Radiators - how to check they are workin - Dezzy
Hi,

Not sure my radiator is working okay. The top pipe that goes into the radiator gets hot after a run. The bottom pipe attached to the radiator is cold. Equally, the top end of the radiator is hot and the bottom end cold.

Does this suggest a blockage in the radiator or is this how radiators work, (ie pumps in hot water from the top where it is then cooled by the time it is released through the bottom pipe).

Cheers
Radiators - how to check they are workin - Dynamic Dave

auto.howstuffworks.com/cooling-system6.htm
Radiators - how to check they are workin - Peter D
If your temp gauge is OK and the car is running fine then there is no problem. What you describe is normal operation of the radiator. Regards Peter
Radiators - how to check they are workin - Dezzy
Thanks,

I was getting worried because I was told that all the radiator and all pipes should be hot which proves the cooling system is running properly. As mine was half and half I presumed a blockage in the radiator.
The temp gauge seems stable but the bottom end of the radiator and pipe are v. cold compared to the top.
Radiators - how to check they are workin - Dynamic Dave
but the bottom end of the radiator and pipe are v. cold
compared to the top.


That's exactly as it's meant to be. Hot water gets passed back to the top of the radiator; it then gets cooled## as it filters its way though to the bottom; then the cool water is fed back into the engine.

## Cooled either by air being blown through it if you're in motion; or sucked through it by the cooling fan (only when the water reaches a certain temp, which is determined by a switch) if you're stuck in traffic.

If you click on the link in my earlier post, it explains all of this.
Radiators - how to check they are workin - Cliff Pope
< or sucked through it by the cooling fan>

Usually blown through from the front nowadays, with electric fans ?
Radiators - how to check they are workin - blank
Sorry to disagree with the rest of you, but I don't think the bottom of a car radiator should be cold. A few degrees cooler than the top, yes, but should it not still be about 90 degrees C?

Maybe I'm wrong!

Andy
Radiators - how to check they are workin - borasport20
I'm with andy on this one. on a warmed up engine i'd expect the bottom hose to be cooler than the top one.

I'd be suprised if it would be cool enough to touch safely, let alone cold.


I have to grow old - but I don't have to grow up
Radiators-how to check they are working - Pugugly {P}
Been through this trauma...keep an eagle eye on coolant level and temp guage, if there a mad fluctuations in eithr have it checked.
Radiators-how to check they are working - Railroad
Don't overlook the thermostat as this may well be the problem. When the engine is warm and the thermostat is open the top hose should be warmer than the bottom hose, but not by that much as coolant returning to the engine would be too cool if it was. The idea is to maintain a constant even temperature as far as possible.

You don't say what car it is, most thermostats are fitted in the flow to the radiator, but some are fitted in the return (near the water pump). In either case the bulb points to the hottest part, ie engine side.

If you even suspect the engine is overheating the thermostat must be renewed. The wax will get too hot and go runny, it will then seep out and the thermostat will not work properly. This may be why your radiator doesn't warm up evenly.

Faulty thermostats cause overheating,
Overheating causes faulty thermostats.

Also make sure the cooling system is bled and anti-freezed properly.
Radiators - how to check they are workin - king arthur
Yep, the water being returned to the engine shouldn't be cold - otherwise why would you need a thermostat?
Radiators - how to check they are workin - Dezzy
Hi,

The radiator in question is on a Renault Trafic panel van which has been converted to a camper van. It is a 2.1 diesel.

It isn't actually over heating but I will be spending three months in Spain travelling in it so I was doing all the pre checks before I set off.

If the cooling system was blocked or faulty, would it overheat in a matter of minutes. What are the symptoms over than the temp gauge rasing to the top.

Cheers
(Am I just paranoid ???)
Radiators - how to check they are workin - Cyd
I agree with DD - it sounds like your cooling system is behaving exactly as it should.

Under steady state conditions the thermostat will open just enough to allow some water to circulate thro' the rad', be cooled and returned (coldish) to the engine. It is not necessar for all of the water to circulate through the rad - the engine has several other sources of heat loss, the rad just supplements these to provide exactly the right amount of cooling according to prevailing conditions.

Given that you're going to a hot climate for some time it might nevertheless be wise to invest in a cooling system flush and coolant replenish.
Radiators - how to check they are workin - Cyd
Additional info:

Go on a run (10 miles) - park with the front of the vehicle close toa wall (or otherwise sheltered from the wind). Leave it idling with the heater off. After a few minutes (anything from 5 to 15) the cooling fan should come on for a minute or two. This tells you the fan is okay. Now lift the bonnet and feel the bottom hose - you should feel it get warmer before the fan comes on again (no air flowing thro' rad = no cooling). This tells you water is flowing okay.
Radiators - how to check they are workin - Dezzy
As there are no signs of over heating, I've decided to leave it alone. I was told that if a heavy diesel was going to overheat, it would do so after 5 mins. Presume everything is okay, (fingers crossed), and just being paranoid.
Radiators - how to check they are workin - Cyd
Leaving it alone isn't necessarily the best thing to do. From another thread we learn the vehicle is 11 years old with 48k up. Do you know when the coolant was last changed? You should be changing it every 2 yrs (unless you're using long life antifreeze so it could be up to 5 yrs). If the antifreeze is significantly older than it should be, you may be prone to internal corrosion which basically means you are storing up for trouble. Internal corrosion cuts the cooling efficiency dramatically - going to a hot climate will increase the likely hood of this causing an overheating problem or leaks or both.
Radiators - how to check they are workin - wemyss
I agree with cyd that it is working exactly as it should.
Both my diesel cars are quite cold at the bottom of the rad and I would expect it be so.
Unless the engine was working very hard the thermostat will not be opening very much. However in Spain with higher temperatures you will no doubt find it is much hotter at the bottom end when you stop to check.
I also notice with my diesel cars that going up steep hills the heater gets considerably warmer showing that little heat is generated on normal running with a diesel.
alvin
Radiators - how to check they are workin - racingkarts
i thnk the work COLD is being harshly misused here - the word you are looking for is cooler, that is to say cooler in relation to the top hose.

a good way to check is first visually - no holes, funny green/white patches - and no water (well duh !!!) - also, when the car is at normal operating temp, use the palm of you hand to check for any "hot spots"

thirdly, check the water - should be a misty colour - dependant on anti-freeze/coolant.
Radiators - how to check they are workin - racingkarts
if u want to get really technical - if u susspect a leak, but have no idea where - get some uv dye - and a uv bulb - the rest is childsplay
Radiators - how to check they are workin - Dezzy
Hi,

The coolant was changed a few weeks ago when the timing belt was changed, (they had to remove the radiator to get to it). I bled it last night - no air in the system.

Didn't realise the complications of radiators - glad I asked. !!!
 

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