creative Posted May 3, 2008 Share Posted May 3, 2008 Right gents. This is doing my head in now. The car has been randomly overheating but I have started to narrow things down. The car has a new rad in it, I've just changed the viscous fan today and left the car to idle for a good half hour as I did some other jobs and nothing, temp doesn't move past the halfway point. stat I'm guessing works fine as its getting upto temp in a reasonable time. You can see the flow of water through the top of the rad, so I presume the water pump is working. All good so I set off to work. my journey involves a bit of town driving, 30min motorway then a bit of town driving again. All going fine, pull of the motorway, temp still at half way. Halfway through the second part of town driving i notice the needle starting to rise. I get the car to work and the needle is not at overheating stage but close to it. I pop the bonnet and check the pipes etc which are firm and both pipes are hot. I release a bit of pressure out via the rad cap and start the car up again and the needle drops to 3/4 point and doesn't move. I sat at idle for 10 mins at the needle doesn't move up or down. The only thing I can think of is the rad cap isn't working as it should. Is the run on the motorway causing the system to over pressurise and not being able to escape which in turn is causing it to overheat. the rad cap is an aftermarket trd jobby, so I will be ordering a new one on tuesday to rule that one out, but could it be as simple as something like that? cheers gents Quote Link to comment Share on other sites More sharing options...
ShamelessTT Posted May 3, 2008 Share Posted May 3, 2008 Dont the TRD ones force the system to a higher pressure (1.3bar)? stresses everything out a little. Have you tried changing the thermostat, there cheap as chips. Quote Link to comment Share on other sites More sharing options...
creative Posted May 3, 2008 Author Share Posted May 3, 2008 Dont the TRD ones force the system to a higher pressure (1.3bar)? stresses everything out a little. Have you tried changing the thermostat, there cheap as chips. the rad cap states 1.1bar on it. haven't changed the stat as I cant see that being the problem as it doesn't overheat any other time except when I come off the motorway. might as well get one though just for the sake of it... Quote Link to comment Share on other sites More sharing options...
Supra ST Myster Posted May 4, 2008 Share Posted May 4, 2008 is the bottom pipe going to the rad getting hot? if it is the the stat is working. Quote Link to comment Share on other sites More sharing options...
Soonto_HAS_soop Posted May 4, 2008 Share Posted May 4, 2008 I wouldn't necessarily trust the standard temp gauge to pick up little fluctuations, when I had mine, it would stay at the centre point for at least 25 degrees. I put in an HKS aftermarket gauge that was far more accurate. Quote Link to comment Share on other sites More sharing options...
creative Posted May 4, 2008 Author Share Posted May 4, 2008 is the bottom pipe going to the rad getting hot? if it is the the stat is working. yeah bottom hose is hot.. hence me ruling that out. Only thing I'm not 100% on is the rad cap... I wouldn't necessarily trust the standard temp gauge to pick up little fluctuations, when I had mine, it would stay at the centre point for at least 25 degrees. I put in an HKS aftermarket gauge that was far more accurate. these aren't little fluctuations mate. The temp is gradually rising to overheating. I know they arent the most accurate guages but these are major temp changes. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted May 4, 2008 Share Posted May 4, 2008 I'd put a new stock cap on it, and a new stock thermostat. That should cover it unless you have combustion gasses getting into the coolant. Quote Link to comment Share on other sites More sharing options...
creative Posted May 4, 2008 Author Share Posted May 4, 2008 I'd put a new stock cap on it, and a new stock thermostat. That should cover it unless you have combustion gasses getting into the coolant. that was my plan. dont think its combustion gasses as the coolant doesnt smell of it. its just strange how it doesnt do it everytime I drive it. Drove it home after work and nothing... even had a run around at normal town driving for half an hour and the guage didnt move. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted May 5, 2008 Share Posted May 5, 2008 Perhaps test the sender unit or replace it? Quote Link to comment Share on other sites More sharing options...
creative Posted May 5, 2008 Author Share Posted May 5, 2008 Perhaps test the sender unit or replace it? hmmmm... hadnt thought of that. Did another test today, temp was fine for about 2 hours then started to overheat again. took it home and had a play with the rad cap, released some pressure and the temp dropped down to halfway again and was fine as I left it to idle as I washed it. No signs of gasket failure so im not worried about that....(just yet!) not experienced symptoms like this before so scratching my head at the mo! Quote Link to comment Share on other sites More sharing options...
creative Posted May 7, 2008 Author Share Posted May 7, 2008 right. Had a sniff test done and nothing showing there (thank god!) but I think we have found the problem... or rather 3! First is the viscous fan is weakening. I have swapped it for another one but that one is also in the same condition so looking at a price for a brand new one now... hence why it was taking a while to overheat and not doing it all the time. Second was the rad cap. It wasn't sealing on the radiator properly and when it was, due to the over heating it wasn't venting out at the pressure it was meant to..now replace with a new one from MrT. Thirdly, the reason why the rad cap wasn't occasionally sealing properly was due to it being bent by the bonnet when it is closed. There is a indentation on the bonnet lining exactly where the rad cap sits. so hopefully with a new viscous and the bonnet lining removed it should (?) cure it. Quote Link to comment Share on other sites More sharing options...
