How To Get An Air Lock Out!

[djla]

Hi,

I am glad i have found this site, recently the radiator on my partners previa went, we bought a new radiator and my partner changed it over with no problems and replaced the water and coolant.

That is until he started the car and it seems to have an airlock in the cooling system. The temperature gauge says the car is hot but the air coming out the heater is cold, the water tank also bubbles over and makes a noise like it has air trapped in there somewhere. My partner has been outside for 3 days running trying to get the air out, he has tilted the car, revved the engine, filled up the water tank when it bubbles over and drove the car round the block a couple of times, with no luck! He doesn't really know what to do anymore. I found this site after doing some internet searching and i'm hoping one of you guys (or girls) has any ideas?

Thanks very much.

[propnut]

The refill process on these cars should be done nice and slowly with the front of the car raised, the engine running and BOTH heater knobs on FULL. Also there is a small overflow pipe on the header tank that the car uses to bleed itself but which is notorious for blocking. He needs to make sure this is 100% clear. He also needs to make 200% sure that the thermostat is opening. If the return pipe from the thermostat housing is not getting hot then the thermostat needs replacing. Even after getting the air out he will notice that the next day the level will have dropped, this is normal and it should just be re-topped up and checked for the next few days.

What you have not told us is why he decided to change the rad in the first place. If it was because the car was overheating then the old rad may or may not have been the issue. Head gaskets on these cars blow just like on any other car. The symptoms you have described are also synonymous with a blown head gasket.

Finally at NO point whatsoever should tap water EVER be used in a radiator. He must mix 50/50 coolant with distilled water.

[rob-tdm900]

Hi, I recently changed my coolant as the old stuff had lost its protection.I measured what I took out and replaced with the same ammount, slowly, as propnut suggests. I changed the thermostat at the same time. I now notice that I have no pressure in my expansion tank and the car runs cooler. I have taken the smaller hoses off one at a time and let the water flow out, so I know the pipes are not blocked? I also noticed on a motorway run in the recent cold weather the engine temp was at cold at 70mph? The car heater takes longer to blow warm in the mornings, but it does get there eventually. Any suggestions please??

Propnut, I hope you dont mind me asking but on the "old" site I asked about my previa revving when cold. You gave me some very detailed advice which I cannot find. Is there a way I can access the old forum so I can find the info? I still havent found time to sort it ,but am hoping to in the next week or so, if I can find out what to check. Many thanks, Regards. Rob

[propnut]

Howdy Rob

If you are not losing coolant and the car is not overheating then it just sounds like the cooling system is running more efficiently. HOWEVER, it could also be that your new thermostat is a dud and is stuck open. The needle should get to mid way in at least 3 - 5 miles even in this cold weather. Thermostats should always be tested in a jug of boiling water before fitting to a car. If it is working you should see the needle go to just over half and then suddenly drop to just below that. That sudden drop is the thermostat opening.

Re the old site, sorry but I was just a member on there as I am here. The guy that was running it decided to shut it down due to lack of interest. The simple fact is that unlike our sister cars the Estima's, Previas are just so damn reliable that owners seldom need to frequent forums to resolve problems. As for your problem I have amemory like a sieve and cannot remember what it was. Start another thread here outlining the issue and I will do my best to help you.

[rob-tdm900]

Thanks for that propnut, Shame about the old site, it had so much useful info on. Anyway back to the thread. My car does warm up albeit a bit slower than before and at normal everyday speeds the temp guage sits in the middle (as it has done since I had the car). I was concerned that I dont get any pressure in the system and at sustained motorway speed the guage sat just above stone cold for 3 hours?? I can commute to work (about 30 mins ) and release the rad cap and there is no pressure. I couldnt do that before. Should I be worried? Regards. Rob

[propnut]

It does sound like your thermostat is stuck open. Running too cold is almost as bad as running too hot.

[rob-tdm900]

Thanks for that propnut. Will have a look as soon as the weather improves!