What parts to cover before an engine bay clean?

[Chippps]

Hey guys, 

I'm about to replace my distributor o-ring and rocker cover gasket. 

Going to have to do a degrease and hose off of the engine bay. 

Can anyone help to make sure im covering the right components with plastic before hosing the engine bay? 

[Tony Prodigy]

Hi Chippps. Modern engine electricals have plug seals in them so water ingress into these is not an issue like the old cars were. Just try not to be too vigorous around electricals. They will withstand a degree of washing and pressure washing if you have too. I have pressure cleaned many engine bays and the only thing I would really cover is the alternator and the spark plug leads on the top of the engine. Just place a plastic bag over  the alternator so no chemicals or water can enter the windings inside the openings. For the spark plug leads, just check to make sure they are forming a seal on the square bits, otherwise put a bit of vaseline around the edges to help seal them against the metal. That's pretty much it. If you happen to get water in the spark plug wells, just blow the water out with compressed air or something similar, or push a dry cloth down in there to soak up the water..

Spray the degreaser and agitate with a stiff bristle brush (paint brush will be fine) to help loosen the grease/oil reside and then wash, preferably with a high pressure cleaner if you have one. Repeat the process for better results. After A degrease you can wash with car washing soap as degreaser will leave an ugly, dry residue. I also recommend a spraying of Aerospace 303, once it's all dry, to nourish and keep all the plastics and rubber conditioned. Degreaser is good for what it suggests but can be harsh on softer components.

Any rubber treatment will be ok, but Aerospace 303 is the best stuff for this.

Edited April 11, 2021 by Tony Prodigy

[Chippps]

You're an absolute legend... Thanks mate 

[campbeam]

I knew that Tony would be able to provide an excellent answer speaking from his own experience.

Good idea to take care and preferably avoid the fuse box and any ECUs. 

I have not yet done this but I have noted a few YouTube videos where they have used Tyre Foam as an engine bay cleaner. Just mentioning this as a consideration for your next engine bay clean.  

[Tony Prodigy]

11 hours ago, campbeam said:

Good idea to take care and preferably avoid the fuse box and any ECUs.

Yes and understandably so. The connectors on the ECUs are well formed and have an excellent seal otherwise the factory wouldn't have them in a hostile environment such as the engine bay. Fuse boxes are well shielded too, so don't worry too much about that either. Incidental cleaning/pressure washing won't hurt anything unless you are deliberately trying to force the issue.

With the O.P.'s engine, being older and having the spark plug leads instead of coil packs, those leads tend to shrink around where they seal on the top and you can get moisture enter the plug wells, which makes me extra cautious. It's not a big issue, but it will have you spending time correcting it if it does occur. If the square bits are such that you can wriggle them too much, I pop them out even and stuff a cloth into each hole and then wrap the ends of the leads in plastic.

I didn't go into too much detail in relation to products and detailing method, as I suspect Chippps probably doesn't have the range of products as others would. Degreaser is one of many products I'd use, but for simplicity, his approach will be adequate all things considered. Perhaps after this Chippps may get the detailing bug as I did many, many years ago 🤪

[Tony Prodigy]

12 hours ago, Chippps said:

You're an absolute legend... Thanks mate 

You're welcome buddy. Happy to help 

[Tony Prodigy]

4 hours ago, Raviolly said:

I would just use low water pressure and cover the air filter and the fuse box before starting.

Modern cars are pretty well built, especially now that they are full of electronics, so the car makers ensure that most, if not all the components in the engine bay, can withstand the elements otherwise they can go bad very quickly and cost too much to rectify.

Air boxes have excellent seals so water is practically impossible to leak in, even when washed with a high pressure machine. When I say High pressure, it's just a generic term I use for the equipment as you don't go right up to the engine bay up close and blast it into eternity. Keep a healthy enough distance from solid components and vary the lance distance on the more sensitive items like the electrical connections and smaller vacuum lines. Try not to focus to long on any one spot. Keep the lance moving in such a way that you don't force the water around. More like sweeping, if that makes sense. The air pressure generated by the water pressure is enough to rinse everything off.

I always cover the alternator as I don't want anything "wet" entering the vented sections where the windings are, especially when using chemical cleaners. I know the internal windings are lacquered and can withstand moisture/water, but it's not good practice to wet the alternator. It will last much longer if you cover it. The chemical leaching can degrade it quickly.