Homer Posted May 7, 2008 Share Posted May 7, 2008 Stock rad cap is the way to go. Strange that your "TRD" one had 1.1 stamped on it - the TRD cap is 1.3bar. Faulty copy maybe? Where did you buy it from? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted May 7, 2008 Share Posted May 7, 2008 As the rad cap fouls the bonnet can I assume it's a none stock rad? Or a none stock bonnet? I guess rad, as I have never seen a none stock bonnet with a noise attenuation lining like the stock one. Quote Link to comment Share on other sites More sharing options...
creative Posted May 7, 2008 Author Share Posted May 7, 2008 Stock rad cap is the way to go. Strange that your "TRD" one had 1.1 stamped on it - the TRD cap is 1.3bar. Faulty copy maybe? Where did you buy it from? no idea... was on the car when I bought it. Got a new stock one on now... for free! As the rad cap fouls the bonnet can I assume it's a none stock rad? Or a none stock bonnet? I guess rad, as I have never seen a none stock bonnet with a noise attenuation lining like the stock one. Im guessing its a non stock rad as the car has had a front end bump and its got a new rad on it. Having not seen a stock rad yet im only guessing the bonnet is definitely stock though. Quote Link to comment Share on other sites More sharing options...
Homer Posted May 7, 2008 Share Posted May 7, 2008 Are you able to post a picture of the rad? Was the previous owner a member? Something is certainly amiss here Quote Link to comment Share on other sites More sharing options...
creative Posted May 7, 2008 Author Share Posted May 7, 2008 Are you able to post a picture of the rad? Was the previous owner a member? Something is certainly amiss here yeah i could do. will take one in the morning. The car wasnt registered as accident damaged but It has had a quick fix on it to make it right to sell... i knew this when I bought it as its not a problem for me as I intend to respray it etc etc. its just its timing! be glad when this week is over tbh and the car was previously les's.........so yup... it from the forum. altho when it went off the radar for 2 years is when I think most of the damage has been done. I got it at a very good price so I'm not complaining yet! Quote Link to comment Share on other sites More sharing options...
creative Posted May 14, 2008 Author Share Posted May 14, 2008 right ... this is doing my head in now! I have tried 3 viscous fans, 2 rad caps, removed the stat all that is left is the water pump. Rad is cool at the bottom end pipe and hot at the top pipe....as should be and I can see water flowing over the top of the rad when the car is running. I found a slight split in the heater matrix to head pipe so have removed that and bypassed it (matrix is dead on mine) and this helped me run a lot longer. I thought it was cured but on the way home after about an hours drive of both city and motorway driving the temp started to rise again. Pulled up at home and opened the bonnet and turned the car off. It started bubbling from the expansion tank which is usually a sign of the rad cap but I know it isnt as that is brand new. the only other thing I can think of is I have another split in another hose somewhere as this will cause the same symptoms as the rad cap not sealing. your opinions please gents.... I know someone will say change the waterpump but I really dont have the funds at the moment due to having no job and too me it seems to be working fine. Quote Link to comment Share on other sites More sharing options...
ShamelessTT Posted May 14, 2008 Share Posted May 14, 2008 Maybe the rad isnt holding pressure? i had bubbling etc when my rad had a tiny hairline crack in it. (Its new i know tho so unlikely unless its a duffer and failed compression tests.) Quote Link to comment Share on other sites More sharing options...
creative Posted May 14, 2008 Author Share Posted May 14, 2008 i now definately think its a cracked pipe somewhere. went out for a drive to the folks house which is about 15 - 20 miles away, nothing, Nada, not even a flicker on the gauge. I stripped it all down when I got there, flushed the rad and the block, double checked the pump and that's working fine. re assembled and after bleeding left it to idle whilst I did a few other things. 1 1/2 hours later I pack up and drive home get within half a mile from home and the gauge starts going up.... f*$^&**ing thing! Parked up at home popped the bonnet and turned the car off. it starts to bubble in the expansion tank so I have a play with some of the other cooling pipes like the ones to the TB... the bubbling stops!! I turn the car back on and the guage is back at half way. I think this is why its been intermittent. I think the engine is moving just enough to open a crack or hole up and this is causing to draw air in and not seal correctly... so my job for tomorrow is to remove the smaller cooling pipes and see what condition they are in... I will not be beaten by a lump of metal!! Oh and it was good driving it again! how do you guys cope when its in the body shop for months at a time??!! had a massive grin on my face all the way home... Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted May 14, 2008 Share Posted May 14, 2008 Pressure in the system is higher than ambient, so if there was a crack Id expect water to come out rather than air in... Correct me if Im wrong. Quote Link to comment Share on other sites More sharing options...
creative Posted May 14, 2008 Author Share Posted May 14, 2008 Pressure in the system is higher than ambient, so if there was a crack Id expect water to come out rather than air in... Correct me if Im wrong. It's like the bubbling from the expansion tank when the rad cap isnt sealing. similar issue as the system isnt pressurising correctly so any leaks/ splits will cause similar symptoms to a dodgy rad cap. I found one on the underside of the heater matrix to cylinder head pipe. it wasn't always open so would seal. when the engine moved it opened the split and caused the system to lose pressure and overheat. I only found that by chance as it was hissing at me today when I first tested it this morning. I sealed the hole with my thumb and the bubbling in the expansion bottle stopped. I didnt see any leaking water as it was dripping onto the head and evaporating we shall see if I'm right in the morning when I whip the other hoses off! Quote Link to comment Share on other sites More sharing options...
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