# Radiator hose questions



## Nissan0301 (11 mo ago)

so I've been noticing the top radiator hose is getting to about 185* and the lower no more than 75-90*. Doesn't seem to be overheating according the the gauge and I've used the IF gun on it. Can I remove the thermostat in the water outlet without giving up heat temporarily or does that control heat? Lol, if the water isn't circulating where is it going? He overflow doesn't look overfilled..

It's kind of hard to verify which one is stuck without removing it and testing. I would assume it would just be best to replace both at the same time.


----------



## VStar650CL (Nov 12, 2020)

It's never a good idea to run without a 'stat, although on most cars you can tinker the temperature +/- 10F or so without hurting anything. Cylinder wall wear at 90F is about _eight_ times greater than 180F, so running "cool" isn't really a good thing. Running at the _right_ temperature is a good thing.

What you're seeing at the hoses is 100% normal, it means your radiator is doing its job. Hot water from the block and head comes out through the 'stat into the upper hose, is cooled off as it passes through the radiator, then returns to the engine through the lower hose. So the outlet tank and lower hose on the radiator will always be _much_ cooler than the inlet tank and upper hose. That will also be true for a blocked radiator, but that would cause overheating. Since your engine isn't running hot, the temperature difference means the radiator is working you're basically thinking something normal is a problem.


----------



## Nissan0301 (11 mo ago)

The flow of coolant wasn't happening either when I had the radiator cap off and watched it. I let it warm up from cold to warm (4 bars on temp) and it just overflowed out of the radiator some. Not in a flowing motion more like slow rising. I'm going to go out to double check the coolant flow in a little.

thank you for the information. I found my
Service manual and your information was correct.

the reason I thought it was a stuck thermostat is because I thought the flow was the opposite way, I guess it didn't matter since it wasn't actually overheating.


----------



## VStar650CL (Nov 12, 2020)

They'll usually bubble up if you have the cap off during warmup, just because the fluid is expanding from heat but there's no flow until the 'stat cracks open. Most cross-flow Nissan radiators have baffles underneath the cap anyway, which makes any flow hard to see. Touch and feel will usually tell you more than a visual. The upper hose will start to get hot before the 'stat cracks because a small amount of hot coolant is migrating through the bleed ("burp hole"), but it will get too hot for comfort in a rush as soon as the 'stat cracks open. If the radiator is healthy and you touch the fins, you'll be able to feel the heat migrating across the tubes into the outlet tank. That's the easiest way to identify a plugged radiator. Because the plug is limiting the flow and not the thermostat, there will be little or no "hot rush" when the 'stat opens, just a gradual increase in the heat even with the 'stat full open.


----------

