What the word engine bay has to mean before anybody times anything
Half of the arguments about bay time are arguments about the boundary. One shop means the top of the engine and nothing else; another means the whole compartment including the inner wings, the radiator face, the strut towers, the plastic covers and the underside of the bonnet. Write the list of surfaces down first, one line each, in the order a technician will actually reach them. Until that list exists, a time estimate is a guess about an undefined job. The same list is also what tells you whether you are talking about a work-lot of three vans or one classic car, because the surface list of a modern engine bay and that of an old one with a cloth-wrapped loom are not the same document.
Then record the reachability of each line on that list: reachable with a hand over the front, reachable only by leaning across, or reachable only after something has been undone. Reachability, not area, is what eats the minutes in a compartment, and it is the column people leave out of their estimates.
Sort the deposits, because the deposit sets the time
Two bays that look identical from the front can sit for completely different lengths. Name the soil on each surface line rather than describing the bay as a whole. Loose road grit sitting in a plastic cover. A soft oil film that came off a leaking seal and has not been there long. Thick, dark, tacky sludge where oil has been boiling on a hot component for months. Grease packed with dust on the fan shroud and around bolts. A white salty bloom on an alloy bracket or an exhaust shield. Old wax or dressing that has been applied repeatedly and now holds dirt like glue. A dried coolant paste in a seam. Each of those behaves differently under heat and dwell, and a time plan written without them will be wrong in both directions.
A practical way to handle this is three deposit grades on the sheet, with a note beside each surface line saying which grade it is on the average bay of that type. Grade one comes off with one pass. Grade two needs dwell time, which is waiting, not labour, but it still occupies the bay and therefore still costs you a slot. Grade three may need a second working cycle after the first has been inspected, and any honest estimate has to carry the possibility of that second cycle rather than assume the first one finished the job.
Draw the line where nothing may get wet, and count it as time
Every minute spent deciding this on the fly is a minute that never appears on the invoice, and it is also where mistakes are made. Set the exclusion boundary in writing before the first bay of the week: the alternator and starter bodies, the ignition coils and their plugs, the fuse and relay box, the engine control unit and its connectors, the air-intake opening with the filter out, the battery terminals and the battery itself, the brake-fluid reservoir and its cap, the dipstick and oil-filler openings once the caps are off, the labels and VIN plates, and any connector that is cracked or missing a seal. Beside each item put the alternative that is being agreed instead, which is usually a covered wrap, taped sheeting, a bag held with a rubber band, or a wiped-clean-by-hand instruction. Some bays also carry parts that were replaced recently with parts that are not sealed properly, and that only becomes visible when somebody looks with the boundary in mind.
Now time the shielding itself. On a dusty bay that has not been cleaned for a while, covering and uncovering can cost as much as the cleaning, and if it is not written into the estimate the whole plan looks achievable when it is not. This is the single most under-estimated block in engine-bay work.
Break the job into the blocks that actually consume time
Do not estimate one number for the job. Estimate six, and add them. First, access and preparation: bonnet or hood open, cool enough to work on, the vehicle positioned so the operator is not standing in a corner with their back to the light, any wheel arch or inner wing that has to be reached with a torch. Second, shielding and isolation, timed for each vehicle rather than assumed. Third, the working pass itself: how many passes one panel needs, and how long each pass takes in a corner you cannot get a hand behind. Fourth, dwell waiting where the soil is graded two or three. Fifth, drying and re-check, which is the block everyone forgets: a bay that looks clean and is still wet will look dirty again within an hour, and damp around connectors is not something to leave for tomorrow. Sixth, restore and hand over: covers back, wrapping gathered and binned, the engine started by the person who owns the vehicle, and a note of anything that looked wrong while the bay was exposed.
Add a seventh block if your site needs it: where the run-off goes. A bay that has been washed down has to drain somewhere, and if the operator has to move the vehicle, lay down an absorbent mat, or wait for a gully to clear, that is time you own, not time the machine owns.
Decide dry or wet per surface, not per job
The fixed unit in this manufacturer's range is listed as switching between dry and wet steam, and that switch is the biggest single lever on bay time, because it changes how much liquid ends up standing in the compartment at the end of the pass. A drier working condition lifts soil and puts very little water down, so drying and re-check shrink. A wetter condition does the heavy lifting on baked-on sludge in far fewer passes, but everything around it then needs the drying block, and the exclusion boundary has to be tighter. The mistake is choosing one for the whole bay. A sensible plan says: the wetter condition on the bonnet underside, on the inner wings, and on the block wherever soil has been baking; the drier condition everywhere a connector, a label or a bracket lives.
