Installing oil pressure gauge -- sludge problem

Arthur Marks aamarks at
Tue Jul 19 20:04:53 EDT 2005

Tony, thanks for the info. I had just completed the install so I'll give the details of what I did in case anyone can use the info and in case anyone can point out stupid errors.

This was done to a B6 A4 1.8T Q

Overall it wasn't too difficult but it would help if you were a contortionist with nimble hands.

I went with a cheap mech gauge with nylon tubing, thinking that I could upgrade later if necessary. I figured there was no reason to look for copper based on the warnings I had heard about vibrations eventually cracking it. I already had 6' of 5/8" i.d. windshield washer hose around the house so I stuffed the nylon hose in that. It kinked a little when I tried to push too much at once. Pushing in no more than 3/4" at a time worked well. Once it was in the rubber hose it behaved well during the install.

To gain access for the install I removed the plastic engine cover, the weather stripping that holds the long plastic cover over the rear of the engine bay, and I pushed the coolant reservoir out of the way. Only one screw to remove the reservoir, but the plastic prongs that go into the metal tabs on the firewall were hard to work free (pulled up and towards the front on the reservoir).

I threaded the hose through a rubber grommet on the inner firewall located just to the right (looking from the front) of the round brake servo unit. I had pulled the grommet to cut the hole for the hose (keep it small for a tight fit) and getting it back in was one of times it would have helped to be a contortionist. In the cockpit this grommet is above the brake pedal and above the black plastic where the users manual is stored.

I wasn't sure if this was going to be a permanent install so to get through the outer firewall I just routed the hose between short section of the guide for the weather stripping and a rectangular rubber grommet that had two metal hoses passing through it.

I installed the sender (not sure if you call a mechanical one that) in place of a plug that was located inline with and opposite from the oil filter, so that I wouldn't have to mess with the oil pressure warning light. This is the operation befitting a contortionist. I used ratchet extensions and a swivel to get the plug out and put in the sender. Then I used a small crescent wrench to fasten the hose with its compression fitting. After dropping wrenches and having to fish them out of the belly pan it finally dawned on me that I could tie a string to the wrench.

I wish I had known that the sender had a tapered pipe thread. It would have spared me from an unnecessary trip to the auto parts store thinking it had either defective or incompatible threads. It didn't take much tightening to make it leak proof and I don't think you'd want to over do it as the filter housing looks like it's made of aluminum.

Readings I got on the first test drive:
20 psi @ idle; 45 psi @ 2000 rpm 
(Bentley CD says 19 psi @ idle; 50-65 psi @ 2000 rpm). 
It gets to about 70 psi during hard acceleration.

I'm thinking the 45 is close enough. Anything to worry about? -- This car had its oil pump replaced at 25k miles and has had oil light warnings since. I'm thinking that now with the proper oil, filter and interval specs the sludge problem has been reduced to one where the sludge is gradually being cleaned up and is clogging the filter. The dealer has my next oil change interval at 2000 miles.


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