[DiabloClyde]

Just changed my PM settings. Thanks for letting me know.

 

[DiabloClyde]

Ok, so I spent a few more hours on this. The radiator tank must be removed to access the fuel filters and the sender unit, but it is a huge PITA! It is darn near impossible to get out from outside of the car reaching over and back in under the body panel, so I had to carefully climb on top of the engine headers and access the radiator overflow tank from inside the engine compartment, (channeling my inner Sudesh!). At least on my 97, the radiator overflow tank has two large tubes coming into and out of a T on the inside of the overflow tank (see third photo), inside meeting closest to the street not closest to the engine. The removal of those two lines proved very difficult because there is just not enough room for human arms and the appropriate amount of leverage to pull the tubes off because the frame member as shown in the first photo prevents pulling the radiator overflow tank toward you to expose those lines. Keep in mind the radiator must be fully drained and you will still leak residual fluid all over the place. A side note: dog training pads with plastic on one side and highly absorbent cloth on the other side, the kind you will see in hospitals for patients that are bedridden, worked wonderfully in this application and in changing the fuel filters which I will get to next. Still, I could not get either radiator hose off of the T on the hidden side of the radiator tank so I had to actually cut the radiator line from the overflow tank back to the rear radiator. On re-installation I will install a union in an accessible location there, because if my fix of the gasket for some reason is not correct and gas still leaks, I will have to do this project all over again! It would be infinitely easier to have a union in the middle of that radiator line leading rearward from the overflow tank back to the radiators in case I ever have to pull that tank out again.

 

[DiabloClyde]

Once the radiator overflow tank was removed, I had easy access to the fuel filters. I ordered new OEM filters despite my relatively low miles because while I am in there .... The shop manual recommends replacement at if I recall correctly 45,000 miles but this is not a task you want to do again and the filters in this location are only around $80 per.

A word on the fuel filters. There is enough slack to pull the fuel filters aside and get to the sender unit with out needing to replace them, but it is very tight if you leave them in place. So I had to devise a way to disconnect the fuel line and filters and leave them disconnected for a time allowing me to get to the crux of the problem: the sender gasket.

I am an overly cautious neat freak and did not want vapors or liquid gas dripping un- collected, so again note the doggy training pads underneath. Worked like a charm. That said, I found some random rubber caps and plugs in my supplies and temporarily capped off the filters so as not to leak fluid or vapors shown in the 3rd photo. This allowed me to set them aside while I spend time on the sender unit which is doubly important with a family and kids and other distractions as they have been sitting in this picture for a week already!

 

[DiabloClyde]

I have now removed the radiator tank and upper fuel filters, replaced the fuel filters, and set them aside only to then be able to have a view of the top of the sender unit. All of this time I was worried the sender unit would not be able to be removed past the frame member visible in this photo. This was a nail biter: if there was not sufficient room for removal my entire fuel tank would need to be loosened and jockeyed enough to remove the sender unit or the tank would need to be taken out completely!

Thank God there was approximately 1 mm to spare. I forgot to attach a photo of the old fuel filters where I have temporarily blocked them from potentially leaking.

Now, when I got to this point it is a matter of loosening the five lock nuts being careful first to absorb any gas, clean any debris or liquids or sand or particles sitting in this indentation where the sender unit is. It would be bad to open the sender unit hole, pull the unit out and drop a screw, bolt, sand, bits of a gasket, or other material into the tank.

 

[DiabloClyde]

Regrettably, I forgot to take photos of the sender unit being removed as I tried to work fast. no matter how you drain your tank there will always be gas and vapors present that could ruin your whole day if sparked. I used a non-electric blower to blow the vapors out of the engine compartment, opened all of my garage doors, and insured plenty of air circulation. Battery is disconnected and electrical items in the garage are disconnected. Now is not the time to take up chain smoking either. The sender unit was perfectly fine. I could hear the float freely sliding up and down the tube when I moved it, therefore I did not feel the sender unit itself needed to be replaced. That said, I have never had troubles with my gauge level providing false readings. There seemed to be no damage or problem to the sender itself, other than needing the top cleaned that was exposed to the exterior of the tank. The gasket shown in this picture appears to have no visible breakage or failure, which gives me some concern when I put the car back together. What if it wasn’t the gasket? In that case, I will be taking this part of the car apart again to diagnose the problem a second time. For this reason, one must think of being able to get back into the radiator overflow tank and area of the fuel filters again. This is being taken into consideration as I re-assemble by adding an inline union in the above mentioned radiator hose and I will not fully tighten down the fuel filters’ housing. I did tighten the five locknuts down very carefully like you would Lugnuts on a tire with equal torque going to opposite nuts and progressing back-and-forth as you go. These appear to be brass screws and aluminum gas tank and you do not want to over tighten. As an abundance of caution per my normal routine I added anti-corrosive grease to the knots and threads.

Upon reassembly, I will take it to the gas station quickly after a cold start and refuel entirely. I hope I do not need to re-siphon 26 gallons of fuel into my other two cars! If upon full refill there is no gas leakage from the sender unit area, then I fixed the problem! I will report back.

