Jin_Chris

Basic questions about coolant/radiator/radiator cap

It is 97 4Rner 145k miles auto, original owner. well maintained. No problem whatsoever except......

I just recently did 2nd t-belt/waterpump/t-stat/spark plug, hoses and belts etc etc including New Koyo radiator (to be preventative against strawberry milkshake thing...).

It has been back on road and runs good and no problems. But I just noticed that it seems losing coolant a little over about 2-month period. No visible leak, no nothing.... no strange smell or anything. My final suspicion is on cooling system itself... my questions are,..

1. does OEM radiator cap fit Koyo Aluminum radiator?
2. is it necessary to replace OEM radiator cap periodically?
3. if OEM radiator cap is weakened (the spring of inner seal) eventually, I believe it will open the passage to overflow tank "prematurely". right? then, will the coolant get vaporized in normal driving temperature without any visible trace/sign? does this sound feasible scenario?

This 145k and 13 years old OEM radiator cap look just fine at least visually. But if this good looking radiator cap needs replacement "periodically". That means I have to replace those rad caps of all of my other cars in my family (1 bimmer, 1 benz, 1 hyundai, 2 toyota, 1 acuras, 2 chrysler + + .....yes! my big family.... ).

Thank you in advance.

Maj

A leaky cap would cause the overflow tank to have an above normal level. You didn't specify how many times you have topped off the radiator but a complete cooling system drain/refill can sometimes result in air pockets which should work themselves out after a couple of top-offs. Check for a crusty-looking buildup around the hoses and the water pump area - signs of a slow leak. The definitive test is a pressure leak-down test which can be performed at any radiator shop.

Jin_Chris

When new koyo radiator was put in, yes! I spotted crusty build up around lower hose (engine side). I believe I did fairly good job in removing almost all of those build-up and I tighted with 2 hose clamps in that area.

Regarding the level of coolant in overflow tank, I did not observe level being raised up. Actually, it becomes a little lower after each add-up. So far (over 2 month period), I added total approximately 1/2 gallon of coolant (little by little). Then, still it becomes a little lower every week or so.

Maybe, my question can be put in another way... Does the percentage of water in the coolant (50/50 mixture) get vaporized eventually in normal driving temparature?

BigBallsMcFalls

yes but not enough to notice like you are seeing.


you are losing coolant somewhere.
------------------------------------------------------------

taste the water drops out the exhaust pipe. are they sweet ? yes do it. it will not harm you doing this once.
if sweet, there is your coolant leak. headgasket.

(of course spit that out when done)

Irish Death

Might also check you floor inside the rig, see if they are damp after a drive....heater core might have a slow leak?

Jin_Chris

Yuk! hahahahaha.. But that is the sure diagnose method for BHG. But again, I do not believe my rig has BHG issue. I have serviced a few Acura BHG problems. So, I believe I know what BHG symptoms like and and how it was caused... Thank you for your suggestion though.

I will check thoroughly again. As was pointed out first, I rather check the hose connection area if there is any wet spot (where the scale/build-up was removed in lower hose area...).

I still wonder if radiator cap needs to be regularly replaced after X amount of years or miles....

brian2sun

You might want to just replace the radiator cap for piece of mind and because it's pretty cheap anyways. I also suggest getting a small extendable mirror and looking under the water pump and thermostat for coolant trails/stains. Mine had a leaky cooling hose going into the oil cooler which is below and to the right of the thermo (if your at the front of the truck and looking at the engine and assuming you have a 3.4L).

BigBallsMcFalls

true. could be dripping somewhere and evaporating before it falls to ground

Jin_Chris

I am confident that I took care of the area you are talking about (oil cooler to waterpump hose) when I did t-belt/wpump/radiator etc etc service.

I just checked rockauto to get rad cap... there are two choices "stant" or "gates".... which is better? I am thinking both brand names are fairly well known.... I am tossing my coin to pick one... ....

quicksilvr

But you didn't replace the radiator hoses? I couldn't quite tell from your post if you replaced the hoses, or just cleaned them. If you replaced them, then great.


.....but....



If not, that might be your problem. That crusty buildup is from a slow leak, BUT, you can't fix it by cleaning it and putting two clamps on, because it's weeping out through the interior of the hose. When hoses get old, they break down and start weeping through the reinforcement threads. You can clamp it all you want, and it will still leak slowly. Never enough to drip or puddle, but possibly enough to lose as much as you seem to be losing. Replace both upper and lower hoses (they're cheap anyway) and see what happens.

Also check your rear heater lines right where the turn up to go through the floor pan. They might be leaking, but you haven't spotted it yet, because it's so far back on the underside.

Jin_Chris

Of course, I replaced upper/lower rad hoses with brand new shiny OEM's. I also replaced that rusty rear heater lines with metal line. But I haven't crawled back to check those lines hooked to rear heater (right under pass side rear seat...) yet. That is what I actually planning to check this weekend (along with rad cap). Thanks for your suggestion.