This weekend's Ski's Z4 search question - Compression tests

Chanceschmerr

Chanceschmerr

Member
 Bristol, UK
Site Supporter
Hello again!
Thanks for the heated seats response everyone! I think I've got myself squared away with how to look at that.

A new question - I've kept in touch with a good friend and BMW enthusiast back in Canada, and he suggested that on a dealership-selling Z4, I should ask for a Compression test on the engine to get an idea on the piston ring state - i.e. better than 120 is good, under 120 and it could be burning oil soon.

I asked a dealership that has a Z4 I'm looking at, and their response was

Regarding running an engine compression test in close to 18 years of selling used prestige and performance cars I have never encountered someone asking me this (every day is a school day) we have a fresh MOT put in place. So the BMW would go the an emissions test. As I said I have never had someone ask me that, maybe that is common in Canada.

Am I crazy for asking, is it something that is not really asked for here in the UK?
 
Yup pretty crazy..why not pay a private mechanic to go along and do the test for you..

I think I've run out of credits on this one...bye!
 
B21 said:
Yup pretty crazy..why not pay a private mechanic to go along and do the test for you..

I think I've run out of credits on this one...bye!
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Alright thats fair. I'm only asking because I've not asked for one before in buying a car, so I'm not familiar how common it is to ask for one.

Bottom line- i dont know, so I'm asking.
 
B21 said:
Yup pretty crazy..why not pay a private mechanic to go along and do the test for you..

I think I've run out of credits on this one...bye!
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Pete, that was a little uncalled for.
He is asking a question, which, to us is a little unusual, but in Canada they have rather different testing schedules for vehicles and this may be more common there, particularly with trucks.

There is no such thing as a stupid question, but responses, that is a different matter.... 😉
 
Erudite-Idiot said:
Pete, that was a little uncalled for.
He is asking a question, which, to us is a little unusual, but in Canada they have rather different testing schedules for vehicles and this may be more common there, particularly with trucks.

There is no such thing as a stupid question, but responses, that is a different matter.... 😉
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Quite so..
 
Erudite-Idiot said:
Well they do say that accepting your failings is the main step to enlightenment, so there is hope for you sir 😋
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Knowing oneself, ones strengths, weaknesses, limitations and predilictions is never a bad idea and for many roles / jobs / relationships is a prerequisite!

Expressing one views is part of living a low stress life!-:)
 
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Chanceschmerr said:
Alright thats fair. I'm only asking because I've not asked for one before in buying a car, so I'm not familiar how common it is to ask for one.

Bottom line- i dont know, so I'm asking.
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So...

The underlying point is 'how far does a seller have to expend time and money on a non guaranteed sale and what is reasonable in today's market and given the age / type of car in terms of due diligence/'

Do these cars have a history of poor compression?

Why would a dealer spend maybe several hours of time doing this?

Do you want it done cold or hot?

Maye a borescope whilst there?

Have they had the engine oil sent it of for chemical analysis?

It was a £100k collectors toy..Ferrari 308 maybe?

£5k 23i/30i maybe not..IMHO
 
B21 said:
So...

The underlying point is 'how far does a seller have to expend time and money on a non guaranteed sale and what is reasonable in today's market and given the age / type of car in terms of due diligence/'

Do these cars have a history of poor compression?

Why would a dealer spend maybe several hours of time doing this?

Do you want it done cold or hot?

Maye a borescope whilst there?

Have they had the engine oil sent it of for chemical analysis?

It was a £100k collectors toy..Ferrari 308 maybe?

£5k 23i/30i maybe not..IMHO
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Right, and so this is the crux of my question - what is common and reasonable here, because I dont know.

I'm a naval architect, but by trade I'm a marine systems engineering officer, which means although I'm trained and knowledgable with a lot of what my stokers were doing on the diesels and gas turbines...
They never let me actually turn wrenches once my training was done. My job's to brief the captain as to why his frigate isnt sailing today 😂. (Probably) as a result of this, i was keen to learn and do as much maintenance/repairs as I could on my first car, the Tiburon - so thats what I did. However, although I'm familiar with compression tests, ive never done one, and the only two cars i've ever purchased were that Tiburon (found/vetted/negotiated in 2004 by the same friend who suggested the compression test!) and my Mercedes ML350 in 2016, and I didn't go that deep with it because it looked/drove immaculate to my eye.

