Previa Cooling System

August 31, 2006

i have just brought a 1994 toyota previa (uk model) 2.4 petrol automatic no air con with 68,ooo miles on the clock

unfortunetly the radiator has just gone and i am asking if anybody knows how to bleed the cooling system. i understand they are a bit of a pig to do.

very grateful for any help on the subject

cheers mattieb

p.s does anybody know of i will need to upgrade the rad to a heavy duty one as i will towing a trailer tent with the previa a few times a year ?

August 31, 2006

Would get a deep core or double core, about £100 of eBay, when filling the system pour the water in very slowly and when full take for a drive, temp gauge should go up then down, wait for it to cool then top up again....

September 4, 2006

Hi Matt

The header tank has a small hose at the back- difficult to see and even more to get off. While your system is drained take off the header tank and flush out. Make sure the header tank has all the holes clear, especially the one where the little hose joins, mentioned earlier. You may need to poke some wire in the hole to clear it. This little hose is the air bleed from the high point of the engine, with this blocked, you will find it impossible to fill properly and will definitely overheat. Filling slowly is a good idea, but not essential. What is important is that you make sure the heater is purged properly and the system is full and the pressure cap is on before you road test. The way I do this (not the only way) is to fill the system, run the engine with the headlights and heated rear window on (to load the engine) and keep topping up as the level falls. Turn the heater to hotest and keep the fan on first speed- no faster or it wil blow away all the heat you are making with the engine. If your temp gauge says hot and the heater is still cold put on the pressure cap temporarily and rev the engine to 2500rpm for a minute or so. Keep feeling the heater output until it gets warm. Remove pres. cap carefully and top up. Use Toyota coolant not cheap anti freeze. It is formulated for the mix of metals in your cooling system. Be aware that you may have had a leak for some time and when you fix this leak- the pressure will rise and further leaks may occur. You need to check regularly. Hope you get on allright. Cheers Ray

November 27, 2021

Greetings!

Ray99, if you copy, would you please explain how the little “air bleed” hose at the back of the expansion tank works?

I have managed to get around 10litres of coolant into the system- capacity is 11.6litres. And I think there’s an airlock in the heater core as there’s a sloshing sound under the dash when I rev around 1500-2000. This sound is accompanied by largish bubbles coming out of the coolant fill funnel.

the vehicle has been on ramps for the week or so that I’ve tried to fill the coolant . Previously, on the road, it was overheating.

heater is blowing nice and hot.

any advice greatly appreciated.

I’m considering going to get more petrol in a can (for the third time) to continue bleeding by revving a little and squeezing hoses, and allowing the engine to cool with a funnel full of coolant on the expansion tank. But this seems to be taking days and days. Let alone petrol.

should I let it cool with the cap on? I’m slightly worried it will suck everything out of the expansion tank and begin to suck air if the coolant runs out.

cheers