[Photoman]

1997 Landcruiser.
Here is a simple mod to monitor low coolant tank and low windshield washer tank contents. Yesterday I went to the farm supply and stopped at the U-Pull-It yard on the way back. I got the sender from something like a 97 Buick and one from a Cadillac. They were very very common. I got three at $3 US apiece. They mount by just pushing them into a hole grommet fashion. I drilled a 1 ½” hole in the coolant overflow tank on the radiator side. If you do this favor the front of the vehicle side very slightly as the tank is sloped this way a bit on the bottom. If you hit dead center as I did, not to worry as it will still work fine. What I would recommend is running the wiring through a delay timer set for maybe a minute. This way you have to be more truly low on fluid as opposed to sloshing. In other words the fluid must read low for a minute before the alarm light comes on. The timer I used is an ELK-960, although you can use what you want. The Elk-960 can be found at Hosfelt Electronics for $19.95. Search for ELK-960 and look at the bottom of the page. I wired the timer up so it worked but was concerned as the relay was staying on. I talked to ELK Electronics (great people) and they provided me with a better solution. See wiring pic.
The coolant tank holds 36 Oz. at the full line; 6 Oz. at the low line. The sender can be modded in a couple ways. As seen in the pic, heat the female part a little to make it easier to pull apart. One way to lengthen the sender is to just put in back together one click. This will lengthen it about 3/8” and the alarm should come on with about 2” on fluid left. Maybe use a little epoxy. If it is lengthened with the universal vacuum coupling it makes the alarm come on at about 1 ¾” from the bottom which is 12 Oz. left. I think either the little extra weight of the adapter or just the sender slide not working smoothly causes the discrepancy as the adapter legthens the sender about ¾” and is really about as low as it will go.
My washer bottle is really buried so it was hard to see and measure, but I think this mod should easily work with it. From the measurements I could get, the length might have to be changed a little.
One caution is I don’t know how the sender will handle hot rad water as opposed to washer water.

Bill

[Photoman]

Wiring

[Cruiserhead05]

Your ridiculous photoman....hurry up and get on the list for ROTW

[Heffenoche]

Nice write up, thanks for the idea.

[gbell210]

FYI - if you aren't sure about the sender with hot coolant, check some mkiii (86.5-93) supras. These have an overflow container float sensor that illuminates the "bird cage" or radiator light on the dash when the bottle is low. The sensor on these are located at the bottom of the bottle though, not the top like that GM one.

[IdahoDoug]

Bill,

This is something I've been wanting for quite a while - a low coolant indicator essentially. And one that will react quickly. Well done - I'll be doing mine this summer.

DougM

[concretejungle]

Photoman, you never stop amazing me with your enginuity (sp?), but i wish you would knock the dust off of her and take her out for a spin!

[Beowulf]

Resurrecting Photoman's thread.

I did part of this mod this weekend.






As Bill suggested, I drilled the 1-1/2" hole toward the front of the tank.

I have not hooked up the electrical. Planning to use a small 12v LED in the pod with my Greddy gauge. I did a little testing with the meter and I am not planning to do the timer delay circuit. The coolant can slosh around in there a lot and I don't think it will be a problem... live testing to follow.

Wiring to the gauge pod should be relatively easy. Ignition switched +12v to one leg of the LED and run the -12v lead to the NO sensor wire, then to body ground next to the aux battery.

The sensor that I picked up came from a 1996 Cadillac. They have a huge washer fluid resevoir under the left side front fender. You will notice this sensor is different from the one Bill showed; it has a much smaller bulb at the end so I had to rig up a longer extension to put it in the bottom of the stock 80 overflow tank.

-B-

[lt403]

great idea

[Boston Mangler]

very good idea!

[Rich]

If one wants to cover all the bases one could set up another sensor to monitor over full. Often the first sign of a leaking headgasket will be the resevoir overflowing while underway.

[MoJ]

I've never looked at how the window washer fluid level sensor works but any reason that couldn't be used? Mount a 2nd sensor on the overflow tank, wired in series with the window washer sensor so that the already present instrument light would signal a low level of either fluid?

[Beowulf]

MoJ,

My '97 does not have a window washer fluid level sensor. I also don't think it has a dash light for it.

BTW, the blue line on the white bulb is the fluid level when the bouyancy of the bulb will close the switch in the cap.

