# Speed Up Your Older Merc Hymer



## wub (Mar 16, 2011)

If you have a older merc hymer with steel tank and you want some more power, try the very simple, very cheap fix of changing the in line fuel filter on top of the tank. 

I did through advice of the ex mechanic of the Turbo fitting people when i asked why my hymer felt so slugish. It was clogged solid and it was changed less than 10 months before! I felt i huge difference, but when i clogged 3 filters in 6 months, (I used the clear type, about £5 each, so i could see if it was getting blocked) i decided to drop the tank and give it a real good flush through, and loads of diesel gunk came out, i ssuppose20 years build up. 

So its cheap, its easy, and worth doing just to see. 

And any one interested in getting higher cruising speed from these merc hymers, get in touch. I changed my manual gearbox for the overdrive version, (first 2 gears are the same, last 3 gears are longer,) giving 12 to 15 miles on the top end speed, which means your engine is no longer reving its n..s off at 60MPH! I cruise along nicely at 60 to 70 MPH. 

I think some of the earlier hymer 660, 700 etc had the lower range box, and then when the overdrive box came out it was fitted to some later models, which my explain why some hymer 660 \ 700 owners cant work out what all the fuss is about when others ccomplainof very low, bearable, cruising speeds. 

Again fairly easy job for a garage as there loads of room around the gearbox, and they are around if you know what to look for.


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## funkyronster (May 1, 2005)

*New gearbox fitted today!!*

Thanks for your (and others) post about gearbox.

I just swapped my box today for the low ratio box. Paid £200 exchange unit from a very helpful Merc breaker down in Plymouth, who explained the difference.

Only had a short drive, but it's a totally different van now - can barely maintain 30mph in 5th - 4th feels like 5th used to be.....can't wait to get on the M6!

Looking for some 609 wheels .........

Didn't know there was a fuel filter on the main tank, mine must be foul! How do you get at it?

Ron


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## veevee (Nov 6, 2011)

Just changed the neoprane fuel hoses connected to the tank sender unit (these were original but the crimp clip s no longer held the hoses tight), didn't see a filter though. 

There is a strainer inside the tank on the fuel pick up pipe I believe, plus an inline pre fuel-filter filter situated on the LH side about where the engine and gearbox mate, and of course the main fuel fiter, but nothing on top of the tank.

Ours is mainly original as although 20 years old has only 68,000 kms on it, so still has most of the original yellow painted check marks all over from when it was built.

Think that good exhaust boxes are important, the construction and internal design do vary wildly. Also over time the silencing material will clog up bit by bit, that's carbon and rust particals.

Ron, have recently bought a drive belt from a French Mercedes dealer, came out at just under 34 euros which at current exchange rates makes it cheap than UK eBay for pattern belts.

Had a couple of gearbox parts bought for me in Germany by a friend, even with post these were about 25% cheaper than that quoted by Mercedes UK.

Also bought a few parts in France for our Ducato works van and they were definately cheaper than the UK. 

Maybe it's best to order parts outside of the UK and fit them / have them fitted in the UK?


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## wub (Mar 16, 2011)

Glad the gearbox worked out well, the difference is amazing is'nt it?

I was advised by my local old Merc van man, he's been working on merc trucks, van and campers for years, to take the intank stainer out of the fuel tank and throw it away, as its a real pain to get at it to see if its blocked, 

You have to drop the tank down slightly if its a long range tank, by undoing the 4 bolts holding the tank up and balancing the tank on a trolley jack, lowering down about 6 inchs, so there is enough room to lift the fuel pickup \ stainer unit out of the top of the tank. Made sure it nearly empty before you do this as it can get very messy if it slips off! 

Replace this strainer, with a clear inline filter on top of the tank, in the fuel line, where its easily seen and swapped. 

I have done this and check mine after every long trip, just to see how much dirt is in it. And if it looks clogged, its just the matter of undoing 2 x jubilee clips, and replacing it. They cost about £5 each and they are finer than the inline strainer, so keep the main fuel filter by the engine, cleaner for longer. Make sure you get one big enough, so you don't restrict the fuel flow. 

I guess your inline filter is the one by the gearbox you mentioned, but i like it on top of the tank as that is where my fold down step is, so when its down i have a clear view of the top of the tank and the filter. Might be different for other types of hymer? 

I was told that as these tanks get older the coating they had inside starts to breakdown and come off, which is why even after a good clean out of my tank, i still get quite a lot of bits in the filter. 

Talking of exhausts, they are quite a short system on the merc 410 hymers and only one silencer. So I recently went to a stainless steel exhaust specialist and had a system made up for £175. Which considering its going to last for a long long time and no more wasted time trying to find a exhaust and then a place that can get the camper in to fit it, is excellent value i thought. 

The only S\S exhaust place i could find locally was a bit of a boy \ man racer place, so i had to tell him i defiantly wanted a very quite exhaust! And large enough bore, not to restict flow, but give them their due, they did an excellent job, and made a lovely crafted exhaust system.


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