Low compression, what does it all mean?

tc20

Hi all,
im just about ready to get my old merc back on the road. She's been lying up since December, mainly due to carb trouble. So i gets me a pair on ebay, only to discover they're not the mae west either. My mech worked with the 'new' set for ages, only to revert to the originals. He's stripped and rebuilt them, using some new carb kits i got, and reckons they're as good as can be. Im picking up the car later today, but on the phone he did mention low compression..:(

I should also include in this litany, that he has replaces all door seals and the front windscreen seal and chrome surround. When he took out the front screen, he noticed that the old screen was starting to delaminate, so suggested it would be better to fit a new screen. Ok, says i, collected the new screen, stored it in work for a week or so, but when i went to put it in my car to bring it up to my mech, i cracked the bloody thing..:mad:
So i get another new screen, thankfully this one is now fitted, and ready to roll.

Its been so long since ive been behind the wheel, i miss it so...

BTW, the car is a W114 230 saloon, and the engine is a straight six. So im wondering what can be done with a motor with low compression? Ok, it'll still run, but thats not ideal. Any help or info gladly appreciated, as always.

mike65

Low compression means new piston rings or valves seats/seals as a rule at least. How bad are the readings? It could be cheaper/easier to find a replacment engine.

Mike.

kyote00

low compression is not good.

At best, its 'just' the rings. to check this, do a compression test and find cylinder that has low compression, then drizzle a small amount of oil into the bore through the spark plug hole...the compression should be restored for a few turns of the engine...if it is then it most likely the rings....

It could also get the head gasket or a crack in the head...(depending on where the crack is --- check for oil in the water and water in the oil...)

At worst, its a worn engine that needs to be rebored....

As other posters mentioned, may be cheaper to get a new engine...

corktina

if it hasnt run for a while...the compression may improve after a few minutes......probably a faint hope only though....

tc20

Okay guys, heres the update..

collected my car yesterday eve, it was great just to get back behind the (LHD) wheel.. The job on the seals and screen is A1.
The mech has performed a leakdown test, and says that the valves are in pretty good shape (surprisingly, he added). Mileage is unknown, as its only got a 5 digit km clock. (Car is originally from Sweden). Mech reckons its also had the head done at some stage, theres a tiny loss on one side, but otherwise fine.
Now for the bad news - he reckons it'll need reboring plus new pistons
He said this is down to, most likely, galactic mileage, wear & tear. Now we didnt discuss pricing that job, (let me pay for this one first :rolleyes: ).
The body is in very good condition, ive got all new shocks, new front calipers
and assorted suspension bits. I have put a fair bit of hard earned into the car, so i would like to enjoy it for some time, before trading.
I know this is a bit of a piece of string question, but can anyone put a ballpark figure on the work? Anyone had similar done?

Cheers

RobAMerc

TC20 - May I suggest you look for a new engine ?

If you search the web there is a crowd that sell and deliver a refurb'd engine thats as good as new - (rings gaskets etc) and it will come with a guarantee.

I have found to my dismay that many people in this country (Particularly in the motor trade) see the fact you have something a bit different as an excuse to extort money from you.

If this isn't an option - keep an eye out on ebay - it never took me too long to get any part i was looking for on it ( Particularly ebay.de )when I had my w114.
I got the ecu unit for stg £20 including postage ( I was quoted €1000 locally ).

If you pm me I might even have the name of a guy who told me he had an engine for one he was driving he'd scrap for £100, might be worth a try.(Although its the Fi one)

8~)

Do you know for sure it's low compression?
Is it running alright. plenty of power, etc. Not using oil?

If okay, then drive and enjoy. If not, then go shopping.

corktina

yeah drive til it stops then get new engine....:cool:

tc20

Thanks for your replies lads...

@ RobAMerc - the mech who has done all the work on the car since i got it (just over 2years) is someone who i trust totally. The guy specialises in classics (he has a penchant for Saabs and racing 2CVs himself) and he knows his onions. He's has a passion for older metal, and is far from screwing me pricewise. He spoke to a colleague of his in the UK, (he's english himself) who is a merc mech, and his colleague said that these cars are known to just keep on going til theres nothing left. How long that could take, i dont know just yet. I'll be dropping up to him early next week to pay, and i'll get a much more indepth breakdown of the malaises :rolleyes: .. but thanks for the info, i may just call on you in the future!

@ 8~) - she runs ok. A bit lumpy idling at start up, and for a few minutes afterwards, but then fine. She's not using oil that i can see, tho ive only run it into work twice since i got it. I do always regularly check anyways.
Power wise, she's fine, considering its a 35y/o lump with unknown mileage.

Cheers

MercMan Ben

Hi TC,

The 230.6 was built with low compression heads and "normal compression" heads. Depending to which country it was delivered, to full fill the environmental exhaust laws...

If your engine is the low compression type, it might be ok...

How many bar does it show?

Regards,
Benjamin

tc20

Hi Benjamin,
and damn you and your technical expertise ....

Im not sure as to the technical breakdown results of the leakdown test, but i'll find out and let you know..
Interesting about the car being supplied with different heads. AFAIK, the car was originally Swedish

MercMad

Yes there were low compression engines so you would be best finding out and posting the readings before going any further !

Also the piston rings can seize through lack of use, and I have heard stories of other owners using there cars more regularly and imprving the situation !

My own 230 soldiered on for years and eventually I removed the engine, stripped it down only to find 3 broken rings !!

If your car does not use oil or smoke then I would not worry about it, and with all due respect I have heard folk blaming low compression for the inability to tune the car correctly !

Let us have those figures !

tc20

Thanks Ben,
i'll be up with my mech sometime next week to pay him the balance, and i'll get the info from him then. Im taking the car into work every second day or so, so she wont be lying idle