The other impression i have is of my sale of that ML350 when I moved from Canada last summer. Had it on the market for a month at about $7500 CAD, and lots of hits but only a couple half serious guys. Then one day I get a message from a guy, wants to see it. He meets me at work, and no lie - he brings his own boroscope with him and a bunch of other tech with him, and he gives that car a more thorough diagnostic than the damn dealer ever did. After all that, he bought it at near asking, because aside from new tyres, not much else was needed. I do my best to keep my cars proper.

So this is my experience and where I'm coming from. I've seen guys go deep on a FB-marketplace listed car in the middle of a mulitstory car park, and I've seen guys buy it sight unseen. I was curious how it is here 🙂
 
Chanceschmerr said:
Right, and so this is the crux of my question - what is common and reasonable here, because I dont know.

I'm a naval architect, but by trade I'm a marine systems engineering officer, which means although I'm trained and knowledgable with a lot of what my stokers were doing on the diesels and gas turbines...
They never let me actually turn wrenches once my training was done. My job's to brief the captain as to why his frigate isnt sailing today 😂. (Probably) as a result of this, i was keen to learn and do as much maintenance/repairs as I could on my first car, the Tiburon - so thats what I did. However, although I'm familiar with compression tests, ive never done one, and the only two cars i've ever purchased were that Tiburon (found/vetted/negotiated in 2004 by the same friend who suggested the compression test!) and my Mercedes ML350 in 2016, and I didn't go that deep with it because it looked/drove immaculate to my eye.

The other impression i have is of my sale of that ML350 when I moved from Canada last summer. Had it on the market for a month at about $7500 CAD, and lots of hits but only a couple half serious guys. Then one day I get a message from a guy, wants to see it. He meets me at work, and no lie - he brings his own boroscope with him and a bunch of other tech with him, and he gives that car a more thorough diagnostic than the damn dealer ever did. After all that, he bought it at near asking, because aside from new tyres, not much else was needed. I do my best to keep my cars proper.

So this is my experience and where I'm coming from. I've seen guys go deep on a FB-marketplace listed car in the middle of a mulitstory car park, and I've seen guys buy it sight unseen. I was curious how it is here 🙂
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Nice defence may I say..!-:)

I would counter or humbly suggest proportionate and appropriate..

I was the founder and for over 10 years the primary manager in a special operations airline that conduct high In risk operations globally.

I held most of the key roles at one time or another..almost all approved / accepted by CAA/EASA and various ME states.

Including

Head of Engineering / Maintenance

Head of Continuing Airworthiness

Head of Flight Safety

Head of Ground Operations

Head of Flight Operations

Accountable Manager

But.. do I apply the same rigour and detail to my Z4 operations as I did to my duties there?

No..not even close..not by a factor of at least 10!

So my frustration and it is only my frustration is that the level of probing and insight in your research is at a level where indeed a CAA airworthiness auditor would be truly proud!-:)

Enjoy your search..but..I am out of here!-:)
 
I do feel you're overthinking it a bit.

Roof off + straight six = brilliant. Whether it's got heated seats or has had a compression test done is really not the point.

My first E89 was a poverty spec manual 30i. I didn't love the wheel style or the exterior colour, it had no heated seats, no idrive, but... see above re roof off and straight six. I loved the car.

Especially at the end of the market that you're looking in (no offence intended there, it's the same end of the market that I spend most of my time shopping in) you have to be prepared to compromise, be it on spec, condition or both. The last two cars I've bought both "needed" around 15% of purchase price spending on servicing/repairs. Neither are in my first choice of colour or have all the options I'd like, but they both had something about them that I loved and that made it worth compromising.
 
tiglon said:
I do feel you're overthinking it a bit.

Roof off + straight six = brilliant. Whether it's got heated seats or has had a compression test done is really not the point.

My first E89 was a poverty spec manual 30i. I didn't love the wheel style or the exterior colour, it had no heated seats, no idrive, but... see above re roof off and straight six. I loved the car.

Especially at the end of the market that you're looking in (no offence intended there, it's the same end of the market that I spend most of my time shopping in) you have to be prepared to compromise, be it on spec, condition or both. The last two cars I've bought both "needed" around 15% of purchase price spending on servicing/repairs. Neither are in my first choice of colour or have all the options I'd like, but they both had something about them that I loved and that made it worth compromising.
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Well said, and well appreciated. I don't mean to wear out my welcome, but to learn as I go to be a better Z4 owner, not just find the perfect buy.

I agree fully on the compromise and the heated seats discussion helped a lot, as rather than a full answer one way or the other, it showed me what I'd hoped - it is what you make of it. Could I survive without it? Absolutely. Is it nice to have? Also absolutely (until it breaks).
 
tiglon said:
I do feel you're overthinking it a bit.

