The 635 is an '86 Auto with 207,000 miles (not fault free) which I've had for nearly 6 years using as a daily, on more than off. When I got it the car was in a bit of an abandoned state and over the years it's been transformed into a fairly reliable old boat.
Last October it was running a bit on the poorly side, a bit lumpy and stinky of fumes and this came not too soon after the main relay had packed up. Consequently after all that 'trying to start it' the starter motor smoked itself and was replaced along with a fuel pump as the old one had a fractured outlet and was weeping fuel. The fuel pump was not new but pulled off the shelf and is from some older Bmw. It's was kind of an emergency swap but it works as far as I'm aware because the car runs/ did run fine on it.
During December one cold morning getting the car started was an issue after a long run in the rain the night before where it was performing 'ok ish'. However it started reluctantly and I moved it a few yards and parked it up for the day. That evening, it wouldn't start, well, it did but stalled soon after and then it refused to go at all. Further attempts saw the top blow off the air flow meter and that was that.
I carried out an all out assault on the engine management and found the following...
1) The air flow meter gave sporadic readings and lost contact with the track. This was adjusted to work and the spring tension was slightly adjusted to give as close as possible readings to the values I had available for this model of car. The operation of the gate was assessed as ok and it was reassembled.
2) The distributor cap had a bit of insulation broken away and a hairline crack so was swapped with a good second hand unit.
3) The plugs were removed and found to be fouled so were replaced for new plugs. The coil tested ok.
This got the car running but idle was unstable, fluctuating +/- 600rpm, sometimes stalling. This mainly occurred when the engine was cold but occasionally it would fluctuate and stall if left to idle for long periods when hot. So more testing was done.
4) The vacuum system was checked and a flexible joiner to the inlet was found to have perished and was split, this pipe comes from the deliberate air leak in the system in the cabin and it had a reducer (a bit of thick metal tube) inserted into the pipe, I guess this is to reduce any fluids from entering the pipe? The sensor which measures this leak is busted and I can assume it's always been like that whilst I have owned the car. The other two vacuum hoses, one from the fuel pressure regulator and one from the engine top breather appeared fine but all were replaced with silicone hose. This did not seem to have an effect on the running issues.
5) The Idle control valve tested out to be working and was clean but was replaced with new due to it being 30 odd years old.
6) The idle switch from the throttle had an enormous amount of travel before closing under throttle so was adjusted according to the information I have on the Motronic system so that it closes just as the throttle comes out of idle.
7) Slack on the throttle cable was taken up but is not resting pressure on the throttle mechanism
8) For piece of mind the thermostat was checked and found to be fully operational.
9) The coolant temperature sensor was checked and found to be operating well within it's listed parameters so was exchanged for a new one.
10) The throttle body was removed as it was gunked up with black slime so it was cleaned. The gasket between that and the inlet was suspected to be leaking so was sealed.
11) The inlet manifold to head was tightened but there is this strange occasional creak coming from it seems within the manifold itself when the engine is shut down, it sounds a bit like something is trying to close but is sticking?
12) I have not checked the speed or reference sensors operation but it is assumed that the engine would not run at all if these were faulty in some way.
13) I have disconnected the cold start valve and sealed it off to eliminate that from the running/ fuelling issues as they can get stuck open or the thermo time switch can be faulty
14) I have put in injector cleaner into the tank 100ml per 30L of fuel.
15) I have changed the coolant.
After doing all that it started well enough and ran well but occasionally the revs again fluctuated up and down, mainly when hot. Today I covered 50 miles to run it through and here are some notes...
16) Faultless for the large part in traffic and on the motorway, smooth and plenty of power, it still smells rich though, idle slightly hunting about when hot and in traffic +/- 50rpm but largely stable. After the run it was left to idle hot and the revs began to fluctuate +/- 500rpm from around 850rpm idle speed. I did notice that when they dropped to their lowest (about 250rpm) the temp gauge and rev counter flicked off and back on quickly, I suspect it's doing that because it is on the verge of stalling perhaps?
