laidbackluke Posted January 11, 2014 Share Posted January 11, 2014 Evening all, right we have a quite a doosie for you guys. as you may all know buster and keyser being the heroes that they are very kindly fixed up my car and got me back on the road before Xmas. A few weeks ago however, one of the coolant hoses popped off (the small on located to the left of the plenum, tucked behind the larger one) it looked to be just because the clip wasn't quite secure, anyhoo, i popped it back on, topped up the water and away i went. Since this though the car has been overheating, the boys put it down to an air lock and bled the system only for the same thing to happen again...and again last Sunday the Zed Shed took a little road trip out to Dorchester to try and solve the problem, we took out the thermostat to find it was pretty worn, so to get me on the road again without overheating removed the thermostat. now is where it gets annoying.... After testing a spare thermostat to ensure it was working we fitted it back into the car. When ticking over its fine, nice and warm in the cabin and the temp gauge is sat normally. However after a few minutes of driving the cabin goes stone cold and the car overheats again. There's no symptoms whatsoever that point towards the head gasket, and Ive been driving it this week for a good few miles with no troubles, bubbles or signs of oil in the water. I hope this all makes sense! If anyone has any ideas at all please let me know and both Chris and Bob are verging on chinning me because we cant work out what it is. Quote Link to comment Share on other sites More sharing options...
Darren-B Posted January 11, 2014 Share Posted January 11, 2014 Bring the car to me & Octet @ the real zed shed & we will fix it for you 1 Quote Link to comment Share on other sites More sharing options...
Adrian@TORQEN Posted January 11, 2014 Share Posted January 11, 2014 TRUE story. Quote Link to comment Share on other sites More sharing options...
laidbackluke Posted January 11, 2014 Author Share Posted January 11, 2014 Bring the car to me & Octet @ the real zed shed & we will fix it for you ha thanks Darren or you boys come down and form a nissan superpower! a 350z mega power ranger if you will Quote Link to comment Share on other sites More sharing options...
Keyser Posted January 11, 2014 Share Posted January 11, 2014 Bring the car to me & Octet @ the real zed shed & we will fix it for you Your on - I'm lost at the moment - all the signs point at it being thermostat as when we take it out the car runs fine no overheating etc - when you put it in the lower hose is cold - so no circulation and the car overheats - had we not tested and used 2 thermostats I'd say it was that. So how long you need it for? just the day??? Quote Link to comment Share on other sites More sharing options...
Darren-B Posted January 11, 2014 Share Posted January 11, 2014 Water pump? Temp sensor? is the ecu reading water temp? whats the gauge showing? Are the fans working? Quote Link to comment Share on other sites More sharing options...
laidbackluke Posted January 11, 2014 Author Share Posted January 11, 2014 Im not sure about the sensor mate however id guess its pretty bang on as when its overheating you can hear the water boiling and steaming out the top of the expansion tank. as for the pump wouldn't that cause less pressure to build anyway, thus keeping the thermostat open allowing the water to flow? it really seems like once under load the thermostat decides to close as like Chris mentioned the lower pipe into the radiator goes stone cold Quote Link to comment Share on other sites More sharing options...
gareth29 Posted January 11, 2014 Share Posted January 11, 2014 (edited) I had a water pump fail on my vw - gave similar symptoms to yours The lack of circulation points to the pump? Edited January 11, 2014 by gareth29 Quote Link to comment Share on other sites More sharing options...
Adrian@TORQEN Posted January 11, 2014 Share Posted January 11, 2014 (edited) Are the fans spinning at all? Maybe they're slow before they're dying, a well know problem on the 350z, causing overheating. Edited January 11, 2014 by octet Quote Link to comment Share on other sites More sharing options...
laidbackluke Posted January 11, 2014 Author Share Posted January 11, 2014 Are the fans spinning at all? Maybe they're slow before they're dying, a well know problem on the 350z, causing overheating. Fans are spinning a treat matey....my knuckle can vouch for that 1 Quote Link to comment Share on other sites More sharing options...
laidbackluke Posted January 11, 2014 Author Share Posted January 11, 2014 I had a water pump fail on my vw - gave similar symptoms to yours The lack of circulation points to the pump? but why would it circulate when the thermostat is out? Quote Link to comment Share on other sites More sharing options...
Keyser Posted January 11, 2014 Share Posted January 11, 2014 Water pump? Temp sensor? is the ecu reading water temp? whats the gauge showing? Are the fans working? Well when it's not overheating the gauge shows normal When it is over heating and has steam coming out the expansion tank the gauge shows HOT Water Pump - works fine when the thermostat is removed so unlikely but we did consider it. Fans work perfectly Quote Link to comment Share on other sites More sharing options...
