Recommendation for an in-line fuel filter

[Carlos]

Hi guys,

First, a little background: I was working on the fuel system on a classic car I own, a Mercedes-Benz 1962 180c (W120 chassis). I removed the fuel filter housing in order to clean it (the car has been sitting for several years). The filter housing is made of aluminum. It took a considerable amount of wrenching to unscrew it from the fuel inlet pipe side. I did the right way, using two wrenches -an open end to hold steady and a flare wrench to loosen the nut at the fuel pipe fitting. After cleaning it, I went to screw it back on to the inlet fuel pipe but the male threads at the inlet fitting wouldn’t get started on the female threads of the filter housing. I tried everything to get it to screw back on to the inlet fuel pipe, putting a bit of marvel oil on all threads, pushing it one with considerable force – nothing has worked.

I figure the filter housing got out of round when I wrenched it hard taking it off the inlet pipe, siince the housing is made of aluminum.

To make a long story short, I’ve decided to go with a new, modern-type of inline fuel filter, but I’m not sure if anyone can point me to one that would fit this particular fitting at the fuel pipe (see pic below). The thread pitch (metric) of the male threads on the inlet pipe is 1.5 MM. I measured the I.D. of the female threads of the filter housing and they are 12 MM.

I looked at Summit racing web site but all of the inline fuel filters I see there have different ends (full barbs, etc.) and they pipe measurements are all in SAE not metric. I just don’t know too many other sites to check out since my skills are at more of an enthusiast /beginner level than an experienced mechanic level.

I appreciate greatly any help and advice you can give.

Thanks in advance,

Carlos

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Topic

[Cameron]

If you are in the USA, you can get a replacement item through MB Classic in Irvine CA.

https://www.mercedes-benz.com/en/mercedes-benz/classic/classic-service-parts/mercedes-benz-classic-world-wide/

[Mike]

Well, with steel threading into aluminum, corrosion might be an issue. In your first photo, it looks like there’s corrosion in the fitting’s threads. (White residue.)

See if you can clean up the external and internal threads with a brass-bristle “toothbrush”. Something like a dental pick might help when chasing the internal threads, and a bit of penetrating oil might help loosen the deposits. Also, check to see if the starter threads on the nipple are chewed up a bit. They can be rehabilitated with a small triangular file if needed. If you have a tap and die kit with the right thread chasers, you can restore both the internal and external threads easily.

When assembling, try sliding the threaded nipple backwards along the line, and pushing the “naked” fuel line into the fitting to seat the flare. Then slide the nipple up and begin hand-threading lightly. You may have to rock the fuel line around a bit to get everything squared up and concentric. Don’t depend on the threads themselves to pull everything into alignment. If the fitting goes in even slightly cocked, it will more than likely cross thread into the aluminum. A delicate touch is required.

[EricTheCarGuy]

I’m going to assume it’s a carbureted set up. If that’s the case, you can cut the fittings off and just run rubber fuel line between the filter and the metal lines. There are plenty of off the shelf fuel filters that will fit rubber lines. It would also make changing it in the future easier and more universal. You can even get clear filters so you can see the fuel passing through them. They’re the ones I often use for that very reason. If it’s carbureted it’s low pressure and likely wouldn’t leak with just hose clamps.

[Carlos]

cam0888,
Not a bad idea at all. I actually have heard of MB Classic. I guess what initially set me down the path of getting a modern replacement instead of an OEM part, or a high-quality repro of the OEM part, is the pricing on this particular part. I did search several suppliers’ online catalogs, but this part is appears to be always out of stock. The ones I’ve seen on Ebay are sold as is (not a problem really) but are also pretty pricey.

I will neverthless will contact the MB Classic Center in Irvine for exact pricing on units. Maybe they have NOS.

Thanks!

C

[Carlos]

Evil-i,

Yes, I kept an eye our for any corrosion, but thankfully, I did not find any at all when I removed the part. The white residue you mentioned I think must be an effect of how the photo came out when I took it with the flash. The car has been kept in a dry garage during its life and thankfully it had very little corrosion in the tank when I inspected it and the gas I removed.

I did clean up both the male threads of the pipe and the female threads of the fitting. I used a brass bristle brush as well as a regular toothbrush. When I cleaned up the “nipple”, I took care not to damage the threads and only hand washed and soaked it a bit in 100% pure lemon oil, which worked a treat to get it really clean. I was tempted to take it to get it beaded, but decided against it since it’s aluminium.

The “nipple” threads are not chewed up.

“When assembling, try sliding the threaded nipple backwards along the line, and pushing the “naked” fuel line into the fitting to seat the flare. Then slide the nipple up and begin hand-threading lightly.”
That’s an interesting idea. I’d have to jack it up again and disconnect the fuel pipe at some point to do that. Hmmm. might be worth a try.

Thanks!

C

[Carlos]

Eric,

Excellent suggestion. Thanks! I figure I could just use my angle grinder with a metal cut-off wheel to make the cut. Then just deburr it with a reamer.

Yes, it’s carubureted. And yeah, low pressure I guess. My only concern would be a vacuum leak or loss of prime to the fuel pump (?). Would that even be concern here in this scenario? I guess I could use some Hylomar just to be safe at the hose and pipe connection. Not sure.

Thanks to everyone for your help!

I’ll report back with what I ended up doing.

C

[Carlos]

I’m leaning towards just cutting the fittings off.

Just wanted to know what would be your recommendation for cutting the pipe – a steel pipe cutter like the kind used in plumbing, or an angle grinder? I don’t have a pipe cutter but I think it might be worth getting/borrowing one if it makes a cleaner cut, if that even makes a diffierence.

All help greatly appreciated,

Carlos

[Mike]

I don’t know what the collector value of your car is, but ’62 was the last year of the “pontoon” body style. With that in mind, I’d be inclined to keep things as original as possible.

[Carlos]

[quote=”Evil-i” post=169560]I don’t know what the collector value of your car is, but ’62 was the last year of the “pontoon” body style. With that in mind, I’d be inclined to keep things as original as possible.[/quote]

Absolutely correct. I haven’t made my final decision yet because that is precisely what is coursing through my mind right now. I’d really like to keep the car as original as possible, because that is what preserves the collector value of the car for these classic Pontons. Although the 180c 120 chassis does not command nearly as high a market prices as say, the 300D Adenauer ($100k +), I still would not like to cause it to be worth less. The W120 chassis Pontons if well-restored, generally go for between $7k up to $20k. Most good examples sell for around 8k -10k.

I called the Classic Center today @ 10:30 am California time and left a voice mail. Hopefully, they’ll return the call promptly with some info on this part.

[Author]

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