Disco 2 A/C bogging down engine

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Michalis Karatzis

Michalis Karatzis

Active Member
Posts
189
Location
Cyprus
Hi guys, I am trying to solve a problem with my 2000 Disco 2 Td5 Auto (10p). Pulling away is very very slow when the A/C is on (see vid where I try to accelerate from stationary but the rev counter moves super slow). The reaction from the engine is very lethargic from idle to 1500rpm and then suddenly it goes.

Any ideas? This only happens when the A/C is on. When it's off taking off is fine.

 
Last edited:
Michalis Karatzis said:
Yes and also other sensors were either replaced or checked or disconnected (MAF, FT, ECT etc). No fault codes either.
Click to expand...
Then it really does sound as if there may be a fault with the AC pump causing massive drag on the motor. If you could possibly get a known good one and swap them over. but due to the need to be careful with the AC coolant this could be difficult. Is the AC working normally?
There amy be another electrical fault which I wouldn't know about as I am too old skool for all that?
 
Michalis Karatzis said:
What can cause so much drag from the A/C? Too much/little oil/refrigerant in the system? Or could it be an electrical issue?
Click to expand...
Michalis, I have no idea as I have never had the problem before, but if the only difference between it running fine and it not running fine is when you switch on the A/c then it has to be either the A/c pump or some electronics connected to it, telling the engine not to rev up propelry for some reason, and with Canbus who knows? Apart from some electronic genius who hopefully will jump on soon.
 
Iirc on the td5 when you mash the go pedal it switches off the a/c pump temporarily?
Try and find the discovery workshop manual and have a read.

This was a real bad issue on 300tdi manuals with a/c, get a load on and try and pull away up a hill forget it!
 
Remove fuse F6 engine bay and see how it goes then... if the symptom goes away the problem is with the compressor, might be low on oil or some other internal issue which makes it turn hard. If the problem persist with fuse removed then it's some other thing and check how much the voltage drops when you switch on the aircon
 
sierrafery said:
Remove fuse F6 engine bay and see how it goes then... if the symptom goes away the problem is with the compressor, might be low on oil or some other internal issue which makes it turn hard. If the problem persist with fuse removed then it's some other thing and check how much the voltage drops when you switch on the aircon
Click to expand...

Removing F6 isn't the same as turning the a/c off or unplugging the connector to the compressor? I have done those 2 and power comes back. I will check the drop of voltage on nanocom when turned on.

Any guidance on how to refill the oil in the compressor in case is overfilled? I read Rave and the equation it provides is based on the assumption that you have the correct amount in the compressor already (Y in the equation below).

X the amount of oil in new compressor
Y the amount of oil in existing compressor
20ml in the rest of the system
Q the amount to drain from new compressor

X-(Y+20ml)=Q
 
Michalis Karatzis said:
Removing F6 isn't the same as turning the a/c off or unplugging the connector to the compressor? I have done those 2 and power comes back. I will check the drop of voltage on nanocom when turned on.

Any guidance on how to refill the oil in the compressor in case is overfilled? I read Rave and the equation it provides is based on the assumption that you have the correct amount in the compressor already (Y in the equation below).

X the amount of oil in new compressor
Y the amount of oil in existing compressor
20ml in the rest of the system
Q the amount to drain from new compressor

X-(Y+20ml)=Q
Click to expand...
Are you talking about the amount of oil you would put in the refridgerant?
 
If you have any doubts at all I'd take it to a professional A/C specialist who, I believe, will not only evacuate the old refrigerant, but will then flush the system and then refill it.
In the past I have clamped the flexible hoses to the pump, replaced the pump with a second-hand one, fixed the hoses back on, released the clamps and then topped the system up with a kit I was able to get from Halfords which included a gauge, a gun and a bottle of refrigerant ready mixed with oil, in the right proportion.
If you cannot get a kit, you could do as I did up to the point of topping up then take it to an A/C place to get them do what I mentioned above.
Is it possibly a question of a bearing in the compressor that needs lubricating or changing or does the compressor simply have too much friction due to wear?
Best of luck!:)
 
Removing F6 is like when you unplug the clutch so if you did that and it's OK that way the problem is with the compressor, i have no ideea how to fix that other than go to specialists
 
Michalis Karatzis said:
Removing F6 isn't the same as turning the a/c off or unplugging the connector to the compressor? I have done those 2 and power comes back. I will check the drop of voltage on nanocom when turned on.

