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Coolant Probs & Melt-Downs

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Have owned an 2004 Avensis D4D T3S Tourer for about 18 months. It had 130K on it then but now has150K. Owning this car has not been all pure unalloyed joy, especially with it's penchant for shedding stupidly flimsy plastic bits & bobs........the wafer thin engine undercover & it's puny clips just couldn't stand the armies of speed bumps in our area so it got binned within 3 months. It's needed more repair & maintenance than I'd hoped but I've put that down to it's age & the realization that a decent service history don't necessary confer any guarantees if the guys doing the inspection & repair can't be trusted. While it was recently in for a recall inspection at our local Toyota garage I asked them to investigate some odd & very loud ratling noises coming from under the bonnet & they diagnosed a buggered Dual Mass Flywheel. By the time I'd driven home & changed my underpants my own puny brain had begun to kick in &, 5 days later I'd tracked down & had fitted a cheap non-OEM Air-Con pump. That cured the "buggered DMF" for a fraction of what Toyota quoted. What a bunch of incompetent sharks.

On balance though, I must say that the car has been efficient, reliable & megga-economical on deisel, if a tad uninspiring to drive.

The real mystery though......... & this is why I write........ the big problem..... is this.

One hot day this summer, my wife said she could smell something burning so I pulled over into a lay-bye, turned off the engine & lifted the bonnet. There WAS a faint haze of something coming from the FNS of the engine bay, but nothing hectic & no other signs. I thought I'd spark the motor up to see what's what but it just lazily & slowly turned for 3 seconds & then wouldn't turn any more. The mystery ended with the AA man I called out, after a good hour of multiple testing & brain searching, telling me I'd had a very lucky escape. A partial seizure. I'd lost almost all of the coolant via a tiny leak on the rad, which had grown a little Oak Gall type growth the size of a peanut showing where the leak was. Fore some strange reason the dashboard temp gauge had never registered anything other than normal &, even stranger, Toyota felt there was no need to equip the car with a low coolant warning light or alarm. The very good AA man bunged some Rad-Weld type stuff in &, giving the engine a very thorough diagnostic health check, eventually pronounced the patient well again. A credit, he said, to the Toyota design & build exemplified by this particularly excellent engine.

I had every intention of following his recommendation to replace the rad but, when I got a quote, those underpants needed checking again. I instead carried water & checked & checked & checked, but it never lost a single drop. I recently had a fairly major service at my local preferred garage (when they did the Air-Con Compressor) &, having told them about the coolant loss & near seize-up in summer, they ran a pressure test on the coolant system & also ensured the coolant concentration level was correct.

Two weeks later, on Christmas & New Year Hols, 300 miles from home in the Lake District, after a couple of 1 mile journeys from cold in the space of two hours then, driving up-hill on the third journey, the car lost power & began discharging thick black smoke from the exhaust. I immediately coasted downhill in reverse, engine on tick-over, until I could turn & then coast back to our holiday place. I revved it up & everything seemed normal..... & no black smoke. I lifted the bonnet & realized there was no heat from the the rad. Rad, hoses various tubes......... all stone cold. Temp gauge showing normal, warmed-up, working temperature. Couldn't see the expansion tank level (it's virtually impossible to see unless you have perfect lighting) so assumed it was low & left it for an hour for the engine to cool off. I later came out with a full bucket to find that the level was normal.

So................... WHAT THE HELL IS GOING ON?????????????

I'm thinking it's possibly an erratic Thermostat staying jammed shut. Maybe it's been the problem all along.

If only the solution were as simple as a new thermostat....... but if it is, I'm sure it'll need extensive dismantling to access it.

An ideas?


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I would go for the new thermostat and have the rad checked aghain. Also refurbed rads are a lot cheaper than buying new.

Also what is your coolant like? red or brown? if its brown then get its checked out

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It's quite an easy job really if you are good with tools, I have attached a diagram that tells you how to do it on your car.

Just click on the diagram to enlarge it.



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