Ant Tips for Tandem Pump Replacement on a BEW Engine?

Any Tips for Tandem Pump Replacement on a BEW Engine?

This weekend I'm replacing my tandem pump (the one on the Jetta is weeping a little diesel on its underside). May be just the mounting gasket, but I want to be sure I fix it.

My replacement tandem pump arrived today (from 1stvwparts.com). Total, including shipping, was $262 (my local VW dealer wanted $370 plus tax).

Zeb (at 1stVW) told me the pump number just superceded to 038-145-209-Q and that is what I got. Its a Bosch pump with the audi/VW logo on it. It came in a sealed plastic bag, the pump wrapped in brown paper, and saturated in what smells like diesel fuel. It appears the mounting gasket/thin metal plate is attached to the pump. UPS must have thrown the box around, because there was a small hole in it where one of the metal fuel line nipples poked a hole through the box, but the pump appears to be OK. It would have been nice if the fuel line nipples were capped. The nipple for the vacuum line (to the brake booster) was capped. I just need to make sure no trash got into the fuel line nipple on the pump.

The replacement looks straight forward from reading my Bentley. Suction out the fuel from the return line at the fuel filter connection, disconnect all lines, unbolt pump, install new pump with gasket and torque bolds to spec., attach lines, and prime with suction pump. I plan on using my Pela oil extractor to suction the fuel loop dry before removing the tandem pump (by duct taping the Pela line to the fuel return line--Bentley says to use a hand vacuum pump). I'll prime the new pump the same way.

Bentley does not mention this, but it looks a whole lot easier if I remove the air filter box first.

Anything else I need to know?

Thanks.

--Nate

Replaced my pump too cause it leaked fuel. The fuel leaks right onto th small coolant line under the pump causing it to swel up and soften the rubber. Take a close look at your hose it probably got it too.

Thanks. I'll check that.

--Nate

I wouldn't bother with the vacuum pump. The lift pump primed the lines sufficiently when I changed my tandem pump. Take off the return line somewhere and stick it into a jar. Cycle the ignition and when you see fuel you're good to go (reconnect the return line, of course!).

You'll probably need a bit of a first crank to push out the air in the lines in the head.

I wonder if there is a way to run the old pump dry before removal. Possibly by unplugging the lift pump and disconnecting the hose that feeds the tandem pump from the FF and then running the engine. Could this do any harm?

Replaced the tandem pump today. The trickiest part was getting to the lower-most bolt. The coolant flange was in front of it. The Bentley manual does not say to remove the coolant flange, but depicts which pump bolts to loosen without the coolant flange mounted. I simply used an old style "L" allen wrench to get to it and I got enough of a bite to get the bolt out. No way I could use a torque wrench with a 3/8 drive 5 mm allen to tighten it. I just got it good and tight with my "L" allen wrench. I also broke one of those nasty little springy steel fuel line clamps and dropped another one on my skid plate. I had some spare small worm-style hose clamps and used those.

It was tricky getting the new pump to engage the camshaft slot, but putting the car in gear and pushing it backwards a foot got the pump tangs to engage the camshaft.

I also could not suck out the fuel loop very well using my Pela oil extractor. I got most of it out, but it was slow going. Sucking fuel into the fuel loop was slow too, and I cycled the key several times to cycle the lift pump to help the Pela. After the pump was replaced I still had to crank the engine about 15 seconds to get it started.

It appears the original fuel leak was at the mounting gasket, so I may not have needed to replace the pump. One oddity though is that the engine fires up instantly when I crank it when warm, whereas before a second or two was needed to get it to light off. Maybe the new pump holds pressure better.

The vacuum nipple on the new pump is rigid (cast with the pump or screwed in). On the old pump it was pressed in and swiveled and was a little loose and may have been leaking vacuum.

--Nate

I disassembled the old Luk tandem pump. It had 127,000 miles on it. It was relatively unworn inside and was quite rhobust and well made. There is an oil feed hole, where the pump gets oil from a galley in the head to lubricate the vacuum pump (the fuel feed pump is diesel fuel lubed). The vacuum pump exhausts into the cylinder head (where there must be a passage to the block and oil pan, I guess). The oil returns at that point too. I now see how an internal seal failure of the fuel pump can cause diesel fuel to get into the engine oil. There is a double lip seal sealing the common main shaft from the vacuum pump and fuel pumps (the vacuum pump sits next to the head and the fuel pump is mounted on the other side of the vacuum pump. They share a common drive shaft). If this seal fails, diesel fuel under pressure will flow into the vacuum pump cavity and will be exhausted into the cylinder head port and will drain into the oil pan. There will be no external leaks at all if this happens. You will only know from high oil level that spells of diesel fuel.

The mainshaft was very snug and there were two slight wear rings where the shaft ran on its seal.

