Bottom Hose Cold, no Heat from Vents

[Jag]

Hi all

I have run into a bit of a problem with my 1999 – Polo 1.4 Auto, 35k miles – Couple of weeks ago I noticed that the temp gauge was dropping when driving at speed and on Idle would creep back up, so I suspected stat. I changed it over last weekend and found the old housing for the stat had a hole where the pin of the stat should be resting against so the pin was not being pressured. I replaced both stat and housing.

The temperature get to normal 90 Degrees and stays there and doesn’t fluctuate like it used to… but I now notice I cannot get any heat out of the vents until I rev the engine somewhat it seems to generate lovely heat when on a run just not when idling. I looked under the hood and found that the top hose is nice and hot but the bottom hose the one leading to the stat is cold. Also had the car idling for a long time but never noticed the fan kick in at all but wasn’t overheating either.. Anyone have any ideas what this could be?

I’m thinking airlock but not sure..

Help much appreciated

Regards

Jag

[alexperkins]

Sounds like theres an airlock in the heat exchanger

The bottom rad hose takes a long time to get hot, and will really only get hot when the stat opens which you have to be driving to cause really.

You may have more than one air lock - Run the engine with the coolant cap removed, and squeeze the bottom and top hoses on the radiator for a few mins (slowish squeezes so as not to suck air in)

Also make sure the heater is set to HOT when you do this as itll help flow the water through the heat exchanger

Did you replace the coolant aswell?

[Jag]

Alax - Thanks for the reply. I just drained the coolant when changing the stat, from the temp switch and topped it up again. I didn't run the engine with the coolant cap removed so will try that today. Also will squeeze the bottom hose and have the heater setting on max.

[Jag]

Having tried all the suggestions I'm still in the same situation. I removed the filler cap and ran the engine and squeezed the hose didn't get much release of air. I let it idle like that for a while. but it was taking too long to get the temperature to 90 so took it on a run but again the bottom hose was still cold..

any more ideas I could try?