 

[mikael82]

Maybe fuel filter union was lose or sender gasket lost it tightnes.
You could fill tank up while everything is out from car.

Btw. easies place to drain coolant is from heater hose from lower radiator aluminium tube.
Also, it is worth noting coolant expansion tank is attached only from one end and it will only lift up from front side.

 

[DiabloClyde]

Not on my car. The tank has a tab that slides into a groove toward the passenger firewall while the easy bolt attachment is in rear of the tank. With no extra play in the radiator hose there was not enough wiggle
Room to remove the hoses by twisting the tank, pushing it aside, rolling it, etc just was not enough. Suggest anyone replacing radiator hose in this location to cut the new hose several inches longer than the hose coming out as just-enough is not enough.

 

[DiabloClyde]

On attaching the fuel filters and tightening down the bolts, I had two unions not want to seat properly. I carefully fired up the fuel pump by turning the key to its first position to ensure fuel pressure. And I saw drips. At this point I tightened the unions down further but I decided to add absorbent pad around each union to determine if any were leaking as seen in this picture.

Which leads me to another possible culprit: upon removal of the old fuel filters I found all four rubber O-rings, but only three of these thin metal washers shown (one is shown in my hand). these o-rings go on the metal fitting followed by their larger interior diameter washers such that when you tighten down the fuel filter the rubber expands into the inside of the washer to ensure a gas-right fitting. For some odd reason at the factory Luigi never added the fourth washer and that may have been my cause all along as I originally suspected. It likely worked just fine for these past 20 years without the washer but the O-ring started to fail and therefore leaked gas. This does not solve for the symptom of the gas leak only being noticed when the tank was full, but it could also have been leaking worse each time I turn the car on and therefore I only noticed recently. Keep in mind the fuel filters lie horizontally directly above the sender unit so any drip of leaking gas from this failing O-ring would have collected in the tank indentation for the sender unit. It’s either that or the sender unit gasket but at this point I may never know.

But amazingly I found a perfect fitting washer at my local parts store. In the Lamborghini parts manual the washer, O-ring and threaded union all are listed as one part, and I did not want to have to buy a new piece and wait for delivery.

 

[DiabloClyde]

For those of you contemplating doing the same work, absolutely replace the filters if you were to get into this area of the car as it is cumbersome enough to not want to do twice. I ordered new OEM filters which are Weber FI 02/2. As noted above, you will want to have 4 new O rings on hand which you can source at a local parts supplier. And you will want to have many absorbent towels, the ones I referenced that they use for puppy training or hospital uses work brilliantly.

That said, putting the car back together I need to ensure everything works perfectly before buttoning it all up. However I have to button the car up enough in order to make it run to the gas station to fill up the tank! So I reinstalled the radiator tank and added two inline unions, one each in the input and output tubes since they are behind the radiator tank and hard to get to. With these two unions and several inches of additional radiator hose in the lines, future removal of the expansion tank will be made much easier. This enables me to get the car to run again and test the new gasket on the sender unit to ensure it is no longer leaking and to ensure the fuel pumps are dry at their unions. If not, the entire expansion tank needs to come out again in order to get to the filters and sender unit. As they say, an ounce of prevention is worth a pound of cure.

 

[mikael82]

Good thing you found issue and notied possible leak source that is easy over look. There is fair amount pressure behind that and could cause fire, because sparkplugs are right next to it.

Filters might also be changed in some usual service, they are in "service program" and it could also be mistake made by mechanic later.

 

[Sledge4.2]

For those of you contemplating doing the same work, absolutely replace the filters if you were to get into this area of the car as it is cumbersome enough to not want to do twice. I ordered new OEM filters which are Weber FI 02/2. As noted above, you will want to have 4 new O rings on hand which you can source at a local parts supplier. And you will want to have many absorbent towels, the ones I referenced that they use for puppy training or hospital uses work brilliantly.

That said, putting the car back together I need to ensure everything works perfectly before buttoning it all up. However I have to button the car up enough in order to make it run to the gas station to fill up the tank! So I reinstalled the radiator tank and added two inline unions, one each in the input and output tubes since they are behind the radiator tank and hard to get to. With these two unions and several inches of additional radiator hose in the lines, future removal of the expansion tank will be made much easier. This enables me to get the car to run again and test the new gasket on the sender unit to ensure it is no longer leaking and to ensure the fuel pumps are dry at their unions. If not, the entire expansion tank needs to come out again in order to get to the filters and sender unit. As they say, an ounce of prevention is worth a pound of cure.

there are two sets of 2 filters right? My upper filters (webers) were new, but the lower filters were very crusty and old. Did you replace both?

 

[DiabloClyde]

Yes, there are 2 upper filters as shown in my above posts and also the 2 pre-filters that come out of the tank before the fuel pumps. Given they are located next to a vented panel under the gas filler tube under the car, there is dirt and water access in this area and so at least the outward appearance you are experiencing is they are dirty. I'm actually replacing mine tonight or tomorrow because I have the fuel tank emptied and this would be an easier task now than in the future, though I expect residual fuel to spill from the hoses. I have pans with kitty litter on the ready! I am not touching the fuel pumps since both are just fine and I've had no issues.

