Which SL 3.5 or 3.7.

[AndyP]

Hi,
I am looking at buying an SL 350 but not sure which engine to go for. The 3.7 has the 5 speed box with the 3.5 having the 7 speed.

I would appreciate any feedback and advice on which one to go for.

Also any problems these cars may have, the only one I have heard of is the fuel tank on early 3.7 models. Also rear arches I am told tend to rust.

Thanks.
AndyP.

 

[RAJ55]

From my knowledge;


3.7 m112 engine – no major engine issues
3.5 m272 engine – balance shaft issues can cost up 2k to repair


Known problems are water leaks which lead to other problems, PSE pump etc. Others are SBC limit, fuel tanks rattle, rust on rear arches and ABC suspension pump if you have it.

 

[clk208]

The m272 3.5 are more fuel efficient and throw out quite a bit more power than the m112.

The balance shaft issues shouldn't be a problem from early 07 onwards, and a later car less likely to rust.

Both silky smooth, a pleasure to drive and sound great though.

 

[AndyP]

Thanks for the feedback, I would appreciate anyone else who has an opinion on the SL350.

AndyP

 

[frank dolan]

Hi, I have a sl 350, the problems I have , are a leak in the boot , and a creaky roof. What year are you looking at.

 

[AndyP]

Hi,
I am not sure as yet. Was thinking of a 3.7 pre 23/03/06 to avoid high road tax. However I am getting drawn to an 07 3.5 model albeit with the higher tax of £475. I was hoping for some feedback on both cars from owners of each one. It all depends on condition and spec an of course price. I was thinking of around £14000 as a budget but could stretch to 15K or 16K for the right car.
Regards.
AndyP.

 

[Drew sl]

Hi iv got 03 350 3.7 the engine been fine had change thermostate that was easy to do. Had own the car a year now. Fuel not too bad can get 25mpg if you give beans and driving slow. 5 speed gear box is nice, make sure oil level is right you get probelms. Make sure rear drains are clear on the boot. They do take alot too maintain, got trans oil dipstick and engine oil. The car always put smile on your face

 

[Drew sl]

Hi iv got 03 350 3.7 the engine been fine had change thermostate that was easy to do. Had own the car a year now. Fuel not too bad can get 25mpg if you give beans and driving slow. 5 speed gear box is nice, make sure oil level is right you get probelms. Make sure rear drains are clear on the boot. They do take alot too maintain, got trans oil dipstick and engine oil. The car always put smile on your face

 

[grober]

Only other thing to check is whether the car has ABC active body control or conventional suspension [ 6 cylinder cars only??] ABC can give problems which are expensive to fix if they go wrong.
https://en.wikipedia.org/wiki/Active_Body_Control

 

[MikeInWimbledon]

I have the 5 speed 3.7 2005 SL350, which replaced a 2003 SL500 as my day to day runaround

I think it's a fabulous car - nippier and lighter than the V8 SL500. The only reservation is that I would have preferred the option of ABC suspension which was standard on the SL500. (Other opinions are available).

I bought it because it belonged to an ex-colleague who had owned/garaged it for 10 years. I'm more than happy with it.

I struggle with this Interweb nonsense about faults with specific engines. Most people don't have any trouble with their Merc engines, unless they're either high mileage or "low mileage on the clock / high mileage under the hood."

The only way to decide is to look in your wallet and see how much money you want to spend, on what kind of mileage / condition.

Money wasn't an issue for me, I could easily have spent twice the amount on a facelift 2008 car - but I just picked up this lovely 2005 car because of its provenance and colour.

(The mpg difference between the 3.7 5 speed and the 3.5 7 speed is insignificant compared to the cost of running the car overall.)

The only problem worth worrying about is making sure that the rear boot seal is good, and that "you" don't tip loads of water into the boot every time you go into it. Well documented and easily investigated.

 

[Drew sl]

Mine is coils springs cost cheaper if goes wrong. Think the v8 have the ABC kit on cost loads if goes wrong. Had a drive in sl 500 before that felt very strange to drive, alot lighter on the front than the 350. It did have strange tyre size set up could be that.

 

[oldguy57]

We have an 04 3.7 - a great car and doesn't disappoint in any respect. Look at a few before buying , there are loads out there. Water leaks in roof and boot are easy to spot but not that difficult to solve. Rust round rear arches and bubbling of paint on roof corners are common(ish). Other than that maintenance history and usual stuff. Most seem to have been well looked after. Find a nice one and you wont be disappointed either.

 

[Monkeylegend]

I have an '04 350 and apart from a new starter battery has so far been problem free.

Apart from what's already been mentioned the other things to be aware of are the SBC pump operating the brakes. This has a finite life based on number of operations but can sometimes be reset. Having said that a replacement is not wallet breaking in the grand scheme of things.

They are also very sensitive to small drops in auxiliary battery voltage
and will throw up warning messages which can be quite alarming at first.

These will clear when the battery is fully charged again, normally a 20 min run will sort this. I would recommend a trickle charger for the auxiliary battery if not being used for a few days especially in cold weather. I have had no issues since using one.

Find a good one and you will be well rewarded.

 

[Monkeylegend]

I have an '04 350 and apart from a new starter battery has so far been problem free.

Apart from what's already been mentioned the other things to be aware of are the SBC pump operating the brakes. This has a finite life based on number of operations but can sometimes be reset. Having said that a replacement is not wallet breaking in the grand scheme of things.

They are also very sensitive to small drops in auxiliary battery voltage
and will throw up warning messages which can be quite alarming at first.

These will clear when the battery is fully charged again, normally a 20 min run will sort this. I would recommend a trickle charger for the auxiliary battery if not being used for a few days especially in cold weather. I have had no issues since using one.

Find a good one and you will be well rewarded.

I have just checked the date of the original post, seems like any recent advice might be a bit late

 

[Philti]

SL 350 Rear Drains

Hi iv got 03 350 3.7 the engine been fine had change thermostate that was easy to do. Had own the car a year now. Fuel not too bad can get 25mpg if you give beans and driving slow. 5 speed gear box is nice, make sure oil level is right you get probelms. Make sure rear drains are clear on the boot. They do take alot too maintain, got trans oil dipstick and engine oil. The car always put smile on your face

Just bought a 2006 model for the wife and have a feeling the rear drains may need cleaning out. Can you offer any advice?

 

[Monkeylegend]

Just bought a 2006 model for the wife and have a feeling the rear drains may need cleaning out. Can you offer any advice?

The drain holes are at the base of the rear window either side where the rubber seals sit under the pointed ends of the boot lid. They are partially obscured by the seals so you need to dig around a bit to find them.

If you follow the natural drain path from the rear windscreen to the base of the screen at this point you will find them. They can get clogged with debris running down the rear windscreen.

HTH.