17) My biggest concern (and it might be paranoia) is that the cooling system appeared not to be pressurised after the run where as before and all through this work it has been. The pipes are very squishy and the gauge is reading full operating temperature, even worse is that giving it some revs like this produces a minor backfire which I've heard before on uber hot engines. Could changing the coolant from what was effectively water make a dramatic change in pressure charactistics?
There are no leaks except that the header tank is weeping as it's brass and could use reseaming but it's always pressurised before today? There are no signs of bubbles in the tank, the coolant level is good, the pressure cap is newish and there is no coolant produced from the overflow.
18) Engine oil (Castrol) is clean and clear.
So, is there any ideas of what also may be lurking that I haven't checked or have I completely missed the obvious? Because the next move is the dreaded compression test. (sad face).
EDIT: The intake hoses before and after the meter are in good condition, it is also running with a pipercross filter fitted around May time which initially produced good results. It may also help to know that if the idle is doing it's fluctuating thing then revving the car kind of clears it but driving a few yards definitely does clear it. I'm convinced it's over fuelling and flooding itself on idle. The fuel pressure regulator looks to be an original W.German item.
Just gone out to the car and noticed a strange pool of fluid under the passenger foot well (No air con on this). My initial thoughts were 'ok, bye auto box' but it turns out to be cold, clear, non flammable water of some sort dripping from the chassis rail. A look at the coolant pressure overflow pipe shows that water has run down this pipe whilst the car has sat doing nothing. The pipe runs down onto that chassis leg so I can assume that is the cause of the puddle on the floor. It doesn't smell of coolant really, it smells like its run over an engine though, kinda mechanical.
However, the car has been sat around for some months and there has been a bit of 'wet' work carried out on it. Is it standing water upset by todays drive? It wasn't there yesterday which suggests that the system has pressurised to the extreme whilst the engine is off which makes no sense. But then yesterday I barely got it over 40mph due to traffic, today was near on a tonne on private land?
This is the epitome of daily old car motoring...
Last October it was running a bit on the poorly side, a bit lumpy and stinky of fumes and this came not too soon after the main relay had packed up. Consequently after all that 'trying to start it' the starter motor smoked itself and was replaced along with a fuel pump as the old one had a fractured outlet and was weeping fuel. The fuel pump was not new but pulled off the shelf and is from some older Bmw. It's was kind of an emergency swap but it works as far as I'm aware because the car runs/ did run fine on it.
During December one cold morning getting the car started was an issue after a long run in the rain the night before where it was performing 'ok ish'. However it started reluctantly and I moved it a few yards and parked it up for the day. That evening, it wouldn't start, well, it did but stalled soon after and then it refused to go at all. Further attempts saw the top blow off the air flow meter and that was that.
I carried out an all out assault on the engine management and found the following...
1) The air flow meter gave sporadic readings and lost contact with the track. This was adjusted to work and the spring tension was slightly adjusted to give as close as possible readings to the values I had available for this model of car. The operation of the gate was assessed as ok and it was reassembled.
2) The distributor cap had a bit of insulation broken away and a hairline crack so was swapped with a good second hand unit.
3) The plugs were removed and found to be fouled so were replaced for new plugs. The coil tested ok.
This got the car running but idle was unstable, fluctuating +/- 600rpm, sometimes stalling. This mainly occurred when the engine was cold but occasionally it would fluctuate and stall if left to idle for long periods when hot. So more testing was done.
4) The vacuum system was checked and a flexible joiner to the inlet was found to have perished and was split, this pipe comes from the deliberate air leak in the system in the cabin and it had a reducer (a bit of thick metal tube) inserted into the pipe, I guess this is to reduce any fluids from entering the pipe? The sensor which measures this leak is busted and I can assume it's always been like that whilst I have owned the car. The other two vacuum hoses, one from the fuel pressure regulator and one from the engine top breather appeared fine but all were replaced with silicone hose. This did not seem to have an effect on the running issues.
