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**Ocracoke** · 23-03-17, 12:03 PM

Welcome to the forum, nice to see another localish member!

The MHD is a pretty mixed bag. I know of drivers who have never had an issue with theirs before but conversely, I have also heard of the horror stories as well. I think Smart themselves have tried to rectify this at least 3 or 4 times now (the latest change is a different pulley wheel) but the fact is that if that belt goes, that is it. At the same time, Smart removed the water temperature gauge as well from the LCD display in the speedometer so you can't tell if there is a problem until it overheats.

I'd rather go and find a 84bhp turbo (which is not a MHD and I know there is at least one in the Merseyside area for sale) or find a older (2007-mid 2008 ish) 61/71bhp which is not a MHD.

**Thrumbleux** · 23-03-17, 05:06 PM

Should I avoid the MHD model?

Yes.

**tolsen** · 23-03-17, 06:53 PM

I suggest you study what Evilution is saying about the MHD and its belt failures.

MHD Belt Failure | Evilution

http://www.evilution.co.uk/index.php?menu=info&mod=886

**137699** · 24-03-17, 09:13 AM

Originally posted by thrumbleux View Post

should i avoid the mhd model?

yes.

^^^^ this ^^^^

**Wesley Smart** · 24-03-17, 10:35 AM

Thank you guys for your reply! Even buying a used car has its risks and now you gotta have this to take into consideration! Excuse me for being a Smart newbie, why does this problem only affect the MHD models and not others? Is it because the design of the engine or what?

Ocracoke - Thank you for your comment! I am planning to purchase a 2nd generation of the Fortwo. I have never bought a used vehicle before and there are a lot of scams on eBay. I have been learning more about the car by watching YouTube videos and hopefully obtaining more invaluable information from you all SMART people here. I guess I just have to wait until my dream Smart Fortwo come along......

tolsen - Thank you for sharing the link! I had already found this link before I made this post but hadn't read it properly. I think I will avoid the MHD range having read the article thoroughly. Who wouldn't want to own a car free from trouble? I will be more than happy to choose a different model from the range. Is a Diesel a good choice although I won't be doing so much motorway driving?

**Thrumbleux** · 24-03-17, 10:55 AM

MHD was rushed into production and poorly engineered. Combined alternator and starter motor with a belt to the crankshaft, the belt and its mechanisms aren't strong enough for the forces involved in starting the engine. Hence the failures.

Later higher powered diesels can be problematic - esp on short trips. Earlier ones a safer bet.

**Ocracoke** · 24-03-17, 10:56 AM

Excuse me for being a Smart newbie, why does this problem only affect the MHD models and not others? Is it because the design of the engine or what?

It is down to the design of the engine where there is too much tension on the belt and ultimately snaps because of this.

Is a Diesel a good choice although I won't be doing so much motorway driving?

CDis were generally known to be trouble free pre 2009 (where they were 45bhp) but after then (where they were 54bhp), the inclusion of a DPF meant that unless you did do regular motorway driving, it would block up and cause plenty of issues on its own. As I noted in my last post, a 84bhp petrol or a non MHD 61 or 71bhp are generally trouble free so if I was going to get a 451, that is what I would aim for.

**Wesley Smart** · 24-03-17, 01:38 PM

Thank you guys!! Has anyone had the misfortune of a V-belt snapping??!

**Thrumbleux** · 24-03-17, 02:16 PM

Originally posted by Wesley Smart View Post

Thank you guys!! Has anyone had the misfortune of a V-belt snapping??!

Not me (as I have a 450) but plenty horror stories out there when the belt snapped and the driver missed the high temperature warning and cooked the engine.
What appears to happen is that the tensioning provision cannot cope with the forces (it also has forces in both directions - which is unusual for a belt system) and yields which then puts the belt out of alignment and as it is a flat multi-groove (not simple V) belt, failure of the belt follows swiftly.

Consider an MHD only if: you buy it cheaply; you are prepared to regularly check the belt alignment and replace when there is any doubt (that could include the pulley(s)); are prepared to risk a lost engine (if it overheats and you miss the warning); are prepared to accept a low price on resale. Otherwise, swerve.

Pick of the 451 range is the 84 turbo. Very little goes wrong with them and the 84hp provides a spirited drive.

**Ocracoke** · 24-03-17, 02:26 PM

I have had a 450 that the V belt snap on it whilst on the A55 doing 70mph and only knew it was overheating when I just happened to look down at the speedometer to see the water temperature go through the ceiling (why the 451 had the water temperature gauge removed is beyond me).

As the starter motor is separate to the alternator in a 450, I could just about limp into Holywell after stopping over at the services Caerwys to let it cool down. The MHD, as Thrumbleux says, has a combined starter/alternator so if it breaks, you also lose the ability to start the car which can strand you anywhere.

**tolsen** · 25-03-17, 08:07 AM

All 451 Smarts and later models are cars to avoid in my humble opinion. The 451 is poorly engineered and hopeless to work on. Later models are not Smarts but Renaults so buy a Renault instead if that is what you want. The only good Smarts are the 450 diesel and 450 Brabus.

**Wesley Smart** · 25-03-17, 08:28 AM

Thank you thank you! So how can you distinguish a turbo and a non-turbo? I have seen both being advertised and their performances are very similar so what is the turbo for??

**Thrumbleux** · 25-03-17, 09:01 AM

Originally posted by Wesley Smart View Post

so what is the turbo for??

Raising the output from 71 to 84hp. Identifiable by those numbers.

**Wesley Smart** · 25-03-17, 09:15 AM

I do apologise! I meant I have seen 84hp Smarts being advertised but there's no mention of turbo, so are all 84hp Smart cars turbos? Thank you!!

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Should I avoid the MHD model?

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