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How to check engine vacuum hoses
Check each hose for bulges and swelling.
If a hose feels soft or spongy when you touch it, this can indicate damage caused by your car's oil.
A swollen hose that is cracked and hard is often caused by heat damage.

Choose your answer from: a). It could also be caused by a leaking coolant system. A damaged hose that smells like gas or oil can indicate strain on the engine or air supply.. b). Inspect each hose for bulges, in particular for the burr mark. To check a hose for tarmering, insert a clean measuring tape onto the hose.. c). If your hose feels firm to the touch, you have recently recently replaced a faulty hose. A solid, sturdy hose will be hard to bend.. d). These hoses can be too close to heat sources under the hood or it may be the result of overheating. Bulging hoses can also be caused by electrochemical degradation when there's a coolant leak dripping onto hoses..
Answer:
d).