DavidS14 Posted January 11, 2014 Share Posted January 11, 2014 My only thought would be a worn or partially seized pump. Lower flow would mean that with the restriction of the thermostat the flow drops low enough to overheat but with no restriction the flow is high enough to keep the temps under control ? Quote Link to comment Share on other sites More sharing options...
Adrian@TORQEN Posted January 11, 2014 Share Posted January 11, 2014 Are the fans spinning at all? Maybe they're slow before they're dying, a well know problem on the 350z, causing overheating. Fans are spinning a treat matey....my knuckle can vouch for that Hmm, mine were doing the same thing, they looked like they were working, not seized, but they were slower that they should have been, you couldn't tell the difference just by looking at them. The minute I've changed them with brand new ones overheating was history Quote Link to comment Share on other sites More sharing options...
Neilp Posted January 11, 2014 Share Posted January 11, 2014 The fact that the cabin goes cold is weird as usually it heats up when theres an airlock when moving and goes cold when not moving. I still think theres an air lock though. Id drain fully and fill as stated with the manufacturers instructions which means you will be there for ages doing it. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted January 11, 2014 Share Posted January 11, 2014 I had similar when only one of my fans was working was fine at road speeds but overheated when at idle. The engine relies heavily on the the fans when at hot idle, or in slow traffic. Quote Link to comment Share on other sites More sharing options...
mace Posted January 11, 2014 Share Posted January 11, 2014 Had this on a supra the once (dont know about the 350z) turned out to be the Rad cap (not the expansion tank cap) does exactly what your describing when it goes. Quote Link to comment Share on other sites More sharing options...
buster Posted January 11, 2014 Share Posted January 11, 2014 I mention the rad cap today. Quote Link to comment Share on other sites More sharing options...
buster Posted January 11, 2014 Share Posted January 11, 2014 just found a spare in the garage...will try it next. 1 Quote Link to comment Share on other sites More sharing options...
Darren-B Posted January 11, 2014 Share Posted January 11, 2014 (edited) Good point Mace Do the pipes pressurise as the temp goes up. If the system doesn't hold pressure 1.1bar I think the standard cap is, then this will affect the efficiency of the cooling system. But if the pump & thermo stat are good & all the hoses reconnected (in the right places) I'd be looking at an airlock. The 350z can be a right bugger to fill without getting an airlock. Edited January 11, 2014 by Darren-B Quote Link to comment Share on other sites More sharing options...
a2orry Posted January 11, 2014 Share Posted January 11, 2014 If i had that problem I would be thinking the water pump as it will pump water through the larger radiator hoses with the thermostat removed but put the thermostat back it can't pump water through the smaller hose to the heater matrix may be the impeller is loose on the shaft. Quote Link to comment Share on other sites More sharing options...
GT4 Zed Posted January 11, 2014 Share Posted January 11, 2014 My guess too Dazza that's as it looks like everything is kosher its an airlock. It can be painful to get rid but I've devised a few techniques and get it right 1st time now. Fill up slowly with coolant with the posterior bleed nipple open. When it appears full keep squeezing the pipes sequentially to get some more air out and keep topping up until rad full and replace cap. Final trick is to raise the rear of the car to make he posterior nipple the highest point on the system. Fill now will funnel slowly through the nipple while still squeezing pipes intermittently until full. Close nipple Now start the car and up to temp and put on heating to circulate coolant and more air. While this is happening intermittently bleed the nipple until no more air. Level out the car and open rad to too up if necessary. Go for a good spin and repeat the process. Should be job done. I replace coolant yearly and also use the 2.3bar car to pressurize the system more. Quote Link to comment Share on other sites More sharing options...
buster Posted January 11, 2014 Share Posted January 11, 2014 I was always told it was the front of the car that needed to be jacked ? will give this route ago. Quote Link to comment Share on other sites More sharing options...
GT4 Zed Posted January 12, 2014 Share Posted January 12, 2014 Air rises to the highest point which is the posterior bleed nipple. By jacking the rear you are accentuating this but also helping the air trapped within the engine block to escape towards the top most part rather than go below before rising to the top and burp out through the rad👀 Quote Link to comment Share on other sites More sharing options...
Darren-B Posted January 12, 2014 Share Posted January 12, 2014 I don't think jacking the back up is going to make much difference, when y0u fill the system you are always going to get a some air in the system, so long as you have the heater set to hot & fill the system slowly you should eliminate most of it. The rest of it should find it's own way out through the expansion tank. As the temp rises the air in the system will rise in pressure & ill be released into the expansion tank & when the system cools water/coolant will be sucked back in 1 Quote Link to comment Share on other sites More sharing options...
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