The fuel pump had a microscreen in it to keep any junk from making its way to the injectors. The screen in the old pump was completely clean. No need to worry about the slight bit of paper fibers that were inside of the new pump's fuel in nipple, although I flushed them out with WD 40 and blew that out with Dust Off)

I doubt if you can get reubuld parts for the pump and it appears it could last well into the 200,000 - 250,000 mile range. For $270, you might as well replace it.

I do believe the metal seal plate (available separately for about $10) was the source of my external slow fuel leak from the tandem pump. This seals the pump to the cylinder head. If I get another leak, I will replace this seal next time. Before I removed the pump I just did not know and I did not want to take chances.

--Nate

Thank for the write up, I think mine is leaking too. The bottom of the cylinder head is wet with something and it goes around the entire left side of the head. It is not a large leak, just enough to make a wet area on the head. I can't seem to find where it is coming from though. I am assuming it must be coming from the tandem pump because thats where these engines are prone to leak from.

Should I just buy $10 gasket and try that or should I buy the entire pump?

Nate, does this new pump cure your smokey start-ups, or am I confusing you with another member?

JB05 said:

Nate, does this new pump cure your smokey start-ups, or am I confusing you with another member?

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I have smokey start-ups only when below 40 degrees. Its the glow-plug system and possibly injectors. Early PDs suffered this fate and I still have the original GPs and coding. I did not have the recall performed because I did not want to lose my chip tune and don't trust the dealer.

--Nate

turbocharged798 said:

Thank for the write up, I think mine is leaking too. The bottom of the cylinder head is wet with something and it goes around the entire left side of the head. It is not a large leak, just enough to make a wet area on the head. I can't seem to find where it is coming from though. I am assuming it must be coming from the tandem pump because thats where these engines are prone to leak from.

Should I just buy $10 gasket and try that or should I buy the entire pump?

Click to expand...

Take your right hand and shove your fingers under the tandem pump, wiping the pump with your fingers. Try to get the lower-most area where the lower fuel line exits the pump. If leaking, you will get a coating of diesel fuel on your hand. It will smell liek diesel too. That lower-most point is where the fuel feed and return holes into the cylinder head are. The lower smaller pump bolts apply pressure to seal the pump to the head over those two holes. That most likely is where the leak is.

The only other potential external fuel leak point is its pump top cover. If it leaks there and tightening the cover bolts/screws do not help, the pump must be replaced. A gasket seals that, but is not available.

There could be an oil leak point too (upper to mid section of the pump), because the pump gasket seals the camshaft drive hole in the head, vacuum pump exhaust hole into the head, and the little oil hole from the head that lubricates the vacuum pump part.

I would just try replacing the gasket. It is a thin metal plate with rubberized stuff in critical sealing areas. It seals the whole pump to the head. Its about $10. Part number is 038 145 215 (from the stamped number on the old gasket). Just clean away all dirt and oil before removing the old pump. You do not want ANY dirt getting into the fuel galley in the head.

--Nate

Thanks, it looks like oil that is leaking from the gasket that seals it to the head. I am leaning toward just putting on a new gasket and see what happens.

My BEW starts pretty smokey/rough too. I think its just the software these cars came with from the factory.

I have another question. Why did you have to move the car/turn the engine to align the cam shaft with the new pump? Is the pump that difficult to turn by hand? I have never dealt with or seen the inside of a tandem pump.

The pump is real easy to turn, but once its started in the hole in the cylinder head, you can only fine tune its alignment by turning the camshaft slightly to engage the tangs and slot in the cam. Turning the 19 mm 12-point crankshaft bolt would work too, in addition to moving the car in gear.

When installing the pump, you first eyeball the camshaft slot and position the pump shaft so as to align its engagement tangs with the slot in the camshaft the best you can, but the toterances are so tight it is hard to get it right on and the pump won't push home into the side of the cylinder head. While it is partly inserted, you wiggle the engine back and forth a few degrees so the the pump can engage the camshaft. Ideally, it would greatly help to have two people: One to move the engine slightly CC and CCW, while the other pushes the pump into the side of the cylinder head. Once it engages, the pump moves the final quarter inch to be flush with the cylinder head.

--Nate

Hi Guys thanks for the tips - can you please advise what the recommended torque settings are for the mounting bolts.

Thanks,

Paul

Does anyone know the thread pattern on the PD tandem pump allen head bolts? I changed mine about a year ago, but in the process stripped one of the treads out.

I'm getting leaking again and I'd like to get a helicoil or similar insert to replace the damaged threads in the block. I would change the gasket at the same time.

-Eric

tq spec

What are the tq spec for the bolts on the tandom pump?

Thanks
Robert

I found these values in another thread:

What I didn't expect, the two larger screws I had a torque wrench (20 N/M= 14.7 ft/lb) but not for the smaller (10 N/M = 7.4 ft/lb)....

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Can someone else please confirm these are correct?

