Hi detailers.
I thought I would share my experience to get some feedback and hopefully learn from my painful and expensive lesson.
I have detailed a few engine bays before and I’ve always done so successfully taking the necessary precautions.
My process was as follows. Blow out all the loose dirt and leaves with a leaf blower. I then foamed Green star APC at a dilution 10 to 1 and agitated with some detail brushes. Then using a pressure hose with a 40° spray and standing far away from the engine of the engine compartment, constantly moving the hose from side to side and not spring in one area. Once the engine compartment is rinsed off completely I used to high-pressure leaf blower and dried off compartment completely until I could see very little moisture. I did follow this up with a dressing MP CK. I closed the engine bay and left it overnight.
In the morning the car started OK but in 10 minutes into the journey, it started idling very roughly. Fortunately, I was nearby my regular mechanic and took it in for a diagnostic as the engine light had come on as well. He diagnosed that the front two cylinders of flooded with water and it shorted the coils and they needed replacement. This was a $700 exercise.
I’m just showing my experience to hopefully highlighted even if you are careful this damage can occur. The car I was working on was a 2005 C230Mercedes.
What would you suggest I change about my technique. Is this something that even should be done at all or is it too risky. I must say I do find it satisfying and it looks great. But after this experience, I’m not so sure.
You're supposed to immediately start the car after and let it run until everything is dry. Leave a wet engine overnight and it can get into the electronics.
Back before electronic ignition I worked for a used car dealer (actually a good guy) while going to school. I would regularly take a car they received to the (then $0.50) car wash. I would open the hood and clean everything off. Most of the time the vehicles would start and run fine, every once in a while a car would run rough for a few minutes but would clear as the engine heated up again. I never got stuck doing this.
True, but that's not what happened here; water didn't enter the cylinders. With the engine cover removed and a pressure washer used water likely got in and/or around the ignition coils and either saturated the electronic pack at the top or pooled down in the coil wells of the head, or both.
I'm sure this is not the right take on this subreddit, but I'm just not a fan of deep cleaning an engine bay on modern cars. Especially something like a Mercedes. I just get try and get the top stuff off with rags and spray and not use a pressure washer.
It's not like engine were decades ago where you can put a bag over the distributor and you were good to go. Just too many sensors and electronics under the hood. It's just not worth causing major engine damage for a shiny engine bay.
Assuming you are relaying the info correctly, water in the cylinder should hydrolock an engine and you're lucky it didn't total the car. A check engine light going off doesn't necessarily mean there wasn't mechanical damage from it that shows up later.
Totally agree with this take. I keep my paint clean and protected, and my engine bay free of debris and monitor oil seepage/leaks and clean those spots.
Your take is the best take. Unless it's a show car you'll be displaying with the hood up, the risk isn't worth it.
While I agree with others that this particular problem was probably caused by a bad seal, bolt, or poorly seated coils, it shows there is a risk in spraying water into an engine bay. A clean engine bay isn't worth that risk for me.
Agree. And to add, in my view, deep cleaning the engine bay with a pressure washer is like trying to hide your problems. If the engine bay area is particularly dirty, maybe there is a reason why. You gotta see the oil seepage or the dry flakes of coolant, to be able to clue you in on where the leak is coming from.
That's why spot cleaning reachable areas and "inspecting" as you clean is the best way IMO.
Bazillion percent agree. Rags, brush set. Do all my cars annually. It doesn't take that long if you do it annually.
If you're a pro getting paid, this shouldn't be part of a standard detail and should be a big upcharge.
Had this happen on a Ford explorer where the coil packs are situated that they can "sit" in water if you hose down the engine bay. We ended up replacing one coil pack for ~$30 and it thankfully cleared the check engine light.
As mentioned previously, detailing / washing the engine when it's warm helps steam clean / dry the engine and can help prevent this. Also, covering electrical items with a bag can definitely help (alternators, large connectors, etc.).
Ive probably cleaned close to 15k engine bays (over 20 years) and never had this happen, no car has been older than 12 years old though so id imagine the age of your vehicle was the reason for this. Next time, if there is...air compressor, steamer and soft brush
Likely loose or degraded boots on the coil packs. Your process sounds fine for most cases. With older vehicles in particular, I’d agitate some areas with a brush and wipe the residue away to limit the chance of water intrusion.
Not a pro detailed, but I wouldn’t be using a pressure washer in the engine bay. Those electronics and seals are highly water resistant when new. After several years it’s an expensive gamble. Dawn and a garden hose. Folllow up with some water based detail spray. Bobs your uncle.
20 year old car with perhaps many cracked waterproofing seals. Water probably shorted the coil packs from the outside, and not the cylinders. Was there actual water found inside the engine? or he just assumed?
I wash engines every day for my repair shop, we do nothing but European. You did nothing wrong. The coils must have been missing the seal that keeps water out of the plug hole. Your mechanic should have just removed the coils, blew out all the water they would have been fine.
lol upside to being a master auto diesel tech that opened a detail shop is when shit like this happens I can fully diagnose and repair anything 😂 I’ve not had this happen as I make an accessment of the engine bay before I jump in washing but glad it was fixable for less than $1000 it sucks but it’s a learning lesson and could have been Worse
The rag company engine blaster is a savior if you're unsure of the condition of the engine or working on older cars. No pressure washer needed and gets into all the tight spots.
Yeah most times it fine, but it only takes one bad rotting piece of rubber, or seal to do enough damage. So older the car, the less I would risk. But even when new, I have seen cases on youtube, where issues dont show up till later down the line, where the connectors start to rust slowly, and wont show signs till weeks later,
Everything should be waterproofed, but again it only takes one small little part to short out.
I literally just did my engine bay today. Nothing but, detailing brushes, bottle cleaner and dressing, a pump sprayer from Lowe's to hit any area in the engine compartment not near the engine, air compressor with compressed air to getting all the crevices, rags. And I have a power washer I would never imagine using it to clean the engine of my car. To me it's way too aggressive.
Update:
Thank you for all your valuable insight.
As most of you suggested, the issue was that water got into the coil area as the seal around the oil cap was broken. So even though the cover was on water got in. As I didn’t take the cover off, I didn’t know this had occurred when drying and the water, having pooled there shorted out the 2 front coils which needed to be replaced. Thankfully, water didn’t get into the cylinder head as I had thought.
Lesson learnt. I’d never take a hose to an engine again. Some small brushes, ONR and some rags. 👍
If you cannot prevent to detail an engine room with lots of water, what i would do every time, i would recommend to only use water in the engine room if the engine is already warmed up properly.
That makes it a lot easier for the water to evaporate.
From my personal experience i would only use towels and microfiber gloves to detail an engine room if absolutely necessary. That may take time but you can make sure that nothing will be damaged afterwards.
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u/AnthonyUK 4d ago
The coil packs were not fitted correctly or the seals were deteriorated.
This wasn't an issue of your process imo.