-B-

[semlin]

Originally Posted by Rich

If one wants to cover all the bases one could set up another sensor to monitor over full. Often the first sign of a leaking headgasket will be the resevoir overflowing while underway.

To throw further "cold water" on this mod, I hate to say it but the overflow tank coolant level was completely normal on my truck both right before and right after the truck boiled dry from a tiny leak. The before part unfortunately fooled me into thinking I still had lots of coolant. It is a very ingenious mod and may work in some situations but it would have done me no good at all.

[Beowulf]

Simon,

Are you saying your coolant level in the overflow tank was normal and your radiator was empty? Was the coolant pickup tube in the overflow tank blocked?

-B-

[Rookie2]

Originally Posted by Beowulf

Simon,

Are you saying your coolant level in the overflow tank was normal and your radiator was empty? Was the coolant pickup tube in the overflow tank blocked?

-B-

Is it a coolant reservoir or a coolant overflow tank? I thought that it functioned as a reservoir in that if coolant was lost from the system, fluid is pulled from the coolant reservoir tank until it's empty, making this a logical mod.

[semlin]

yes I am and no it was not blocked. i pulled into a parking lot and felt a slightly rough idle so i popped the hood. i noticed a slight drip leak on a heater hose so i checked the overflow. it was at a normal level and passed a bubble test. i stupidly figured the leak was recent because there was only a tiny amount of coolant underneath it on the exhaust shield, and since temp was normal I figured the rough idle might be plugs or something and decided to check when i got home. 1/3 mile from parking lot is a bridge on ramp. By the time I was on the bridge my temp started moving. I stupidly tried to baby it at 5 mph over the crown because it one of the busiest bridges in vancouver and a dangerous place to break down. by the time i got to the crown of the bridge the temp gauge was spiked and I coasted down to the other side and pulled over. once it cooled down i could see my rad was dry. no blockage in the outflow and it was still half full of coolant. later after changing the hose and refilling the rad the overflow blew bubbles like crazy.

[Beowulf]

Originally Posted by Rookie2

Is it a coolant reservoir or a coolant overflow tank? I thought that it functioned as a reservoir in that if coolant was lost from the system, fluid is pulled from the coolant reservoir tank until it's empty, making this a logical mod.

My understanding is that it's both a reservoir and an overflow tank. And I believe your assumption is correct.

As the coolant expands, it is forced into the overflow tank. As it cools (after the engine is shut off) it is sucked back into the radiator. I would have to go back and read but I am pretty sure on both of Doug's trucks (97=cracked head & 93=HG failed) he initially noticed the coolant resevoir was low.

Simon,
Maybe I can talk Photoman into doing a mod to make the sensor into a bubble detector?

-B-

[Photoman]

As my first sentence says, this is just something to let you know if the fluid level is low in the coolant or washer tank, not a head gasket failure detector. Sometimes a cigar is just a cigar.
When my block cracked, I did not realize the coolant level had dropped. The next day the temps started to go up and I saw coolant tank was empty. This mod would have warned me there was a problem, but would not have prevented it from happening. It looks like Semlin made it about a mile with a catastrophic failure so whether a warning light comes on or not, you’re still done for the day. So, it may help as an indicator of problems; or, that the fluid level has not been checked in five years and a little juice needs to be added.
An idea for Rich’s suggestion for an overflowing coolant tank indicator would be to just tee a low temperature value temperature switch into the overflow hose and use a relay for the warning light or buzzer. Not much sense closing the door at that point though; the cow’s already out of the barn.

Nice job B. Let us know how the testing goes.

Bubble detector? When I used to dive, if your eardrums burst and you got vertigo you were supposed to feel for your bubbles. This would tell you which way was up. I tried it once but went down instead of up. Guess I was grabbing the wrong bubbles.

Bill

[semlin]

Bill, i'd like to hear more about the block cracking. one detail omitted from the story above is the nasty clattering i heard when i first turned it over after putting more fluid in. I believe it was a blown and broken h/g ring protruding into the cylinder impacting on the cylinder as I have nice little gouge in the cylinder when i opened it up but I am not sure. did you crack your block from loss of coolant??

[Scamper]

Originally Posted by Beowulf

My understanding is that it's both a reservoir and an overflow tank. And I believe your assumption is correct.

As the coolant expands, it is forced into the overflow tank. As it cools (after the engine is shut off) it is sucked back into the radiator. I would have to go back and read but I am pretty sure on both of Doug's trucks (97=cracked head & 93=HG failed) he initially noticed the coolant resevoir was low.