This thread has been so helpful in diagnosing a persistent leak. I first replaced just the gasket but that didn't seem to solve it (or perhaps I missed something), and am now going to try the pump itself this week as the head is still wet all around that side. I've read on myturbodiesel.com that it might also be a good idea to add a little silicone around the mating surface of the pump and camshaft end. This would be where the pump slots in, I'm guessing.

Anybody else done that? And are those torque spec confirmed? Though wouldn't 7.4 ft-lbs be too low for an accurate reading and inch-lbs be a better application?

Didn't add any sealants to the new gasket when I did mine. I just bolted it on. I tried simply replacing the gasket between the old pump and the head, that didn't stop my drip, so new pump was the ultimate cure. Looked under the hood the other day, nice and dry down at the hose elbow below.

Now I did manage to break my coolant outlet flange on the side of the head when I did my pump... That was fun!!

Just to add info to this thread, I replaced my tandem pump (215k, original LUK unit) and there was copious oil, some diesel and dirt caked all around the bottom side. The vacuum fitting/nipple on mine was also loose, and there was oil in the vacuum line, too. gross! It was very hard to see because most of the leaks were in the back right corner of the pump, which is almost entirely hidden by the big coolant flange directly below, and a coolant hose directly behind. Very hard to get a finger in there to find the leak.

Removing the pump was made less messy by using brake and fuel line clamps - one on the supply side kept the fuel rail full, which helped (a little) in starting the car after job was done. That and a small plastic container to drain the input/output nipple of the pump, a lot of rags. Still smelled like diesel, no getting around that.

When replacing with a new pump, it's important to clean that mating surface properly. There were some cooked oil sludge/gunk that was making a trail to leak behind the gasket in my case. Spray brake cleaner onto a shop towel that won't shed fibers, and slowly remove. Try not to scrape that aluminum!

To help with aligning the camshaft and pump drive, try to match the orientation of the old pump with your new one and wiggle it into place. Easier than trying to move the car in gear while pushing the pump on.

I also recommend using new bolts, part #: N0903872. They have redesigned heads, which are M10 triple square (big top bolts) and t30 torx (small bolts), which replace the 6mm and 5mm bolts originally spec'ed. My lowest bolt head was almost entirely stripped - that a was a stressful moment to start the repair! Really glad I had new ones to replace with and didn't worry about getting grip. I found no loc-tite on the original bolts, so didn't put any on the new ones.

Using an inch-pound torque wrench on the lower bolts (to get to 10 NM) was very helpful as well, as my regular wrench couldn't read below 20 NM. Tighten in a star pattern, slowly increasing force - I went around 3 times to get to the proper spec, making sure the pump was perfectly seated in the process.

Hope that helps the next backyard mechanic who replaces their tandem pump!

Great thread! Thanks for all the excellent information!

vernatp said:

Replaced my pump too cause it leaked fuel. The fuel leaks right onto th small coolant line under the pump causing it to swel up and soften the rubber. Take a close look at your hose it probably got it too.

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My hose went like that last year, was a $60.00 hose from the stealer , was an emergency and needed car back on road immediately. Was a complete BS job for me an Noob DIY'er

My pump is now leaking also. Glad I found this very helpful thread, despite it being a few years old.

I too am glad I found this post. I've had hard starting issues after the car sits overnight..... I first noticed the lift pump was not working at all, so I replaced it. Still hard starting after sitting. Once I get it running, after about 15 seconds it runs perfectly, and will start up just fine in any temp if it only sits a few hours.
I also wanted to check the glow plugs, but the wiring harness disintegrated in my hands when I touched it.... So I installed new glow plugs and wiring harness...... Still hard starting after sitting overnight. It really seemed to me like it was a loss of fuel pressure after sitting overnight. I didn't initially see any fuel leaks in the tandem pump. But I removed the EGR Valve to clean it, since it had never been cleaned in 421,000 miles and dropped a bolt onto the skid plate.... Got underneath the car and found what looked like some sort of leak on the drivers side of the engine..... Took a much closer look at the tandem pump and could smell diesel fuel.... New tandem pump on order and I'm fairly confident it will cure the hard starting after sitting overnight.

New Bosch pump installed, and no more external or internal leaks so far. It would help to remove the battery and tray to access the lower 5mm allen bolts.

What a life saver this thread has been. I have been researching this topic for hours. I had my tandem pump gasket replaced 5 days ago by an independant VW shop. To my demise, the leak persisted the next few days. I have quite the suspicison that my tandem pump needed to be replaced, and this thread has absoloutely confirmed it. My car has 330,000km on it, and I believe it is a factory pump.

Thanks all, going all the way back to 2011. I hope you are all doing fantastic and your dreams all have came true. TDICLUB 4 Life <3

Thank you guys so much for the info but there's still some things I'm confused about. Do you have to remove the coolant housing to get to that bottom bolt and would there be any problem with the new air in the housing? (Ofc you'd add more coolant I just don't know if that gap will effect anything like the air in the fuel lines will). Again, thanks everyone for the help!