by Ian Linden » Tue Nov 27, 2018 10:27
Hi George,
This is a new one on me. The manual is reticent about the function of the "engine cooling water pipes" to the throttle body.
I can think of two possible functions:
Vitara throttle bodies have a thermowax valve which closes when the coolant is hot, and is open when it is cold. The function is to supply extra air to a cold engine to supplement the IAC valve, as that valve lacks the ability to control over the full temperature range. It is well documented in the Vitara manual, so unlikely to be relevant to the Cappo. However, as you say there is a valve in there, maybe that's it? Clearly, it would need to flow water continually to work, so if this is what it is, it must be blocked.
The other is to prevent throttle tract icing in very cold, damp weather, by circulating hot water through passages inside the casing, in which case the valve may only open when very cold temperatures are experienced, because heating the throttle body when not required would reduce the volumetric efficiency of the engine (like dispensing with the intercooler).
My thoughts are that, if it is the first function, but the engine starts and idles well, don't worry about it - perhaps it was fitted but disabled during engine development (but why retain the pipes?). If it's the second, you could try blowing very cold air through the throttle body to see if it opens.
Anyone else any ideas?
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