Simon,
Maybe I can talk Photoman into doing a mod to make the sensor into a bubble detector?

-B-

I think the issue may be that it's an expansion tank. The radiator cap allows the system to be pressurized, and as the coolant expands, any excess will be driven into the tank. However, since the presence of any coolant in the system will allow it to maintain pressure while hot, there may well be no "retrieval" from the expansion tank, and so the level in the tank would not drop until the system cools down, at which point there is contraction and a vaccum is created. Under these conditions, I can understand why Simon would not have detected the low coolant situation.

That said, if your truck were loosing coolant slowly, then the sensor would indicate at startup if you were low so long as sufficient time had passed to allow adequate cooling. That would be the time to catch it.

[Photoman]

Quote from Semlin:

Bill, i'd like to hear more about the block cracking. one detail omitted from the story above is the nasty clattering i heard when i first turned it over after putting more fluid in. I believe it was a blown and broken h/g ring protruding into the cylinder impacting on the cylinder as I have nice little gouge in the cylinder when i opened it up but I am not sure. did you crack your block from loss of coolant??

There were no symptoms on mine other than the loss of coolant. I left for a trip and made it to Washington from the East coast. Each morning I was adding a quart or more of anti-freeze and noticed it weeping at an expansion plug on the DS. The cruiser only had 29k miles on it, so I took it to a dealer north of Seattle. First they replaced the expansion plug and the leak did not stop. So I had to cool my heels for a week while they replaced the block. I looked at the old block and could see a small crack in the casting at the bottom of the expansion plug hole. I attribute the crack to me having to run the cruiser at high RPM’s for sustained periods. The thing was so heavy, I was in second gear some times floored for tens minutes to get up some of the hills on the interstates. The engine would rhythmically shutter. When I got back I talked to TRD and the superchargers were about to come out so I got one and installed it. The dealer did not know the cause of the crack and what I said is just a guess.

Bill

[alaskacruiser]

Cool mod.Speaking of a low coolant reservoir, this recently happened to me as some of my lower heater hoses started slowly leaking. I noticed my digital temp guage readings started climbing from the normal 190 to around 214 and immediately popped the hood to find an empty coolant reservoir and my rad approx. 2 gallons low. Considering my temp guage is about 8-10F > OBD, I was pretty safe.

[boydmick]

Another thing to consider:

If you have a leak in your cooling system, as the system cools it may not draw coolant back into the system from the overflow bottle.

Air can enter the system through the leak, leaving your overflow level unchanged.

Still a cool mod!

Boyd

[alia176]

You know, we *could* use the dirty air filter indicator in the dash for the "coolant low level" indicator! It's the one to the right of the front and rear diff locked indicators. I did put a bulb in that spot when I added the diff locked bulbs. All you gotta do is switch GND and you're all set!

Just a thought!

Ali

[NLXTACY]

Resurrecting this thread. Just received the ELF960 in the mail today. So now looking back, anything that you guys would have done differently now that you have been running it for a couple of years? Also, where did you mount the ELK and did you enclose it in a kit box or something? I have to remove the instrument cluster anyway so I was going to wire up a red LED "inside" the instrument cluster just under the temp gauge.

Joey

[Beowulf]

Other than the Mr Wizard factor, the ELK timer circuit is not needed. I have been running "un-timed" for about 2 years. No flickering light. No intermittent light. I would not do anything differently and I would do the mod again.

I test it about every 6 months (due for another soon) and the low coolant level detector still works fine.

-B-

[beno]

Please tell me that you guys are not actually putting coolant overflow and washer bottle height sensors?

Sorry. Nothing against Bill or anyone that might have already done these "modifications" but seriously, can't ya just get out of your air conditioned rig, pop the hood and look at both containers?



Just sayin'.

[NLXTACY]

Beno...in a word...TOTALLY!!!

I'mm looking to automate everything so that I don't have to open the hood again. Hmm, I COULD also strap a jug of antifreeze to the overflow tank with a pump so that when the light goes on, so does the pump. Light goes off, so does pump. Viola! Always have enough coolant :P

Ok I'm not going to do that...but thought about it.

[Cruiserhead05]

I can see it beneficial is traveling down the highway for a long period of time. You spring a "slow" leak and eventually lose fluid. Perhaps this would notify you of the problem before the truck loses all fluid and potentially overheats?