Wednesday, 15 September 2021

E30 318i: Replaced AFM (Air-Flow Meter)

I’d been messing with my AFM in order to get the car running ok when cold and when I finally fixed the massive air leak on the inlet manifold I then struggled to reset the AFM back to standard. 
In order to get the M40 to idle ok while the engine was cold I adjusted the mixture setting to run richer. Obviously this was providing enough fuel to stop the engine cutting out while the plenum was filling with as much air as the cylinders could gulp through the gap in the manifold gasket. It runs and drives ok in this setting, but idles quite high (about 1100rpm) and you can smell the stink of neat petrol out of the exhaust. Ok for short trips shunting the project car around but will need addressing to enjoy it before summer ends!
The real problem began when I had repaired the gasket, got the engine running smoothly and then tried to reset the AFM back to a stock, or near stock value. To begin with I had been putting marks and taking photos to recall where the settings were before I started messing, but you know how it is, once you get immersed into a several day long tweaking session (take that as you will!) the tendency is to get lost along the way.
I gave up trying in the end and decided the only way to dial this engine in and be sure I was not fighting with a dodgy AFM was to buy one that had not been messed with. This is in my interests anyway, as I got one from a car with far lower miles on it so the carbon-track is less worn and I know the air-temp sensor is OK too, which was a doubt with the original one.

Sunday, 5 September 2021

E46 318i Touring: Replacing leaky Oil Cooler gasket [N42]

After fixing the major oil leak from the rocker-cover gasket [THIS POST], I noticed there was still some oil pooling on the under-tray and a fews spots dripping onto the road. I traced the source up the right side of the engine (looking from the front) and could see oil filling up some cavities in the cylinder-head to the left of the oil-cooler / filter housing, so determined this to be the culprit... yes, another common one, especially if the filter-housing has been removed for previous engine work.

A replacement gasket was just £6.59 from eBay and comes as a two piece set including the main gasket that sits between the housing and the cylinder-head, as well as a smaller gasket that sits between the oil-filter housing and the coolant fed heat-exchanger. This latter one hardly ever leaks, as it's very rare to find a filter-housing that has been split apart during engine work, but it's nice to have one anyway and you may find it worth the time to replace this one while the housing is removed, though I could not see any signs of leakage so didn't bother.


GUIDE:

1. Remove the lid to the air-con ducting that sits atop the firewall at the back of the engine by undoing the clips a quarter-turn, take out the pollen-filter and remove the weather-strip seal from the firewall.

2. Remove the air-con ducting itself by undoing the four screws using a T30-Torx socket and lifting it out.

3. Remove the rear right-side engine cover by undoing the two stud-nuts using a 10mm wrench.\

** Make sure you have a cloth / plenty of tissue to catch any oil that runs from the housing. **

4. Remove the three screws holding the oil-filter / cooler housing to the cylinder-head using a 10mm socket with a long extension bar. One is clearly visible in front of the housing, the other two being hidden down the back.

5. Lift the oil-filter / cooler housing upwards out of the head, catching any wayward oil and lift the housing clear, rotating it so as not to put too much strain on the coolant-hoses. The hoses do not need removing or any coolant draining for this job.

6. Remove the old gasket and clean both mating surfaces with a cloth and I find it always worth scraping any crud off with a razor-blade.

7. Insert the new gasket to the housing. A lug on one side sits in a notch in the housing so the gasket can only fit in one way. [If it's an older engine or the housing has been removed a few times before, it might be worth taking a belts-and-braces approach by applying some gasket sealant to the mating surface on the head, as I did with some white Corteco.]

8. Carefully place the filter/cooler housing back onto the cylinder-head, trying to spill as little oil as possible on the mating surface and reverse steps 4-1 to refit.