Thread: How to - wash the engine bay ?

I am also interested in this as I was contemplating the very muddy interior of mine last weekend.

I haven't done it yet as I have heard a number of horror stories about it. From memory wetting the ?ECUs behind the battery compartment is a big no no. All looks to be quite a bit of other exposed Stuff.

I was going to use my pressure washer on a very fine mist and stay away from the back of the Bay and fuse box and battery boxes but I chickened out and feebly wiped a few surfaces with a wet rag.

I've washed mine a couple of times recently. Generally a good spray with degreaser in the dirty areas and then hose out from above. I don't squirt a lot of water in / near the "electrical / computer" areas, but these are usually not dirty anyway.

Haven't had any problems so far. But I do not use the pressure washer / gerni gun under the bonnet. Don't really use it on the body / paintwork either. That is reserved for wheels / wheel arches and underbody when needed.

I use a cheap cleaning gun. You can adjust the spray pattern, the air pressure .You can use water ,kero ,degreaser or whatever you think is appropriate . Good for those "hard to get to" spots. Btw, I only use it on Series vehicles. That's all I've got. .W.

Originally Posted by AnD3rew

I am also interested in this as I was contemplating the very muddy interior of mine last weekend.

I haven't done it yet as I have heard a number of horror stories about it. From memory wetting the ?ECUs behind the battery compartment is a big no no. All looks to be quite a bit of other exposed Stuff.

I was going to use my pressure washer on a very fine mist and stay away from the back of the Bay and fuse box and battery boxes but I chickened out and feebly wiped a few surfaces with a wet rag.

I think that's about it or you will have issues?.

Never been game to put the hose anywhere near the engine bay in mine.

I've washed mine a few times without issue. Spray of 'truck wash' CT 18 or what ever it is. Let it sit as directed. Hose off (I've not used a pressure washer as I don't have one) being mind full not to wet the electrical 'stuff' behind the battery box. The whole lot comes up a treat.

There are however numerous examples on here where washing the engine bay has cause significant issues.

Ive heard Kero and dishwashing liquid mixed up and spray in there apparently.

In my youthful years, I was a car detailer. I detailed cars/trucks/buses/boats and even some light aircraft. I detailed for almost 20 yrs.
Any commercially available degreaser will be fine to use.
Just read the directions on the bottle/can.
Never degrease an engine that is hot! Never! Degreasers will etch themselves into a hot surface, and the temp difference between your cold tap, whether pressured or from the tap (low pressure) will cause some issues.
After spraying engine bay with your chosen poison, give a light scrub (or agitation) then let sit for a min or two.
Then all that is needed is a subtle direct hit from your chosen hosing method.
I've seen sooooo many people that think the pressure washer is supposed to strip everything and make it all shiny. Its not a magic wand. Gently gently is the aim of the game. Its a bit like paint prep, more time preparing less errors afterward.
Obviously don't spray ecu or dizzy directly. And don't spray the sound deadening mat under the bonnet. That never ends well.......

Hi There,
I washed under my engine bay a few years ago and managed to get water on the tranny module behind the battery on the R/H side of the engine bay looking from the front. That was a very steep learning curve, easily diagnosed thanks to Sniegys help, easy to fix and highlighted a bit of a design issue.

Personally I used a product called "Simple Green", as mentioned above, cold engine, low pressure spray, I do remove the engine cover to get better access, I then use the hose nozzle on "sprinkle", low pressure. I then spray a bit of WD 40 around the electrical connections I can see to make me feel better about soaking the engine being careful not to get any on the serpentine belt or pulleys.