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Discussion Starter · #1 ·
yesterday my upper radiator hose connector broke off and I replaced it filled it up with coolant and now the upper radiator hose gets really hot at normal temps while the lower hose is cold maybe and gets warm not hot or anything... I see some steam coming off the radiator but i think its all the coolant that splashed on it yesterday from the hose busting off and flooding it basically. the car does not overheat at idle or driving or anything so I am curious to what it could be
 

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so your car is not over heating and you fixxed the leak. whats the problem? the steam coming off?

as to why your hoses are different temps. maybe the thermostat is not opening since it so cold. that's normal-ish... i think. but if there was something wrong, wouldn't it be safe to assume it would over heat.
 

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You have an air bubble in the rad. Both hoses should be hot enough that holding the lower hose for more than 5 seconds gets to be too much. The lower will be cooler as thats the purpose but when sitting, the lower will match the temp of the upper hose till the fans kick on. You may need to burp the system. Do the fans kick on? If not you need to burp it. lots of DIYs on that
 

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Discussion Starter · #4 ·
how would i do this on a 99 jetta. when the car is warming up i can see some very light steam come off the radiator where the upper radiator hose connects. should i just bleed the coolant out and fill all of it back up again?
 

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First:

Do the fans cycle on and off at running temperature? If not you have air in the rad and the temp sensor for the fans will not read hot enough to cycle the fans.
Step 2 will be to see if the coolant reads higher than the normal 90C/195F. It should not do this.

If this is the case,

Your going to try and massage the upper and lower hoses with the engine running from cool with the coolant reservoir open(gives ample time to do this but you may end up doing it several times). By Massage I mean grab it with your full hand and squeeze it and let go. do this several times on each hose. You may see some bubbles come up in the reservoir. if not, keep "kneeding" the hoses till the lower gets much warmer. Your essentially trying to hand force coolant through the rad to dislodge the air.

It may help to rev the motor to 2000 rpm and hold it to get the waterpump moving faster and forcing the coolant around. This will help dislodge the air in the rad.

If your more visual, try and find a video with someone doing a coolant flush/burp of a mk3 or mk4 vw as the coolant systems are very similar.

A good writeup to read is here

step 9 in the following DIY
http://faculty.ccp.edu/faculty/dreed/Campingart/jettatech/coolingmaint/index.htm
 
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