So I'm looking for a possible project/sleeper car, the 1.8T is perfect, its incognito, relatively light, and has huge tuning potential (especially the AUM engine). So sorry for the long post in advance.

 

I've driven a potential one (2003., 290kkm/180k miles) and found a few possible major issues, as a newbie to 1.8T world, I ask for some heads up and insights about issues below:

 

1. idle RPM's around 1200-1400 when warm, turning engine off then back on, it starts at 800, then in a few seconds goes up to the mentioned 1200

 - quick google search show its probably the throttle body, at this mileage probably no cleaning helps but have to change whole unit which is quite expensive (~300EUR just the part) - is there anything else causing this?

 

2. slight jerk when feathering the throttle, it's almost unnoticeable, when accelerating just a bit more firmly there is no problem, only when coasting, when gas pedal is depressed and slightly pressed it hesitates for a millisecond then starts going normally

- coil packs? throttle body?

 

3. overheating when idling. When we stopped after the test drive and talked about the car more the temp started to rise. I tried unscrewing the coolant cap a bit, and immediately the level has gone up and quite loud air bubbling could be heard around the engine (as if it was full of air pockets), if I unscrewed it more the coolant would definitely go out the overfill.

- quick google search shows the 1.8T is infamous for poor cooling system, this case could be a broken water pump (last change over 10 years ago!!!), or worst case scenario head gasket - I fear the worst because of pressure in the system.

- the guys swears the last 1.5 years he owns it he never had any issues with coolant, he has never topped it up.

- during the test drive the engine is at constant 85°C - probably the temp sensor is also faulty

 

4. intermittent mechanical chirp around the pulleys and throttle body, as if a bearing or a motor is failing, is quite noticeable when cold but once it warms up its intermittent although present.

- motor from the throttle body, old pulleys?

 

5. slow cranking

- could be an old battery?

 

Apart from the above and a few other mileage related issues, the engine runs perfectly smooth, the turbo sounds healthy, there is no smoke on startup or acceleration, gearbox and clutch work smoothly, it really drives exceptionally well. I'm aware it's a time bomb because of the timing belt and waterpump, but if it turns out it's not the head gasket, I'd go for it, what do you think? What else should I look after in a high mileage 1.8T, and is it such a money pit?

I have a 2002 octavia 1.8T which has same type engine as one you mentioned.

 

1. idle should be lower when warm (cca 800rpm) - on cold start (even on not completely cold start) until secondary air pump runs to help warm up catalizator quicker 1200 rpm is normal (usualy for 30-90 second) then goes to 800 rpm

 

2. throttle body - cleaning, recalibrating -> vag com

   when coil pack is dead or bad you get knocking and warning light for sure - ussualy when on boost - and running on 3 cylinders

 

3. overheating? -  default needle should show top position 90 degres -> factury programed to show 90 although temp is between 75 and 105 degres(check on vag com) - > can be unlocked to show real  temperature without factory compensation

    how much does the temp rise while stationary?

    as far im aware some bubbling is normal when water is push back to expansion reservoir - it does operate under some pressure.

    when pump fails youre definitely going to overheat

 

4. you might get some strange noise when you start engine (only for a sec or so) - before hydraulic spanner does its work

   other noise is charcoal canister - clicking noise when removing petrol fumes 

 

5. most probably old battery - maybe also bad starter

 

you might not know these cars have a DMF (dual mass flywheel).

 

mine octy is sitting on 315k km at the moment it has a custom map 211hp an 330nm from 220k on - works like a charm now. i do spoil her with new oil every 10k plus all regular service.

always wait till oil gets warm then make a good use of calvary and let it cool down afterwards.

 

At this milage some parts of suspension should have probably been swapped. if all is good you should have a pretty good feel of the car on sterring wheel.

 

chech for air con, abs, door locking - unlocking, rust

 

 

 

 

 

 

 

   

 

 

If you find spare time come abroad. Have a vag com to address some of the concernes you have.

 

For the temperature, you say it's overheating but there's conflicting info: 

 

1.  Is the temperature gauge actually moving up past the 90º/middle position? If this is the case, are the fans also coming on?  

2.  Is the temperature gauge under reading, say 1/4 up the gauge whilst driving but then after idling will go up the 90º (or above) and drop again when you pull off? 

 

A common point of failure is the engine temp sensor; VW group issued a warranty replacement for the stock temp sensors (at the time).  They should have a green connector, the stock ones had a black connector and are prone to failure.  If you do replace this then go OEM, don't try to save money on cheap parts.  If the car is overheating e.g. going past the 90º mark AND the fans are coming on then it's more unlikely to be the temp sensor and you could be looking at a dodgy water pump (but it get's expensive at this point so get some advice and get a proper diagnostic).  Head gasket is another possible cause but there's other things that a far more likely. 

 

The thermostat is another possibility; if it's going past the 90º mark then it could be stuck closed, if it's not getting up to temp whilst driving but then slowly getting to 90º when idling then the thermostat is stuck open.  Again, get an OEM part, anything else is false economy.  Try the temp sensor first though, if you can't get a diagnostic done as it's cheaper and the usual point of failure. 

 

If you can it's worth getting a diagnostic scan, with VCDS or similar as you can check the relevant module to see what temp actually is compared to what the gauge is showing. 

 

I've just had a cooling problem with a mk4 Golf GTI with the 1.8T AUM engine. Temp wouldn't rise whilst driving but would increase whilst idling and then drop again.   I initially changed the temp sensor myself , which didn't resolve the issue, so I changed the thermostat.  This didn't work.  I took the car to a local independent specialist to help me out, it turns out, whilst I fitted a OEM, new temp sensor it was actually faulty (very bad luck and the first one the mechanic had ever seen!). So fitted another new temp sensor and it fixed the issue.  The thermostat's are prone to failure after 15 years anyway so that's one less thing to worry about 

 

 

@robek85 @penguin17 for the overheating I immediately parked the car and shut it down, the temp was rising quite rapidly, to about 110°C in two minutes. I didn't hear the fans coming on but didn't really look at them at that point, and during the test drive the temp remained "rock solid" at 85°C, so just a bit under the middle 90° mark. This for me is a bad sensor (had the exact same issue on my Oct TDI).

 

The guy swears he had no overheating or coolant issues... But I can see the coolant is blue instead of red, and its fresh.

 

While it was idling, before I noticed the overheat problem, I turned on the AC to LOW, and it didn't blow cold air (although outside is around 0°C), just mild warm air. Could be the AC was off by default when overheated.

 

@robek85 thanks for the invite, if this project lives I'll give you a call. And yes, I'm aware these cars have DMF's, thats why I'm super careful as when I bought the Oct TDI, the chirping I thought was a pulley was actually the DMF. Btw, I'm also looking for similar power output, around 220hp.

 

I forgot to mention in the original post - there is a plastic clicking sound coming from the steering column while turning the steering wheel. It's not the suspension or the steering rack, but 

inside the cabin, as if some plastic broke off and is scrubbing at certain angles of steering wheel. What could this be?

 

And I've just heard from a colleague that the exhaust valves are known to break on these machines? I presume the later versions such as AUM could be free from this?

 

Actually the only flawless part of the car is the suspension, it's really plush, no noise, clunks or anything, and dead silent over bumps.

 

Currently dropped the buy, the car in question is a money pit, the guy doesn't want to admit it (I reckon the guy himself dropped a lot of money in it just to make it run, now wants to bail out with least expense). I missed one '99 AGU 1.8T that seemed in very nice condition. The hunt is on.