In another thread, I read that Nuts, that's exactly the kind of tool I wanted to use. Where can I learn more about this? Is the damage risk described somewhere? Does this also apply to the NHW11, or is it NHW20-specific (like the thermos)? Does anybody have positive or negative experience using the vacuum-type refill tools? Thanks, -Chap
Some additional information on how a commercial garage says they do this change/bleed process can be found at: Art's Automotive - 30K Service, 2nd Generation Prius Scroll down to the pictures of the coolant swap. I'm making the assumption that you are talking about inverter coolant. Hope this information is useful.
the system operates under low pressure. the manual for the tool (at least the ones DH has seen) specifically state that you DO NOT use the tool on low pressure systems. he has never once used it on a prius despite the time saving features and the sheer number he's done and the fact that the job doesn't pay too great for the time needed... because he never wanted to piss off a customer. another shop has put their insurance policy on the line to do it... more power to 'em. DH wasn't about to be the first to do that.
Low pressure systems = thin walls (and probably weaker seals/gasketing.) Pull too much vacuum and something will likely crush like a coke can. And too much doesn't have to be much at all if a system is not rated for more than a few inches of vacuum. I've seen these sort of mistakes made in industrial vessels and it is not pretty. On process equipment design when faced with moderate operating pressures on modest sized tanks/towers/other vessels we would specify full vacuum ratings as well without adding to the cost (essentially just changing the tag/documentation.) This was because for moderate pressure systems satisfying the internal pressure spec required thick enough walls that the vessel could withstand full vacuum as well. Adding the vacuum spec simplified vent/relief systems, maintenance, etc.
Aha. I trust that's the inverter loop, and the ICE loop runs at the usual 13 psi or so? Then perhaps only the inverter loop is a concern? So the source of the concern is the tool warning (don't use me on low pressure systems) combined with general knowledge that the inverter loop is low pressure? Or has Toyota issued anything explicit recommending or unrecommending the technique? Thanks, -Chap
you'll have to check the manual for the tool you have to see what psi is ok. it's your car, you make the call. it's not like DH's situation where he was working on someone else's car and was relying on that customer's absolute satisfaction to bring him continued business. (and not screwing up someone's car to the tune of $xxxx, possibly costing him his job.) inverter coolant runs at 2-6 psi, engine at 10-14. DH never used the tool on a prius, period. he had an informal discussion with his regional training instructor, who recommended against it.
Hi Chap, It turns out that the 2G inverter coolant loop is easier to purge out air compared to Classic without resorting to artificial means like the vacuum tool. However Classic can be done without using a tool, just plan to spend lots of time. The 2G engine coolant change is much more difficult for a DIYer (without benefit of the Toyota hand held tester or PC) compared to Classic because of the presence of the coolant heat recovery canister. However, with suitable persistence it can be done successfully.
i ran across DH's matco vacuum refill tool manual today. reminded me of this thread. here's what the warning states:
