Monday 31 May 2021

E30 318i M40: Bosch injectors and tips - checking condition

Next on the agenda to find the culprit of the rough running and stalling idle was to examine the injector condition and the plastic tips. The injector bodies are quite rusty and corroded so they could well be the original set, but on closer inspection the tips are fine and they look to be in pretty good condition, so onwards.

To inspect the injectors the lower inlet manifold will need to be removed, which involves de-plumbing the fuel lines and some of the water hoses. 

E30 318i M40: Camshaft and valve condition

I whipped the rocker cover off to check if there was a dropped valve or broken spring that might be contributing to the poorly idle, but no such defect found. In fact, this has to be one of the cleanest top ends I have ever seen. Nice!

BMW E30: Digital Clock quick LED upgrade

The bulb had blown in my E30’s digital clock, so I decided to repair it with a quick and easy LED upgrade. It’s another bulb load of power taken off my 35 year old dash wiring so can’t hurt. 

The bulb-holder is integral to the working of the lamp, with the metal clips that hold it in place also acting as live/earth contacts. LEDs built into such a holder can be purchased specifically for replacing bulbs like this if you want to go that route, but if you have a bunch of cheap LEDs lying round and don’t want to spend any money then read on.

Simply remove the plastic holder and cut the old bulb away from the two pieces of metal. Solder a cheap yellow or red LED onto the metal contacts in the place where the bulb was attached and bend the LED stalks back on themselves so the diode is pointing the right way, as in pic. A pure-white LED would probably be better, but they use more wattage, will probably require a spend and cheaper dome LEDs work fine anyway.

The bulb for the clock has a resistor built in anyway, so the LED will run fine and not pop without modification, but if you find it is too dim or bright to you can ‘piggy-back’ another resistor across the stock one to raise or lower resistance to suit. A calculator to help work out what resistance you need are easily available online, but trial and error is best if you have a bunch of LEDs / resistors lying round.

You may want to cover the recess at the back of the clock with electrical tape to stop light spilling out.

E30 318i M40: Misfire and self-revving - symptoms of major induction air-leak

This video shows the symptoms of an air-leak in the induction system, where unmetered are drawn in after the throttle-body causes a terribly poor idle, a permanent misfire and the engine to rev itself gently. The tendency is to look at the ICV (idle control-valve), ignition coil, AFM (air-flow meter) etc., but chances are it will be an air-leak on the induction. In this case it turned out to be a damaged and disintegrated gasket where the lower inlet-manifold mates to the cylinder-head. 

Sunday 30 May 2021

BMW E30 Heater Matrix Hoses Configuration - Right and Wrong way round + how to bleed matrix / remove air-lock

My E30 had little or no hot air from the blower inside the cabin. I have heard it is common for the two hoses running to the heater matrix to be fitted back to front, so the flow of coolant through the core is reversed. This causes air locks and severely reduces the amount of coolant flowing through the heater matrix, thus no hot air. 

The reason these hoses so often get fitted incorrectly is due to their location and the way they look when fitted. It appears obvious that the upper hose (back of cyl.-head to heater) goes to the upper stub on the heater-matrix and the lower hose (side of block to heater) goes to the lower stub on the matrix. The hoses look happier this way round, but the matrix and heater-valve are designed in such a way that flow is interrupted and causes the air-lock. 

The correct way round is actually with the upper hose connected to the lower stub and the lower hose to the upper stub, which does of course appear to be back to front, but is essential for correct flow of coolant round the whole engine, not just the heater-core. The correct and incorrect hose configurations are shown in the pictures below.



How to Bleed system and remove air-lock from Heater-Matrix:

** This is not the normal air-bleeding process when refilling an empty system with coolant, this process is to bleed a system with the air-lock at the back of the head and / or the heater-matrix full of air. **

1. Ensure heater-matrix hoses are fitted the correct way round, if not swap them over. [You should notice if there is an air-lock that no coolant comes out of the hoses when removed from the matrix and the stubs appear dry].

2. Fully tighten the lower [inlet] hose.

3. Leave the upper hose disconnected from the matrix. 

4. Remove the radiator bottle cap. Assuming the coolant level is up to the halfway / max. mark, there should be some gulps of air and the coolant level should drop slightly in the rad. bottle.

5. Cut the bottom off a 2-litre drinks bottle and fill it with water, holding your hand over the lid.

6. Dump the water from the drinks bottle into the radiator bottle, allowing the weight of water to push the remaining air though the system. Water should start to come out of the upper heater-matrix hose from the head. Block this hose with a finger.

7. Continue to top up the radiator bottle with water until water begins to flow out of the upper stub on the heater matrix and quickly refit the upper hose, which can now be fully tightened.

8. Drain the radiator bottle back down the halfway /max. / fill line.

** You should be good to go, but can now bleed / top-up the system using the usual bleeding procedure if necessary. **

Wednesday 26 May 2021

BMW M40 Engine - how to check timing, where the marks are located

This must be one of the hardest bits of info to find in the whole world of BMW, but there is a great post on BMW Werks on how to do it [].


** Only if crank pulley has NOT been separated from crankshaft! **

1. Remove the distributor / timing cover at the front of the engine.

2. Check the timing mark on the crank pulley. This is an arrow cast into the block which should line up with the sprocket tooth to the right of the gap in the teeth, as in pic below.

3. Check the timing mark on the camshaft pulley. This is a notch/line mark in the pulley and should line up with the right-angle notch in the cylinder head, as in pic below. If this looks good, your timing is fine.

Thanks again to xdrian on BMW Works for making these pics and sharing this secret!

Monday 24 May 2021

E30 318i: New Bosch spark plugs + correct coil fitted

With the car still misfiring a bit, I turned my attention to the plugs and HT leads. All appear fine. The coil works because there is a spark. I inspected the plugs, a set of NGK R that don't look particularly ancient, expecting one or more to be wet with unburnt fuel from a combination of misfiring and running an over-rich mixture from tweaking the air-flow meter [AFM]. I noticed that the plugs were in fact all dry and totally black with soot at the tips from over-fuelling, but their condition seemed fine. This matched the points in the distributor-cap, which were also blackened.

The spark plugs were working, but they didn't seem to fully igniting the mixture and performing weakly, so I turned my attention back to the coil. A previous owner had fitted a universal 'Sports coil' and judging by the shiny casing it doesn't look too old, so I couldn't see how it could be at fault. Thats when I noticed the terminal connecting it to the HT lead. It's about 10mm wide and has a metal inner lining. There is a screw at the bottom holding it in. This is obviously designed for a different type of HT lead than fitted to BMW, as the lead has a rubber plug where

it contacts the copper casing of the terminal in the coil. The metal terminal in the HT lead is designed to fit over a stud inside the coil-terminal, which is what I've always seen before, not just in BMW. This means the only contact being made by the main HT lead was its very tip touching the screw at the bottom of the coil-terminal.

I swiftly ordered a used OEM Bosch coil unit from eBay for £15. A 'Sports coil' type with the correct end was about £35, but I figured it was best to go original, at least for the time being while I iron out the M40 engine's running problems. While I was at it, I bought some OEM Bosch spark plugs for £13, which is cheap and I thought I may as well rule out plug condition as a factor with not knowing how long the incorrect coil has been fitted to the E30.