That decision belongs on the surface sheet next to the deposit grade, so it is made once and then repeated, rather than being improvised by whoever happens to hold the wand on Thursday. Recording it is also what lets you compare one week's times with another week's, because you can see whether the difference was the deposit or the setting.
Choose a work-lot, because a per-bay number means nothing without one
The first bay of any session takes longer than the ninth, and the difference is not the machine. The operator is re-finding the torch, re-deciding the shielding, re-reading the layout, and waiting for the water and power arrangement to catch up. So never quote from a single bay. Pick a work-lot that matches how you actually work: one vehicle, then a batch of five of the same type. The first bay is setup, the second is the real first result, and the last two of the batch give you a figure you can put in a plan. If the lot is a mixed fleet, run one lot per family, because a van with a plastic-covered engine and a pickup with the block exposed are two different jobs wearing the same name.
The unit of work matters just as much. One bay, per vehicle, per visit, with a defined surface list, is a workable unit. Anything larger and you are averaging jobs that should not be averaged.
Measure on the floor with a stop condition written first
Set the acceptance condition before the trial starts, in terms a person can look at and judge: the plastic covers free of the black film, no oil visible on the horizontal faces, no sludge in the seams under the manifold, no white bloom on the brackets, all connectors and labels dry and legible, nothing standing in the bay at the end. Photograph two of the worst patches before the first pass and photograph the same two patches after. Then write a stop condition, because a trial that can run forever produces no number: end the trial if work is interrupted twice for re-covering, if a connector has to be blown dry before the vehicle will start, or if the same patch has had three passes and is still holding soil.
Keep one line per bay with who did it and who checked it, and keep the checker separate from the person who cleaned it. A trial where the operator grades their own work gives you a pleasant number, not a usable one.
What the machine itself changes about the number
Where the power comes from changes the plan. A machine that runs on its own battery and water supply can follow a vehicle around a yard; a machine that has to be plugged in and plumbed in can only work where the outlet is, so the yard layout starts dictating the estimate instead of the bay. A fixed installation that stays in one place suits a line of bays handled at a single position and suits a business where the vehicles come to the bay; a machine on wheels suits a site where the bays come to the vehicle. Decide which one you are planning for before you compare any times, because a comparison between a fixed position and a mobile unit is usually a comparison between two different working methods.
Two more things belong in the estimate, not in the specification. The holding volume of a tank is a storage figure, not a figure for how long you can spray before the operator walks away, and the walk is real time. And the accessory set delivered with the machine determines what the operator can reach without a second trip; a brush for a plastic cover, a narrow nozzle for a seam and an extension for a strut tower are all things that either save the minutes or cost the minutes.
When a machine is being quoted to you, ask for the published rows in writing for that exact unit rather than reading them off a page, because the rows are not written the same way from one page to the next, and a comparison built on mismatched rows is not a comparison. Fixed Steam Cleaning Machine PowerDe HW02 is one such page; read what it actually describes alongside the rows, since the applications printed there belong to that unit and do not transfer to a line, a yard or a workshop that was never part of the design.
Turn two measured runs into a standard one page long
Once the lot has been timed twice, write the standard while it is still obvious. One page per family of vehicle: the surface list in order, the deposit grade beside each line, the working condition for that line, the exclusion items and their covers, the time blocks with the measured figure for each, and the sign-off condition at the end. Keep it on paper in the bay, not in a folder on a shelf, and have the first three bays after the standard is issued timed against it rather than assumed to follow it. That is how a standard survives the arrival of a new technician, which is the point of having one.
Put a review date on the page. Deposit mix changes with the season, fleets change, and a standard nobody re-timed has usually drifted from the floor without anybody noticing.
What a time estimate does not settle
A defensible number tells you how long the task takes. It does not tell you whether the task is allowed at your site, what may be discharged where you work, or whether the way you are working satisfies your own safety rules; those sit with the site, and they have to be answered before the first wet pass, not after. Nor does a measured figure for one workshop transfer to another workshop with different lighting, different reachability and a different soil mix. If the machinery side of your operation ever needs a written figure, a documented process or an accessory set that has been tested rather than assumed, that is a conversation to have with the supplier rather than a number to invent: customized steam cleaning equipment is where that starts, and steam cleaning equipment testing is what stands behind a claim that it was tried on something rather than assumed.
