Thoughts please

[Tomk]

So my z3 2.8 1997 has compression issues (can’t remember which cylinder the garage said) the garage think it’s an exhaust valve, they even mentioned niskal (although I didn’t think z’s suffered, however it would be the right age).
What I want some thoughts on is, do I get it repaired knowing it’s all sorted or look for a replacement engine?
Any idea of the cost of getting a head rebuilt?

the car is not mint and i bought it as something I could clean up whilst using it, but didn’t bargain for a head rebuild.

cheers
Tom

 

[Tomk]

Will an auto boxed engine bolt straight up to a manual?

cheers.

 

[Zephyr]

You already have a manual engine, so yes, all the parts are already there.
depends on the price and condition of the engine you are going to swap.
it was removed for a reason and probably had issues unless it comes from a write off.
Swap another if in proper condition. And btw having an extra engine in the backyard is always nice when it comes to part hunting…

 

[t-tony]

If the crankshaft is the same it's likely to fit.

Tony.

 

[Tomk]

You already have a manual engine, so yes, all the parts are already there.
depends on the price and condition of the engine you are going to swap.
it was removed for a reason and probably had issues unless it comes from a write off.
Swap another if in proper condition. And btw having an extra engine in the backyard is always nice when it comes to part hunting…

The engines still in the car, the donor car is the same colour as mine so thought I might take some spares the break it.

still toying with getting the original engine fixed ‘better the devil you know’. But have kno idea of rebuild costs…..

cheers

 

[Ianmc]

still toying with getting the original engine fixed ‘better the devil you know’. But have no idea of rebuild costs…..

That would be my chosen route also if affordable.

 

[Zephyr]

One thing leads to another. Rebuilding an engine never goes as planned unless you are very strict on your budget and have a specific approach on the results.
many people including muself, started a simple gasket job and ended replacing valve seals, chain tensioners, theromostats, sensors, just because the engine was cracked open and it appeared as an opportunity for preventative maintenance.
my take on this, after many rebuilds, is to just throw in an engine that works and move on.
unless its a keeper, where rebuilding is the only way to go.
cheers

 

[PhilH67]

If you’re near Derbyshire I’ve an engine hoist and engine stand you could borrow

 

[D R Oldfield]

I have always been very weary of second hand engines many moons ago i bought a second hand ford xflow to fit in a mk1 escort it was worse than the one I took out even though I was assured it was a good one , I suppose it depends on a persons definition of what is good , personally i would always rebuild as once its done you have peace of mind and its something less to worry about

 

[Mike Fishwick]

Is the engine misfiring on that cylinder?

First make sure that the hydraulic tappet for that cylinder of not sticking, and preventing the valve from fully closing. If the engine has not had frequent oil changes the tappet could be sludged up, I would also change the oil to a good high-detergency diesel-type oil to clean away any sludge.

I had great sucess on a Golf GTi where a hydraulic tappet had locked when the engine was cold. I drove from Poland to Plymouth, then changed the oil to VW Quantum 15-40 mineral oil, and the problem went away in a week

The official BMW test for bore problems is to use a compression tester which does not record the maximum pressure, but reads the actual pressure as it leaks away, and check how long it takes for the pressure to leak down. I cannot remember the time or the end point pressure, but it is in the BMW manual on CD.

The next step would be to remove the cylinder head and look at the condition of the valve and seat faces.

 

[Stevo7682]

As @Zephyr has said if you pull the engine apart to fix one leaking valve before you know it its a full top end decoke new water pump etc ,etc.
As like he said you will take head off with a view to fixing one then look at rest and you'll think would be prudent to fix rest while off .
If you can do a lot of the work yourself fair enough can take some time over it but if paying for the job then costs would mount rapidly.
Also like said if a keeper maybe more worth the effort but if not then decent second hand unit toss it it and either go with it for a bit or move the car on for a new toy.
Stephen.

 

[Tomk]

Is the engine misfiring on that cylinder?

First make sure that the hydraulic tappet for that cylinder of not sticking, and preventing the valve from fully closing. If the engine has not had frequent oil changes the tappet could be sludged up, I would also change the oil to a good high-detergency diesel-type oil to clean away any sludge.

I had great sucess on a Golf GTi where a hydraulic tappet had locked when the engine was cold. I drove from Poland to Plymouth, then changed the oil to VW Quantum 15-40 mineral oil, and the problem went away in a week

The official BMW test for bore problems is to use a compression tester which does not record the maximum pressure, but reads the actual pressure as it leaks away, and check how long it takes for the pressure to leak down. I cannot remember the time or the end point pressure, but it is in the BMW manual on CD.

The next step would be to remove the cylinder head and look at the condition of the valve and seat faces.

Full service history, just did a service. Blue smoke under hard acceleration and very lumpy tick over.

Done all the usual rubber suspects, hence the compression test.

 

[Tomk]

As @Zephyr has said if you pull the engine apart to fix one leaking valve before you know it its a full top end decoke new water pump etc ,etc.
As like he said you will take head off with a view to fixing one then look at rest and you'll think would be prudent to fix rest while off .
If you can do a lot of the work yourself fair enough can take some time over it but if paying for the job then costs would mount rapidly.
Also like said if a keeper maybe more worth the effort but if not then decent second hand unit toss it it and either go with it for a bit or move the car on for a new toy.
Stephen.

that’s what I’m thinking, have water pump, thermostat waiting already .

 

[Tomk]

One thing leads to another. Rebuilding an engine never goes as planned unless you are very strict on your budget and have a specific approach on the results.
many people including muself, started a simple gasket job and ended replacing valve seals, chain tensioners, theromostats, sensors, just because the engine was cracked open and it appeared as an opportunity for preventative maintenance.
my take on this, after many rebuilds, is to just throw in an engine that works and move on.
unless its a keeper, where rebuilding is the only way to go.
cheers

Problem is I have know idea what to budget for! Thanks for the advice

 

[Tomk]

If you’re near Derbyshire I’ve an engine hoist and engine stand you could borrow

Thanks but miles away!

 

[t-tony]

Blue smoke is engine oil being burned through the combustion Chambers. Will not be split rubbers etc. Will be worn, or stuck piston rings. Worn valve stem oil seals will produce blue smoke on start-up.

Tony.

 

[Tomk]

Blue smoke is engine oil being burned through the combustion Chambers. Will not be split rubbers etc. Will be worn, or stuck piston rings. Worn valve stem oil seals will produce blue smoke on start-up.

Tony.

yep blue smoke on start up, seems to have got worse quickly.

 

[t-tony]

If mainly on start up it does sound like valve stem oil seals which become hardened with heat over time and lose their sealing ability. They can even break into 2 parts and then they leak really badly. I don't know for sure but it's possible that these may be able to be replaced without removing the cylinder head from the engine. It's possible on some engines and not others.

Tony.