5) The Idle control valve tested out to be working and was clean but was replaced with new due to it being 30 odd years old.
6) The idle switch from the throttle had an enormous amount of travel before closing under throttle so was adjusted according to the information I have on the Motronic system so that it closes just as the throttle comes out of idle.
7) Slack on the throttle cable was taken up but is not resting pressure on the throttle mechanism
8) For piece of mind the thermostat was checked and found to be fully operational.
9) The coolant temperature sensor was checked and found to be operating well within it's listed parameters so was exchanged for a new one.
10) The throttle body was removed as it was gunked up with black slime so it was cleaned. The gasket between that and the inlet was suspected to be leaking so was sealed.
11) The inlet manifold to head was tightened but there is this strange occasional creak coming from it seems within the manifold itself when the engine is shut down, it sounds a bit like something is trying to close but is sticking?
12) I have not checked the speed or reference sensors operation but it is assumed that the engine would not run at all if these were faulty in some way.
13) I have disconnected the cold start valve and sealed it off to eliminate that from the running/ fuelling issues as they can get stuck open or the thermo time switch can be faulty
14) I have put in injector cleaner into the tank 100ml per 30L of fuel.
15) I have changed the coolant.
After doing all that it started well enough and ran well but occasionally the revs again fluctuated up and down, mainly when hot. Today I covered 50 miles to run it through and here are some notes...
16) Faultless for the large part in traffic and on the motorway, smooth and plenty of power, it still smells rich though, idle slightly hunting about when hot and in traffic +/- 50rpm but largely stable. After the run it was left to idle hot and the revs began to fluctuate +/- 500rpm from around 850rpm idle speed. I did notice that when they dropped to their lowest (about 250rpm) the temp gauge and rev counter flicked off and back on quickly, I suspect it's doing that because it is on the verge of stalling perhaps?
17) My biggest concern (and it might be paranoia) is that the cooling system appeared not to be pressurised after the run where as before and all through this work it has been. The pipes are very squishy and the gauge is reading full operating temperature, even worse is that giving it some revs like this produces a minor backfire which I've heard before on uber hot engines. Could changing the coolant from what was effectively water make a dramatic change in pressure charactistics?
There are no leaks except that the header tank is weeping as it's brass and could use reseaming but it's always pressurised before today? There are no signs of bubbles in the tank, the coolant level is good, the pressure cap is newish and there is no coolant produced from the overflow.
18) Engine oil (Castrol) is clean and clear.
So, is there any ideas of what also may be lurking that I haven't checked or have I completely missed the obvious? Because the next move is the dreaded compression test. (sad face).
EDIT: The intake hoses before and after the meter are in good condition, it is also running with a pipercross filter fitted around May time which initially produced good results. It may also help to know that if the idle is doing it's fluctuating thing then revving the car kind of clears it but driving a few yards definitely does clear it. I'm convinced it's over fuelling and flooding itself on idle. The fuel pressure regulator looks to be an original W.German item.
Just gone out to the car and noticed a strange pool of fluid under the passenger foot well (No air con on this). My initial thoughts were 'ok, bye auto box' but it turns out to be cold, clear, non flammable water of some sort dripping from the chassis rail. A look at the coolant pressure overflow pipe shows that water has run down this pipe whilst the car has sat doing nothing. The pipe runs down onto that chassis leg so I can assume that is the cause of the puddle on the floor. It doesn't smell of coolant really, it smells like its run over an engine though, kinda mechanical.
However, the car has been sat around for some months and there has been a bit of 'wet' work carried out on it. Is it standing water upset by todays drive? It wasn't there yesterday which suggests that the system has pressurised to the extreme whilst the engine is off which makes no sense. But then yesterday I barely got it over 40mph due to traffic, today was near on a tonne on private land?
This is the epitome of daily old car motoring...