 

[DiabloClyde]

I was going to replace the prefilters tonight but noticed those clamps are 20.7R Oetikers, a single ear clamp of 20.7mm. I bought clamps for the rest of the fuel line which at the primary larger filters are only 16.5R. Keep in mind none of the filters needed or at 18K miles were called for replacing but for already being in there to get to my sender gasket. But had I done this all over again, just go ahead and replace the fuel lines and clamps too!

So, on to other projects like an oil and filter change while the car is up on jack stands.

I think Santa Claus is bring me a real two post hydraulic lift this Christmas. Changing oil and getting into the fuel project has been a Bear on jackstands.

 

[DiabloClyde]

Speaking of other projects while I get the right fuel line clamps ordered: my gas filler cap screws are rusty. This is odd because aside from the usual rusty muffler and exhaust clamps, there is zero other rust on my car. I was already in past the removed rear passenger tire and removed fender so I noticed the nuts for the screws holding the filler assembly to the car panel are fixed in place. That is, if you remove the bolts from the gas cap area, you can simply screw in new ones without having to get your hand behind this assembly to hold the nuts in place. I found four new screws and fiber washers at the local hardware store! They were M5-0.8 by 16mm and they fit a size 4 metric Allen wrench. All 4 plus washers were less than $2 and took less than 2 minutes to replace. Simplest fix on the car so far!

A few tips just in case: replace one of them at a time rather than pull all four out first. This ensures the whole assembly does not come off. Another thing I do onnpretty much every new screw, washer and bolt threads is to rub anti corrosion paste on them all. I neither want hem rusting again nor seizing in contact with dissimilar metals. Finally, while you are in there, apply some grease to the plastic locking rod. Can’t hurt and will lengthen the life of this locking mechanism.

 

[DiabloClyde]

Success! Leak fixed. It was either the sender gasket or faulty o-ring at the one large fuel filter, but most probably the gasket. Filled it up all the way this afternoon, literally until it was overflowing at the nozzle, and it is now dry as a bone in the sender gasket indentation and at the the fuel filters. So, time to put everything back including properly attaching the vacuum tank and electro switch which were laying loose inside the car when I got into this project. Net-net this was a critical issue that could easily have resulted in a fire and at least the loss of the car if not life. If anyone smells gas, as I did, stop and find the solution. I hope my posts help people in the future. Thank you.

 

[Dereiter]

It is great to read it. Replace the gasket and drive safe.

 

[DiabloClyde]

Today I finally put the car back together and back down off the jackstands. The car finds its 1,100 rpm idle much quicker now (say 2 minutes from 4 or so), and the temperature hits 80 Celsius very rapidly and stays there. It seems to start up quicker as well, so I deduce that the radiator flush and the new fuel filters actually did make a meaningful, noticeable impact to the car’s performance. A silver lining to the failed fuel gasket cloud.

Recall I removed panel 14, the one that is riveted in place. I did this to seek the fuel leak and clean up and dry out the puddling of fuel. For anyone who ever needs to get in there, it is riveted with around 15 rivets and also caulked in place with some serious goo. I drilled out the rivets using 1/8” inch bit, then used aluminum rivets and watertight / gas resistant caulk found at hardware store. I slathered anti-corrosion coumpound on all rivets and holes before sealing it all back up because these aluminum rivet attach the aluminum pan to the steel frame members. This panel would not normally ever need to come off of your car unless there was damage to the underneath or unless you have leaking fuel like I did. And no, I am not sure why Lamborghini factory used thick sealant along with the rivets to seal this aluminum pan in place. It is not an airtight compartment as there are also weep holes in this panel underneath, but I want to duplicate everything they did in keeping the car original.

 

[AngelOfMurci]

@DiabloClyde
I filled my tank for the first time.
That night, my garage smelled of mild gas fumes.
The smell cleared up within a couple days.

I’ll be seeing if I can place a snake camera into the areas a leak could come from… sender gasket area and the fuel filters

thanks for the heads up!

 

[AngelOfMurci]

@DiabloClyde
I filled my tank for the first time.
That night, my garage smelled of mild gas fumes.
The smell cleared up within a couple days.

I’ll be seeing if I can place a snake camera into the areas a leak could come from… sender gasket area and the fuel filters

thanks for the heads up!

I’m guessing it’s related to something high at or above the gas tank, since it’s related to a full tank.

 

[DiabloClyde]

Like I said in my write up and the other thread, the sender gasket is attached to the gas tank in an indented area that is approximately 2 inches lower than the top of the gas tank meaning when full, the gas level is above the gasket level, which means your gasket is seeping gas Into the indented area on the top of your gas tank. This is a very dangerous condition. Best to snake your camera or Boroscope in underneath the coolant expansion tank on the right side of your engine to see.

if so, the “while you’re in there” fix it list is fuel filters, fuel lines, sender? Or at least gasket, new coolant lines at least in that area, check power steering fluid reservoir.