Greenhorn's easy ECU Hose Test

As part of the effort to bring the '97 Passat back from the brink, I've got the intake system pretty well squared away. I also replaced the N75 solenoid, replaced the fuel filter, primed it with Diesel Kleen (silver bottle) and eliminated that Mr. Gasket fuel pump that was between the filter and the IP. I have not started the car yet.

Ive been reading about replacing the vacuum hoses, and it seems like a good idea, but wanted to run my idea past you guys regarding the infamous little hose in the ECU. Instead of pulling it apart to check, why not just apply some vacuum to the hose coming out of the unit. If it holds, then maybe one is better of leaving that one alone since the ECU is easily damaged. The rest of the lines can easily be replaced....

If your boost gauge is tee'd off the ECU line, then you should have a good idea of whether the ECU hose is holding air by driving the car unless the leak is really small.

Yblocker said:

A Instead of pulling it apart to check, why not just apply some vacuum to the hose coming out of the unit. If it holds, then maybe one is better of leaving that one alone since the ECU is easily damaged. The rest of the lines can easily be replaced....

Click to expand...

This is a pressure hose - since the MAP is in the ecu case, and the hose goes to the boost hose.

So, use a pump with good gauge, see if it holds at 12 lbs.

However, the ecu isn't all that fragile. I've taken mine out 2-3 times for various reasons (changing hose, changing chips, changing chips back). It's no big deal. The hose will need to be replaced soon, so why not now? It is rotting away as we speak.

Yblocker said:

As part of the effort to bring the '97 Passat back from the brink, I've got the intake system pretty well squared away. I also replaced the N75 solenoid, replaced the fuel filter, primed it with Diesel Kleen (silver bottle) and eliminated that Mr. Gasket fuel pump that was between the filter and the IP. I have not started the car yet.

Ive been reading about replacing the vacuum hoses, and it seems like a good idea, but wanted to run my idea past you guys regarding the infamous little hose in the ECU. Instead of pulling it apart to check, why not just apply some vacuum to the hose coming out of the unit. If it holds, then maybe one is better of leaving that one alone since the ECU is easily damaged. The rest of the lines can easily be replaced....

Click to expand...

That is a very good idea instead of opening up the ECU and possibly f**king it up (like I did) . Don't use vacuum, use pressure. You can easily rig a test setup with a plastic tee, a boost gauge, a shrader valve, vacuum tubings and a bicycle pump. Pump it up to 10 psi. If it holds pressure, it is not leaking. No and, ifs or butts about it!

Why is the hose in the ECU rotting away? It is in a sealed housing well protected from the elements. Is it made from chewing gum? When I took mine apart, my hose looked perfectly fine. But I took it off from the advice given here like there is some magic behind it and promptly broke the frickin nipple off the MAP sensor.

A good boost spike from a tune can split the hose. I think mine is silicone now.

dieseljunkie said:

Why is the hose in the ECU rotting away? It is in a sealed housing well protected from the elements. Is it made from chewing gum? When I took mine apart, my hose looked perfectly fine. But I took it off from the advice given here like there is some magic behind it and promptly broke the frickin nipple off the MAP sensor.

Click to expand...

It does age. It just gets brittle and small cracks are developed. Care must be taken in removing it - the slicing of the edge of it takes the pressure off of the nipple.

It doesn't take much longer to replace it than it will to rig up the testing device.

OK well I replaced all the vacuum hoses today except for the one in the ECU and the one from the ECU to the nipple on the intake. Getting the hoses off the nipples on the turbo was pretty difficult with the factory clamps. No clamps went back on... I hope a snug fit with the new hoses will do.

Now of course in order to leave no stone unturned, I'll have to replace those ECU hoses too I suppose. I'll pick up a razor blade tomorrow to slice them.

YB--I opened up my ECU on the advice of the forum here and the hose was fine. I considered replacing it, but honestly, sometimes replacing things brings risks to breaking other stuff, so I left it alone. Yes, I know how to remove vac lines with a razor blade, did that on all the boost lines in my car. And yes, I know it is an old hose, but like mentioned previously, it is sealed up in a protected spot.

The ECU is also pretty difficult, though not impossible, to remove. There is room for error and the possibility of breaking something. Seeing as my car is running correctly I choose NOT to replace this hose rather than risk damaging the ECU.

Oh, and the factory clamps--I just cut them off with tin snips. PITA. I have used small worm-gear clamps to replace just not over-tightened.

Yblocker said:

OK well I replaced all the vacuum hoses today except for the one in the ECU and the one from the ECU to the nipple on the intake. Getting the hoses off the nipples on the turbo was pretty difficult with the factory clamps. No clamps went back on... I hope a snug fit with the new hoses will do.

Now of course in order to leave no stone unturned, I'll have to replace those ECU hoses too I suppose. I'll pick up a razor blade tomorrow to slice them.

Click to expand...

I may just replace the longer one from the ecu to the intake nipple and call it good. The one end on the intake is worn, so that one should be replaced.

The hose inside the ECU is very easy to change. I am a newbie and I did it. I brought my TDI with the code, and right away after searching the forums I took out the ECU and sure enough the hose was really soft and there was a hole in it. I carefully pulled it off and replaced it with some extra hard plastic like hose from a boost gauge kit I had. I guarantee that I will never see that CEL code again on this car.

http://www.myturbodiesel.com/1000q/a3b4/ecu-hose-chip-tdi-65535.htm

I didn't replace because: A. I didn't have a code. and B. The old hose was working fine. Best not to create problems by finding problems that don't exist yet. Honestly, YB, I'd recommend just the outer hoses especially if your car has seen some garage use or moderate weather. I'm here in the Midwest with weather extremes, but my car sees about 50% garage use. The original ECU hose was fine, and my car has no code or problems at this point. Runs great with incredible power.

Be very careful if you are going to try cutting the band clamps with snips such that you don't torque and twist the plastic nipples off. If the hose ends are soft from age, you may be able to just twist and pull the hose off with the clamp still on. Squirt some soap on it for lube to help it come off. If it doesn't feel like it wants to come off don't force it- get the clamp off first. If you study how the clamp works, you can pop the locking claws with a small sharpened flat blade screwdriver very easily so you do not have to cut them, which is kinda brute force and risky IMO.

I didn't replace a single vaccuum or pressure hose on mine. The ends were soft. I pulled them off one by one, cut 1/2" off the ends and put them right back on. All my hoses pressure and vacuum tested fine. Why replace things if they are not broke?

Stealth TDI said:

A good boost spike from a tune can split the hose. I think mine is silicone now.

Click to expand...

It is made from bubble gum!

When I bought my car way back when the CEL was on for a faulty computer.

Knocked $2k off the price of the car.

Drove home and opened up the ECU and the hose "looked" ok, however I replaced it and the faulty computer has been working for the last 7 years.

The factory hoses in the ECU and to the ECU deteriorate because the oily vapors from the upper boost pipe forced into the hose. The rubber falls apart from the inside out.

Just replace the hose in the ECU and be done with it. I guarantee it's fragile after all these years.

I like silicone hose, but good 1/8th inch vacuum line will do it.

Well, I just replaced all the hoses except the internal one in the ECU. Tha fact is none were leaking and I would expect the external ones to leak first. The ECU is sealed from the elements.

soup **** said:

The ECU is sealed from the elements.

Click to expand...

Sure it is. Except for the oily boost vapors that attack the hose from the INSIDE. Change it.