SL280 problems

[liammc]

I've recently bought an SL280 which is my first merc and I'm well chuffed with it, faults aside.

First problem is I think its losing water. The manual I have is actually for an SL300 but it says the water should be right up to the collar in the header tank. After about 5-600 miles it has lost about 100ml and I top it up every time rather than see how low it gets. The exhaust gas is quite moist but only when running from cold.

Secondly the engine has a lump on idle. Happens every 5 seconds or so but the revs dont alter and I cant hear a backfire(however quiet) from the exhaust.

Last but not least, when it is idling the oil pressure gauge drops to about 1 1/2 bar. Pops straight up to 3 bar as soon as you touch the throttle, and when driving it never drops below 3 bar. Is this normal?

Any guidance appreciated, thanks.

 

[guydewdney]

the 1.5 bar is fine - 1 is the limit really... give it an oil change to be sure - decent semi synth imho...

try changing the plugs / cleaning them / re-gapping them (depending how tight you are... )

check dizzy?

clean throttle body?

i am surprised at the comment of fill to the top of the res tank - isnt there a mark on the side?

 

[Brian WH]

Never fill to the top, as the water expands when hot and will be pushed out the overflow under pressure. This accounts for the drop in water level.

Just leave it at 100 ml low and see if it gets any lower.

 

[liammc]

Well I did look for a mark, and refered to the manual when I couldn't find one. The oil was changed in a service 2k miles ago.

What should I be using to clean the throttle body - carb cleaner/WD40? Also is there a TPS or anything that must not be moved or any other risky components?

Cheers for the reply

 

[liammc]

Yep just checked the damn manual "The coolant must extend up to the shoulder in the filler neck.. which I did "....Refer also to mark (1) on the coolant reservoir." Thats where the black plastic meets clear plastic. OOPS! So maybe theres been a bit of excess pressure in the coolant sytem eh!

 

[Will]

As Brian has said, let it sit at this level for a while, and monitor it.

100ml is very little, and would easily account for thermal expansion.

Depending on what type of journeys/driving you do, check it every few days or so, and see what happens.

There should be a warning light anyway if it drops really low!

BTW, if you are using hard tap water to top it up each time, it won't take long to fur up the cooling system and dilute your antifreeze!

The moisture you describe sounds normal, most cars have a little condensation from the exhaust when cold, especially when fitted with a cat (water vapour is one of the by-products IIRC)

Good Luck,

Cheers,

Will

 

[liammc]

Ok cheers. So I presume your recommending distilled water? Do motor factors generally sell it?

 

[liammc]

Sorry forgot - I mixed up 5 litres of 40% antifreeze in a drum and have been using that

 

[peterchurch]

Hi,
the other thing to check if you think you are losing coolant is the oil. If there is any sign of curdling then you may have a very small leak in the head gasket. I do hope not, and for the amount of water you are talking It does not sound like it but it would be better to catch it now if it is

Cheers,

Peter

 

[liammc]

No mayonaisse in the oil which may be a good sign. I'll just keep an eye on it for a month or so. These engines are prone to head gasket failure more than any other fault....is that right?

 

[liammc]

I also forgot to mention something else:

When I floor it, with the kickdown switch or not, it pulls pretty well, up to about 4k revs then it takes off like a fappin turbo kicked in or something Do they have any variable valve timing or extra injectors, anything like that? Just wasn't sure if the performance should behave like this right through the rev range.

Cheers

 

[peterchurch]

Hi,
I believe the old straight 6 engines were vvt where as the new V6 is not. not sure about the 2.8 but I would guess if you are getting second legs at 4k that would be VVT kicking in

Best regards,

Peter

 

[liammc]

Yeh it definitely 's And the noise has a big factor I actually considered ordering a stainless exhaust from mercedesperformance.co.uk but the price is extortionate. /just wait till he buys an oem one they say

 

[peterchurch]

Yeh it definitely 's And the noise has a big factor I actually considered ordering a stainless exhaust from mercedesperformance.co.uk but the price is extortionate. /just wait till he buys an oem one they say

If you want a sports exhaust talk to hayward and scott in Essex

link
H & S

MR2 Owners Club

£470 for a bespoke twin exhaust sounds rather good to me ;-)

 

[Vlad]

How old is your car?....is it the straight 6 or the V6?

If its the straight 6, there are a couple of things you can do to cure that stumbling idle.

Let me know which engine you have.

 

[frog1520]

How old is your car?....is it the straight 6 or the V6?

If its the straight 6, there are a couple of things you can do to cure that stumbling idle.

Let me know which engine you have.

Hi mate! I'm interested in that, what would you recommend for the straight 6?

Cheers!

 

[liammc]

Thanks, that would be greatly appreciated. Its a '95 straight 6 engine.

 

[glojo]

Hi,
the other thing to check if you think you are losing coolant is the oil. If there is any sign of curdling then you may have a very small leak in the head gasket. I do hope not, and for the amount of water you are talking It does not sound like it but it would be better to catch it now if it is

Cheers,

Peter

An excellent point, and also check your water as well to see if there are any traces of oil.

I do however agree with all the excellent points raised. Water expands and it has to escape somewhere. Hard water is a problem and it certainly will cause furring in the long term.

You certainly have purchased a very nice vehicle.

Good luck,
John

 

[liammc]

Cheers, the water is clean as is the oil. Does a compression test work accurately on these engines? TBH I've never heard of hard water being a problem, makes sense now that its been mentioned mind you.

Thought I should mention that in normal driving it runs about 85-90deg but when driven hard it increases to just short of 100deg, tis this normal?

When changing the coolant are there any guidlines to follow i.e. is it bad for air locks etc? Just that I dont believe my Merc garage would be bothered about using distilled water on an older car, so would consider doing it myself if its easy, especially as winter is approaching.

Thanks for the response folks

 

[peterchurch]

Hi,
my 320 runs around that too, as did most of the cars I test drove so I would think that it sound about right

Peter