kirvis Posted March 15, 2011 Share Posted March 15, 2011 Today i'changed the thermostat because it as only blowing cold air. filled it up with the water, had i drive around, but nothing it was still blowing cold. then i went to work about 12 miles. and realized the temp gone up to red. came back home, put the old thermostat back in, but still the same. than i removed the thermostat, but it sill overheats!!! what can be the case? could this be the water pump? but its not making any noises or anything p.s. water hoses are rock hard and it seem only the top half of rad is hot and the bottom is just a bit worm help please [sAD][/sAD] Quote Link to comment Share on other sites More sharing options...
Nic Posted March 15, 2011 Share Posted March 15, 2011 Possible air lock in the system or the radiator cap is leaking and needs replacing. Quote Link to comment Share on other sites More sharing options...
scotty71 Posted March 15, 2011 Share Posted March 15, 2011 I have a spare OEM used rad cap you can try mate.... was fine I just replaced it with a Greddy one Quote Link to comment Share on other sites More sharing options...
Scott Posted March 15, 2011 Share Posted March 15, 2011 That's a lot of coolant changing It's a bit of a PITA to bleed the Supra bud, it has to be done right though or what you are seeing will happen more often than not. Quote Link to comment Share on other sites More sharing options...
kirvis Posted March 15, 2011 Author Share Posted March 15, 2011 Doesnt seem thats the cap as there is high pressure inside. Once i opened the cap it just shooted out. How to get that air out? i kept pressing all the pipes for about 10 minutes with no luck :-( Quote Link to comment Share on other sites More sharing options...
scotty71 Posted March 15, 2011 Share Posted March 15, 2011 Just found this off dnk if its an airlock Let the car cool down, take the rad cap off and run the car with heater on full hot, keep running the car with the rad cap off whilst slowly topping up the system, you will lose some coolant out the rad cap, this is mostly the air escaping from the system, once the car is at its operating temp raise the revs to approx 2000 rpm still with the cap off, you will lose a little coolant so top it up as you go, this is the best way to shift an airlock in the system. Keep checking the heater as when the air lock moves it'll blow hot then top up the rad and fit the cap, then re fill the expansion tank approx half full. There is no need to drain any coolant you already have in there !! Quote Link to comment Share on other sites More sharing options...
Scott Posted March 15, 2011 Share Posted March 15, 2011 Do the above, but add a hill into the mix. Parked on a hill, facing upwards, makes it a faster/easier process Quote Link to comment Share on other sites More sharing options...
scotty71 Posted March 15, 2011 Share Posted March 15, 2011 aha yes I had heard of people parking up a hill while doing this.... thought they were just nutz Quote Link to comment Share on other sites More sharing options...
kirvis Posted March 15, 2011 Author Share Posted March 15, 2011 Ill try to put the thermostat.back in and do the process up the hill ;-) Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted March 16, 2011 Share Posted March 16, 2011 I think its the water pump, the half hot/half cold rad is a bit of a clue. I had exactly the same thing on my brothers n/a Aristo, combination of the water pump and the thermostat Quote Link to comment Share on other sites More sharing options...
Shane Posted March 16, 2011 Share Posted March 16, 2011 I think its the water pump, the half hot/half cold rad is a bit of a clue. I had exactly the same thing on my brothers n/a Aristo, combination of the water pump and the thermostat Trouble is when you get the dreaded airlock the pressure when it does start to cook prevents the water from circulating anyhow and then you do get the half/hot half cold. Not saying to rule out the waterpump as I too have had a couple of tussles with them in the past, but as it was running ok with just a cold heater before the change I would go with the airlock, in my experience they are bad for airlocks, although some time back I read a post from CW who said in his opinion the supra didnt suffer from them. The hill method together with the gradual top up works for me everytime now though. Reckon your heater matrix is the most likely ause of blowing cold. Teres loads on here about that too, I had one that responded well to a blow throw with a hose pipe, all manner of crud got flushed through. Quote Link to comment Share on other sites More sharing options...
Dnk Posted March 16, 2011 Share Posted March 16, 2011 I didn't use a hill Worked very well on a flat level workshop floor on 4 mkiv's. As to the ops problem i'd guess if its the old original rad it could be blocked. Quote Link to comment Share on other sites More sharing options...
Scott Posted March 16, 2011 Share Posted March 16, 2011 I think its the water pump, the half hot/half cold rad is a bit of a clue. I had exactly the same thing on my brothers n/a Aristo, combination of the water pump and the thermostat A big fat ass airlock will do the same thing though I had this very same problem when I changed the coolant on my car. The temp would soar up, then gently come back down, then soar up. Sometimes it would stay hot, sometimes it would move up and down. Half an hour on a hill had the problem sorted Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted March 16, 2011 Share Posted March 16, 2011 But even if there was an airlock the water pump would still be moving water round the engine and therefor the rad wouldnt be half n half, wouldnt it? Im only going on my experience with similar symptoms Quote Link to comment Share on other sites More sharing options...
Dnk Posted March 16, 2011 Share Posted March 16, 2011 I'd pop the bottom hose off the rad and pour water in from the top to rule out a blocked rad Quote Link to comment Share on other sites More sharing options...
kirvis Posted March 16, 2011 Author Share Posted March 16, 2011 There is no need for that is its enough to press the bottom hose to see if water comes.out of the rad. In my case it does Quote Link to comment Share on other sites More sharing options...
Dnk Posted March 16, 2011 Share Posted March 16, 2011 (edited) Okay then thats good as it rules out the rad, follow my bleeding route and you should be fine unless there is another problem. I'd fit a new o/e rad cap as this is a regular thing to go wrong. It could be seized or blocked hence your hoses are pressurising, mine dont go rock hard Edited March 16, 2011 by Dnk (see edit history) Quote Link to comment Share on other sites More sharing options...
kirvis Posted March 16, 2011 Author Share Posted March 16, 2011 Im actually doing it now ;-) Quote Link to comment Share on other sites More sharing options...
kirvis Posted March 16, 2011 Author Share Posted March 16, 2011 The temp is fine at the minute but it still blows cold air Quote Link to comment Share on other sites More sharing options...
Dnk Posted March 16, 2011 Share Posted March 16, 2011 Can you get a new cap on it straight away, if you bleed the system then fit a faulty cap you'll be back where you started as the cap wont let the coolant in and out of the system as it heats up and cools down. Quote Link to comment Share on other sites More sharing options...
Dnk Posted March 16, 2011 Share Posted March 16, 2011 The temp is fine at the minute but it still blows cold air Are you getting air bubbles out the rad ? Quote Link to comment Share on other sites More sharing options...
kirvis Posted March 16, 2011 Author Share Posted March 16, 2011 Are you getting air bubbles out the rad ? Not any more no Quote Link to comment Share on other sites More sharing options...
Dnk Posted March 16, 2011 Share Posted March 16, 2011 Okay, try raising the rpm to around 2000 then let it drop to tickover then repeat a few times, keep topping up the rad. Hopefully this will help shift the air lock at the matrix Quote Link to comment Share on other sites More sharing options...
kirvis Posted March 16, 2011 Author Share Posted March 16, 2011 Aha some bubbles show up ;-) Quote Link to comment Share on other sites More sharing options...
kirvis Posted March 16, 2011 Author Share Posted March 16, 2011 Engine ir running for about half an hour now and the temp is fine but warm air comed out Quote Link to comment Share on other sites More sharing options...
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