Dennis, thanks for pointing out the rtucker post - I've moved it to a new thread.
When we know if a life belt or DIY float works I'll précis this and make it a HOW-TO

 

Great work. Kudos to all!

 

While driving around today, I was waiting for a low coolant warning to appear, since my car has always had a great sense of irony. But it did not.

Life preserver idea: how about just a nylon washer or two under the current float. That might be all we need.

 

I thought about a supplemental float booster but decided it was just too wonky to pursue. Since others are intersted, however, here's what I came up with...

1. I could "glue" something to the top of the float easiest, but it would interfere with the top stop and put the magnet in a lower position relative to the switch. Recalling that the switch only opens/closes in a somewhat narrow band along it's total length, a life preserver that is too think could create a problem...

2. Dennis07 gave us a great idea! Putting something under the magnet is harder to do physically but has the advantage that it dosen't need to be affixed to the float - only push up against it. I presume the float always floats to it's top stop, and thus the magnet stays in the same relative spot regardless of what is below the magnet.

3. The tank itself is 12 years old, maybe I should just get a new one. Still, it is a $200 fix and the tank and the sensor aren't broken.

Here's where it gets dangerous...

4. I just went to the garage and checked Dennis07's idea: Nylon Anchor Washers float in water and in a 50/50 antifreeze mix. They coat $0.01 each... Similar, but thicker nylon spacing washers are also easy to get and cheap. (Zip ties and garden hose washers don't float. My girlfriend thinks I've lost my mind but is searching for "floaty things" around the house right now)

So...the post is maybe 3/8" in diameter. There seems to be some clearance to the tank wall around it's perimiter (Who has taken their tank apart - can they check this stuff?) So maybe the fit doesn't need to be very precise. The washers come in many sizes and perhaps can be made to "snap fit" around the post under the magnet.

For $199.99 in savings I'll try it. What else floats and would be easy to manipulate around the post? And not hang up - I want the system to still work properly if the coolant gets low...

I'll head to the hardware store tomorrow. If anyone has their tank apart and can take some measurements or post a picture it would surely be appreciated!

 

Try JagRepair.com In the XK8/R section is an article on the coolant tank with pictures. Might help see what you need to try this.

 

I have my entire tank and float in hand, what do you need?

 

The shaft that the float rides on is tapered and is hard to get an accurate reading but the inside measurement of the float opening is a little shy of 1/2in at 0.468 the OD is 0.899. The shaft that it rides on is 1.554in long but has a guard limits the floats movement to 0.454in this measurement is from the top of the float to the float stop. I hope this helps if not check your PM.

 

Maybe cork? I found a piece of old cork gasket material around the house., about 1/8 " thick. It would be easy to cut and manipulate in the tank. I am not certain about how long it would last though since it would become saturated after awhile.

 

Stick to something like expanded polystyrene.
It is 'closed cell' - unlike a sponge the air bubbles don't connect.
It is also pretty flexible. I'd guess a horseshoe superglued to the underside of the float would work or just a rectangle zip tied to the side of the float.
Nylon doesn't float - SG is 1.13

 

D'oh! Nice catch there.

Confusion here. I've got an assortment of these whitish washers that I always thought were nylon and they do float, but now I don't know what they're made of.

 

Petrified slices of a unicorn horn....

 

Thanks, Gus for the measurements - that's a help.

I went around the big Ace hardware in town - it has a very large selection of fittings, washers, grommets, spacers, etc. in a thousand little boxes along the wall. I had a cup of water and plunked everything that looked reasonable into it. Know what? Nothing they had floats - nothing. Not nylon spacers, rubber fender washers, faucet washers, fiber type washers - nothing!

Last night I found a 2 piece plastic grommet thing that you use to make attachment points in those cheap tarps. It floats (sort of...), is about the right size and after I snipped out a piece it will "snap" around the post under the magnet. It just dosen't float with authority - I believe it has virtually no lifting power.

I'm going to look around for a couple of more days. More to follow...

 

I like what you guys are doing. But one thing to keep in mind is that there is another problem with the float. We are looking at more floating power. Good. But there are cases and a lot of them where the magnet has come out of the float. One of our members from down under was able to put it back in only to have it fall out 24 hours later. Mine has also fallen out. All this tells me is that the float is actually deteriorateing. It is getting water logged and loses its grip on the magnet. If the approach is to cut the tank open and fix the problem I think it would be best to replace the float instead with something that will float and hold the magnet.

I wonder what the float was made out of in the Jag XJ6 95-97. Mine still works fine and I have not heard of this problem with those cars and the design appears the same. Same sensor. And mine is five years older than my XK8.

 

My magnet is still in place. I never considered cutting the tank open. I think trying to reseal it would lead to leaks. I don't think you can get only the float.
Perhaps removing some of the float material would give it more buoyancy? I don't know.

 

In the event that it's not possible to keep the current float afloat, maybe something here as a replacement ...
Floating Magnets, Float Switch Magnets - MEDER electronic

Haven't thought about this in detail; just poking around.

 

The only way to replace the float is to remove the top of the tank or cut the old float I would consider sealing the existing float. If the magnet is in question I am sure you could reinstall the old one if it fell out or replace it if necessary. If neither one is an option bite the bullet and get a new tank it is a lot less aggravation.

 

Well, the booster float ring snapped on the post, under the magnet on the first try. I left the tank in place and just siphoned off some antifreeze and had the thing working in less than 15 minutes. The float rises right to the top and stays there.

However, the Low Coolant message continues to appear 3 or 4 minutes after the first cold start of the day and extinguishes itself 5 minutes later, never to appear again until the next cold start. I have two things in my mind right now:

1) Could it be that nothing is wrong and the expansion tank really does drain itself low and then refill? If so, why would it start doing this? Others with this problem have watched their tank and not seen this. Does having the cap off to see make a difference in the dynamics of the fluid?

2) Or, is there come charactersitic of cool antifreeze that is different than warm antifeeze? Could warm antifreeze come into the cool tank and momentarily cause the float/magnet to drop? Again, why does it start now, after 13 years?

Somehow I think the magnet/float is behind all this but don't know exactly how yet. It may be a combination of things working together.

 

Well done, Scott!

What material did you use? ... Maybe I missed it.

On the cold start thing, I contunue to harbor suspicions about thermostat opening being somehow involved.

Suggestion for a simple test: cold engine, cap off. Watch the fluid level as the engine comes up to temp. There may be a level drop when the thermostat opens, or maybe not. But either way, we put the idea to bed. There should not be a coolant overflow if you replace the cap as we reach 180 degrees.

 

Well, I don't know what I used exactly, it was a plastic ring from a tarp I bought. Gus gave me the post diameter (0.488) and I clipped the ring into a "C" shape just a shade under that. It snapped on and floats great.

I will try your test. It makes sense in that the thermostat would likely only open once a day in this warm weather which parallels the problem. I'm thinking I will use a piece of clear plexiglass and some dialecetric grease to seal the opening while I watch in case that makes a difference.

Thanks!

 

And you were able to do this without opening (cutting) the tank. Everything done thru the existing fill hole? What did you use to get the ring into position and snapped on?

Any chance you took pictures?