Any guidance on how to refill the oil in the compressor in case is overfilled? I read Rave and the equation it provides is based on the assumption that you have the correct amount in the compressor already (Y in the equation below).

X the amount of oil in new compressor
Y the amount of oil in existing compressor
20ml in the rest of the system
Q the amount to drain from new compressor

X-(Y+20ml)=Q
Click to expand...


The oil is called pag oil, it is on the gas side of the system, various visocities/quantities depeending on applicaiton and parts replaced, they will have a book telling them how much oil per car.
The stick their machine on and it extracts the gas and the remaining oil, the oil is measured, they hold vac for x period of time, if okay they add correct amount of oil then the gas.
 
That sounds very odd? Even with the aircon pump working flat-out, you ought to only be a couple of horsepower down. Do you get horrendous belt squeal or a smell of burning belt when this happens? I haven't a clue about Discos or the TD5 engine, so this is all guesswork, but it doesn't seem like drag on the aircon pump. Does the aircon work OK at idle? Does it also work OK when you're doing more than 1500 RPM (e.g. cruising along the motorway)? I know some cars can do clever things with the engine management system and aircon (e.g. cutting out the compressor at full throttle), and I'm wondering whether the TD5 does something to turbo boost? It's almost as if your engine management system is dropping the engine output when the aircon is on.
 
Avocet1 said:
That sounds very odd? Even with the aircon pump working flat-out, you ought to only be a couple of horsepower down. Do you get horrendous belt squeal or a smell of burning belt when this happens? I haven't a clue about Discos or the TD5 engine, so this is all guesswork, but it doesn't seem like drag on the aircon pump. Does the aircon work OK at idle? Does it also work OK when you're doing more than 1500 RPM (e.g. cruising along the motorway)? I know some cars can do clever things with the engine management system and aircon (e.g. cutting out the compressor at full throttle), and I'm wondering whether the TD5 does something to turbo boost? It's almost as if your engine management system is dropping the engine output when the aircon is on.
Click to expand...
I can see where you are coming from. Mine did this sorta thing until I cleaned the MAP sensor, then it was OK. Which is why I asked OP if he had done that. Maybe his MAP is fubar. but it is a very funny coincidence that it only happens when the A/C is switched on. Maybe there is a dodgy connection in the wiring to and from the switch to the A/C and this is sending some sort of a funny signal to the engine's ECU. As you know, I know F all abut all the CANbus cr@p!
 
Avocet1 said:
That sounds very odd? Even with the aircon pump working flat-out, you ought to only be a couple of horsepower down. Do you get horrendous belt squeal or a smell of burning belt when this happens? I haven't a clue about Discos or the TD5 engine, so this is all guesswork, but it doesn't seem like drag on the aircon pump. Does the aircon work OK at idle? Does it also work OK when you're doing more than 1500 RPM (e.g. cruising along the motorway)? I know some cars can do clever things with the engine management system and aircon (e.g. cutting out the compressor at full throttle), and I'm wondering whether the TD5 does something to turbo boost? It's almost as if your engine management system is dropping the engine output when the aircon is on.
Click to expand...

I was also thinking that the belt should struggle with so much resistance but it seems to cope ok. No squealing, no burnt rubber. When cruising on the motorway you can definitely feel the strain on the engine when the a/c turns on but it's not as pronounced as when taking off. On the other hand it does drop a gear when the motorway has a small incline...an issue I have been chasing for some time. (now the a/c situation explains it). Without the a/c on it travels much smoother on the motorway.
 
Update

Issue was resolved today (I hope this is final). Timing was off by a hair and this made a huge difference after fine tuning it. Power was significantly affected at low rpm and when the ac was on it "killed" the engine. So lesson learnt.
 
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