Checking radiators

a_kelley

a_kelley

mechanical fixer
Joined
Jan 26, 2010
Location
Rutherfordton
Anyone know any tricks to check to see if a radiator has clogged tubes other than removing the tanks? I recently did the head gasket on my xj and it's running hot at extended idle and lower speeds. Initially thought it was lean due to being ported (it was, but not enough to cause the over heating entirely. It did contribute, but not a ton), but since I'm thinking it's not circulating enough through the radiator. It's maybe 3 years old at most, but that doesn't mean anything. Always had antifreeze run in it except if a hose blew like caused the hg to fail. I may just replace it and see (under warranty). I've seen them clog on systems that hadn't had anything but the factory fill AF in them.. kinda tripped me out, being it looked like paper almost clogging the tubes. Not sure what caused that except for old antifreeze breaking down. I do need to reflash it with a xj cal since the zjs don't have electric fans.. got it wired to a switch presently.. it's not quite so likely to get hot if I'm not running the air conditioning is why I'm thinking it's the radiator.. though I guess there's a possibility the head I put in was cracked but didn't see any.. maybe I'll leak it down tomorrow.
 
I would assume you’ve checked the obvious but just in case, start with the basics to rule out the simple things.

1) fan shroud intact? Makes a big difference.
2) fan clutch? Typical failure
3) air filter good?
4) 100% sure there is no air in the system?
I only point those out cause I myself have overlooked some simple things before and created a lot of extra work over something much simpler than I thought.

I like to flush a radiator with a little compressed air too so it really forces the water their to push things out.
 
1- no shroud, damaged core support, won't fit.

2- clutch ok, fairly new

3- not sure, but I'm not lean anymore.. but clogged a/f would make for rich condition?

4- full. Heater hoses looped with Curved hose due to the shut off valve breaking, though it's under warranty, it wasn't but 6mo old. Wish they still made them out of brass.

I've proved a garden hose flow will go through 2-3 tubes with the rest plugged solid on a rad I dissected post replacement.. same with air over water filled....
 
Use and IR temp gun or a temp probe if you have access to one, across different spots of the radiator as it warms up. Look for cool spots. Should be gradually cooler across the rad in direction of flow.
 
Not quite following your answers, so, What is the mileage? Things to check, Radiator hoses can collapse on the inside, thermostat, water pump. I think you said your heater core & hoses, are by-passed, so that shouldn't be a problem. Using or mixing the wrong antifreeze, can cause a clog. Same with stop leak. [You mentioned some kind of scale] I've seen some radiator shops that "thought" they could tell if the rad was flowing, but the amount of water they could pass through it. One of the Best cures I've had on my V-8, was a Flow-cooler water pump. If there is a blockage in the Block, none of the other "checks" will cure that! You changed the head. Could you have gotten the / or a wrong gasket?
Somehow a water passage got covered or stopped up?
 
Correct head gasket was used, block appeared free of rust/clogs, as well as the head. New thermostat, heater is bypassed. Radiator is only 2-3 years old, always had clean coolant in it. I can't really see into the radiator but what I drained out didn't have any particles in it. (It was water from when the heater valve broke since she was running like crap with water getting in the cylinders. Definitely combustion gases were getting into the cooling system, however I'm not certain that running it that way for about 3 weeks didn't contribute some crap into the system.. just basically trying to get ideas on ways to check if the flow is being restricted without having to either swap it out or destructive inspection. Only reason I think it may be partly clogged is because it runs at normal temp when ambient air temp is cooler but starts climbing in the heat of the day with the AC going z it's fairly rapid. AC off takes 2-3 times longer. Also when driving down the road, temps will drop back to normal.. I've not ruled out a cracked head, though I didn't visually see any cracks in it but that doesn't mean much. Really ought & need to pull plugs and do a leak down to rule that out.
 
I would install/ fabricate some kind of shroud. Low speed and idle depend on fan to move air and with out shroud you are only cooling about 1/2 the radiator
 
I was going to suggest a water pump issue, but since I saw that you're not running a shroud....I'd be more inclined to say that's the issue almost entirely. It's not pulling air through the radiator like it should. It can pull from all around and isn't cooling as well as it should.
 
Following up, installed shroud, it self clearanced. Much cooler AC now. Hadn't idled it long enough to see if it'll run hot, much cooler running though. Jury out for now, but thinking it was the issue.
 
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