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Curtis, Australia Car Mechanic
Category: Australia Car
Satisfied Customers: 1609
Experience:  Qualified Automotive Mechanic, LPG & Airconditioning Diagnostic Technician.
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Ken. VT Commodore. Has had new radiator, 2 x thermostats,

Customer Question

Hi Ken. VT Commodore. Has had new radiator, 2 x thermostats, hoses, radiator cap. Uses about half a litre over 2 days with short trips (to the shops and back).
Temp gauge sits just below half normally. Stop at lights, idle, engine runs rough for a moment and the fans kick in and the temp gauge starts to rise eventually 'hot' warning. Pull away with engine up to 2k rpm and gauge starts to drop back to normal. Weird!
Any ideas?
Submitted: 2 years ago.
Category: Australia Car
Expert:  Gary replied 2 years ago.
Hi there,I say your next step is if there no apparent external loss, I would pull the intake manifold.Sounds like water loss from the coolant passages into an adjacent intake port, once cooling system pressure builds up.Was the cooling system bled correctly after each repair?Gary
Customer: replied 2 years ago.
Well the major work was done by my mechanic so I assume he did but this problem occured after that and he suggested I keep an eye on the coolant levels. I then replaced the thermostat myself but didn't do any bleeding. How is that done?
Expert:  Gary replied 2 years ago.
Hi Ben,There is a bleed nipple in the top of the thermostat housing.You then need a radiator filler bleeder which is a device to allow a higher level of coolant than the engine to allow the airlock to bleed out.You can make a device like this out of a plastic bottle with a neck that seals well in the radiator neck.Cut the bottom of the bottle off, fit the neck within the neck of the radiator, clamp off the overflow hose.Fill the bottle which is now higher than the radiator, undo the bleed screw in the thermostat housing.Wait until coolant flows, shut the screw, start the engine heater on, Fan speed 1, let the engine warm a little, crack the bleed screw to allow more air out until just coolant comes out, lock the screw, keep the bottle high in level, when your happy the coolant has no air, turn the A/C which cool the radiator and the level will drop. Allow the engine to take in as much as it will, take the bottle off, fit your cap, shut engine down, check level in overflow, top up a fraction high. Allow engine to cool right down, check level in overflow, if ok, go for little drive, come home, check level in overflow, hot and cold. Radiator cap should be hot to touch, telling you the coolant is right under the cap.While engine is hot, hoses should be firm/hard - as in no air.Gary
Customer: replied 2 years ago.
Thanks Gary - I'll do that tomorrow and let you know what happens.Cheers
Expert:  Gary replied 2 years ago.
Hi Ben,How did you go with the bleeding procedure?Did it help at all?Rough running still?Gary
Customer: replied 2 years ago.
Hi Gary,I did the bleeding procedure ok but haven't driven it far enough to tell if the problem's solved or not. It used to take 2 days after topping up the radiator before the problem showed up. I'll take a trailer load of garden cuttings to the tip tomorrow and give it a good run around town and see how it goes.Cheers
Expert:  Gary replied 2 years ago.
Hi Ben,That's a good sign.Hope all goes well.Gary
Customer: replied 2 years ago.
Hi Gary - I travelled from Canberra to Kiama and back last weekend and the temperature gauge stayed normal. It didn't budge even going up Jambaroo pass which puts a fair load on any engine. After that, I topped up the radiator - it needed a large glassful, not much at all. The only time it plays up is at idle, like waiting at the lights, and doesn't always do that. The engine 'shudders' a little, the revs increase slightly, the fans come on (sometimes) and the temperature gauge starts to rise.I'm still not confident that it's fixed.
Expert:  Gary replied 2 years ago.
Hi Ben,As a Holden tech for many years, I'll tell you that if the thermostat has been overheated, then they do become unreliable.It still like you have a weep somewhere, quite possibly within the engine.I would inspect the spark plugs, you have to know how to read a spark plug for coolant contamination etc.If you're really keen, I add a flushing agent to the existing coolant for a short period, drain and flush that out, add new coolant with a water pump seal lubricant pellet set (comes in a bag of 3 from Holden, not expensive) and perform a good bleeding procedure, then monitor coolant level, temp gauge operation.I would also check for any vacuum leaks, they are prone to purge hose failure from the solenoid to the throttle body.Spark plug gaps are critical to keep in check, the leads are prone to crossfire, and the coil packs then work harder and then ultimately fail.Hope this helps.Gary