Roof off + straight six = brilliant. Whether it's got heated seats or has had a compression test done is really not the point.

My first E89 was a poverty spec manual 30i. I didn't love the wheel style or the exterior colour, it had no heated seats, no idrive, but... see above re roof off and straight six. I loved the car.

Especially at the end of the market that you're looking in (no offence intended there, it's the same end of the market that I spend most of my time shopping in) you have to be prepared to compromise, be it on spec, condition or both. The last two cars I've bought both "needed" around 15% of purchase price spending on servicing/repairs. Neither are in my first choice of colour or have all the options I'd like, but they both had something about them that I loved and that made it worth compromising.
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Outstanding answer. Damn I wish I had written it! 😊
 
A compression test might be a fairly common practice in Canada but I've never known it to be done, or requested, in the UK.

IIRC you are looking at a 23i or 30i with the N52 engine which is pretty bulletproof. There are at least two members on here who have the same engine in their E86s that have gone past 200K miles. I've had the same engine in a 139K mile 325i and now in a 130K 330i and they both performed brilliantly, which probably wouldn't be the case if they were down on compression!

So on these cars it's not an issue IMHO.
 
Compression test is usually a diagnostic step done because you have a problem - I guess you could use that as a pre-purchase step, but agree with others - never done it - never heard of it being a 'thing' to request from a seller.

So yeh - I'm in the 'it's a weird thing to ask' camp.

An engine that fails a compression test would have obvious symptoms - rough running, clouds of burnt oil coming out the exhaust, hard starting, codes thrown, etc - all thing you can just see when you inspect the car.

Normally you see one of those things, then do a compression test to narrow it down.

But if you see one of those things when inspecting a car - maybe run away would be more appropriate & let the seller deal with the problem.

Hang on a sec - aren't you the guy that drove to Blackpool & spent hundreds of pounds to look at the most beaten up Z4 ever known to man from the dodgyest 'selling for a mate of my brothers uncle' seller?

& now you are worrying about a compression test?

Whilst you are there, make sure to do a full paint depth analysis, detailed underfloor probe, get the suspension & alignment professionally reviewed, have the heads removed & confirmed flat, injector output analysed, lab oil analysis, catalysts verified good, all sensors checked for tolerance, wheels removed & verified true / crack free. Inspect the age of all relays, confirm the cycle count of the roof / boot, get the plastic engine parts assessed for heat soak / aging, remove cam chain to assess tensioners/tolerances too.
 
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  • Haha
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matsmith749 said:
Whilst you are there, make sure to do a full paint depth analysis, detailed underfloor probe, get the suspension & alignment professionally reviewed, have the heads removed & confirmed flat, injector output analysed, lab oil analysis, catalysts verified good, all sensors checked for tolerance, wheels removed & verified true / crack free. Inspect the age of all relays, confirm the cycle count of the roof / boot, get the plastic engine parts assessed for heat soak / aging, remove cam chain to assess tensioners/tolerances too.
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I wasnt sure if anyone could make me feel dumber or more embarassed for asking an honest question, but you've succeeded. Thanks, i appreciate it.

As I've stated many times before, I'm new to these cars and I'm learning what's appropriate and what's not.
 
And for full disclosure - i went back to the friend who suggested i ask for a Compression test, to ask more questions about it, and he told me he asks for that when he buys BMWs to confirm that the engine is getting a regular oil change (infrequent changes - degraded compression).

Which, I wish he had been upfront with that reasoning when he suggested it, because I'd have just responded that proper maintenance documentation and the VIN Repair Report would tell me that information far easier.
 
Chanceschmerr said:
I wasnt sure if anyone could make me feel dumber or more embarassed for asking an honest question, but you've succeeded. Thanks, i appreciate it.

As I've stated many times before, I'm new to these cars and I'm learning what's appropriate and what's not.
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Don't feel too bad. No such thing as a dumb question. some of the answers however, whilst not dumb, can be unnecessarily harsh.
I read that post and after checking to make sure it wasn't posted late at night in an alcoholic haze I decided to treat it as humour rather than sarcasm. Let's hope I was correct.

One thing that did occur to me was; you could find an E89 that ticks a few of the boxes and use that to enjoy while you're over here, rather than waiting for the right one. You may find it suits you and you decide to keep it. If not, you are learning more by owning one, and have plenty of time to continue the search for your take home keeper.
 
It's been said before - firm but fair is my style (for good or bad).

I wasn't trying to make you feel dumb, but for a grown up with a history in the military you sure do have an 'unusual' approach.
 
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