Yellowish-Brown Residue on Engine

Page may contain affiliate links. Please see terms for details.

Spinal

MB Enthusiast
Joined
Sep 14, 2004
Messages
4,806
Location
between Uxbridge and the Alps
Car
x254, G350, Duster, S320, Mach1, 900ss and a few more
Need some help,
finally got around to looking at the engine as there was some yellowish residue.

Residue (it's not as yellow as the image would suggest):
Screen-Shot-2015-05-04-at-18.58.30.png


Coil pack (there was evidence of water in the coil pack rubber)
Screen-Shot-2015-05-04-at-18.58.38.png


Also some evidence of water around the spark plug when removed:
Screen-Shot-2015-05-04-at-18.58.09.png


My first (worrying) guess was a leaking gasket to the coolant, but there's no mayo in the oil or the coolant that I can see.

Could it be just stagnant water? Any ideas?

I've cleaned the residue off, will try driving around a bit next weekend to see if it re-develops... but in interim, if someone can offer ideas I would very much appreciate it!

M.
 
There is plenty of information on Google.

Just do a search for Nissan yellow oil.
 
I think, steel tubes are used for spark plug wells and judging by the final pic they have been water logged and corroding - hence the residue.
 
Bellow: Water logged would make sense, the residue is dry and powdery - not oily at all. My first thought was a leaky gasket, but now I'm curious to know where the water came from as there's a lot of residue, so would suggest quite a bit of water...

Tec: Did that, but all the posts I found related to water in the oil - which isn't the case here. The oil appear uncontaminated.
 
What colour is your coolant...?
 
Dried coolant residue - meaning the engine possibly overheated at one time- could be for a variety of reasons ranging from a dodgy radiator cap to a cylinder head gasket/ cracked head
 
All alloy engine IIRC - so shouldn't discolour coolant as an iron motor does. Water more likely external and I suspect getting it's taint from the spark plug well tubes (which, have oil on their other side - if porous then oil can escape and water be ingested but the pressure differentials are slight).
The source of the water is a mystery (rain water blown in?) but there's a well created by the cam box shape to give any water ample opportunity to seep into the well.
 
Coolant is green... I tasted (yes) the residue, and it didn't have that sweet tang I expect from glycol...

Hoping it was an overzealous pressure wash by the previous owner now...

Will take it for a drive once I've flushed the coolant (did some work yesterday and lost a few litres of coolant, don't have "green" to top it up with, so will flush and replace). A little tempted to just put water in for the test drive... just to see if the residue comes back...

Cracked head is a worry, hopefully it's not that. Don't really want the expense of rebuilding the engine this close to the launch date...
 
Not coolant then - relief!
Looking at the pics again, and the proximity to the oil cap - leaking there and a film of oil emulsifying with whatever water/dampness it finds?
Check the oil cap seal and watch for it 'breathing' there with the engine running.
Straight water is fine at this time of year for short period. Remember you have diluted existing coolant when it comes to replenishing with AF/CI and adjust accordingly.

NB. The pic of the coil unit is telling us something. Residue on one side implies blown onto rather than submerged in.
 
Coolant is green... I tasted (yes) the residue, and it didn't have that sweet tang I expect from glycol....

Plus you are still with us :eek:
 

Users who are viewing this thread

Back
Top Bottom