadn't been replaced), and it cured the problem. Her gauge is back rock steady at 1/2 way again.
One thing I noticed before changing the radiator in her truck was the coolant didn't seem to be flowing as fast through her radiator as it should have been. Look down your radiator neck and watch the coolant as it heats up. When the thermostat opens, that fluid should start moving through there at a pretty good clip. If it isn't moving forcefully through there, I'd bet your radiator is partially clogged. And like my wife's truck, it'll get worse with time. I even used the chemical flush (a "Super Flush" you leave in for several hundred miles) with no effect.

Hope this helps.

Dave
 
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