TheSamba.com :: View topic

Sun Jul 18, 2010 1:29 pm

My temp gauge works fine(Except for blinky :evil: ) I'm looking to add an aftermarket gauge to get a better reading in my 1984 1.9, would it make sense to tie it in where the bleed screw is on top of the radiator? Instead for running all the way to the back. Will that be an accurate reading? Thoughts, concerns, opinions?

Sun Jul 18, 2010 3:55 pm

You're really concerned with the temperature of the water as it leaves the engine, not as it flows through the radiator (I assume). If that's true, you really need to find a place on the engine to read the temperature.

pd

Sun Jul 18, 2010 4:44 pm

With my limited knowledge but recent experience yes I'd vote for in the back. I suggest a metal T close to the engine.

I'd like to ask a question: What is most important, temp going into engine or temp coming out of engine?

Sun Jul 18, 2010 4:56 pm

Volksaholic wrote: You're really concerned with the temperature of the water as it leaves the engine,

What he said.

Sun Jul 18, 2010 5:05 pm

Yeh :oops: me missed that. Bad me. Sorry I didn't ask that correctly. IF there were a temp gauge on the fluid going into the engine and one coming out of the engine, how big a difference would there be in the temps? I am assuming that the in temp should be lower and that is what coolant is for. Any value in measuring this difference? I suppose climate and air temp could affect this input temp? Is this even feasible? Which one affects the oil temp.?

I'm specifically wondering re my TD with extra oil coolant and recent negative experience.

Sun Jul 18, 2010 6:24 pm

You're basically correct that "that's what coolant is for," but actually that's what the radiator is for. The coolant picks up and transports the heat from the engine to the radiator which dumps it to the atmosphere, the sends the coolant back for recycling. You care about the coolant temperatures in the engine or just as they leave, because that's where the damage is going to occur if you loose or overheat your coolant.

I don't believe there's a direct correlation between oil temperature and coolant temp, although there's and indirect relationship (if the engine's working hard, they both heat up, when the engine's off, they both cool down). I just installed oil pressure and temperature gauges on my Subie conversion... maybe I can give you some better real world experience in a few weeks).

Oil temperature matters because it needs to be at "operating temperature" to provide the proper viscosity for lubrication, but petroleum based oil will break down if it overheats. One of the things I like about the 2.1 Wasserboxer and Subie turbo and 3.0 engines is they have an oil/coolant heat exchanger. That should bring the oil up to operating temperature faster on cold January mornings but help keep it within operating temperature doing 80mph across the Mojave Desert in July. My engine doesn't have that, so there should be less correlation between the two temps on my gauges.

You can sort of monitor the temperature at the radiator already: listen for the fan. If the A/C is off and everything is working properly, the fan will kick in at about 203º F. It will kick up to second stage at around 216º F.

Paul

Sun Jul 18, 2010 8:18 pm

That helps me. I will now try to corelate my temp gauge with the rad fans 2 settings. I'll try, don't know if I'll hear it. Well that is when I get my transplant which is now rescheduled to Thurs.

So is it feasible to have a temp gauge connected into the system aft of the rad flow. Would this not demonstrate how well cooling is happening AND wouldn't it let you know if the temp coming out of the rad was still high therefore higher than normal going into engine in certain climatic/geographical conditions? And if that was happening would just a slow down in speed help?

I know it may sound like I am belabouring this issue but I want a clear understanding of the route of the coolant and its various temps OR should I just rely on reading the after market temp gauges for water and oil temps and oil pressure. Alas this did not help me a few weeks ago. I guess I'm saying is that I'd like to know before something bad is going to happen and be able to shut her down. Now remember guys I don't have your technical experience and knowledge.

Sun Jul 18, 2010 10:09 pm

I am thinking that there is correlation between water and oil temp. My water temp for long highway trips is way lower after adding an oil cooler. I'm pretty much sitting fully below ole blinky now where before I was at about half way up the gauge.

Mon Jul 19, 2010 8:22 am

I would expect there to be a closer correlation with the WBX oil/coolant heat exchanger. In fact, I noticed that my Subie water temperatures run at about the blinky light on the gauge (around 190º to 200º) whereas the 2.1 WBX ran in the upper half. I wonder if this is due to the heat exchanger, or if the WBX just generates more heat. My '85 1.9L didn't run as hot as the 2.1L... or at least didn't run as high on the gauge, but maybe the temp sender reads differently. Now that I think about it, I don't know if I'm driving the gauge with a 1.9L or 2.1L sender... that may skew my comparison.

As I've said before, I think the heat exchanger is a good thing... I'd rather the coolant took the bulk of the heat out of the oil and let the oil do what's it's there for... lubrication*. I may add a heat exchanger to my Subie engine at some point because that's the one step backward that I think I've taken with my conversion. I also think for the mixed climates I drive in a heat exchanger is much more sensible than an oil cooler if I were choosing one or the other.

FWIW: driving last night in mid to high 90ºs my water temps were running between about 190º and 200º and oil temps ran a pretty steady 210º to 220º. That's not really pushing it hard, it's only one sample, and it's not the same as what I'd expect from a WBXer, but I thought I'd put it out there for reference.

Paul

*That's a generalization... the oil is actually there to transport heat from the pistons and bearings as well as lubricate, but the coolant's only purpose is to moderate temperatures.

Mon Jul 19, 2010 8:28 am

DAIZEE wrote: I know it may sound like I am belabouring this issue but I want a clear understanding of the route of the coolant and its various temps OR should I just rely on reading the after market temp gauges for water and oil temps and oil pressure.
I wish I could rattle off how the coolant flows in the WBX engine, but it's the most convoluted configuration of hoses & pipes I've ever seen on an engine and I think I've already blocked it from my long-term memory. For those Steam Punkers amongst us, it's probably a thing of beauty. That's one place I think I've moved way ahead with the conversion: the Subaru coolant flow is logical, refined, and somewhat minimalistic.

pd

Mon Jul 19, 2010 8:40 am

Now I'll ask a real simple question which will really be about opinions.

Why not an extra water temp gauge exiting the radiator as well as a water temp gauge exiting the motor? Does it do any harm? If it makes someone less paranoid but also give multiple readings which could indicate problems more accurately before any episode. Is it stupid to install a water temp gauge aft of the radiator?

Mon Jul 19, 2010 10:00 am

DAIZEE wrote: Why not an extra water temp gauge exiting the radiator as well as a water temp gauge exiting the motor? Does it do any harm?
I guess you've asked this question a couple times. In my opinion... no, it doesn't really hurt anything. It's an additional expense, but if it's useful information to you it could be worthwhile. Some folks don't want any more than what the van shipped with, some folks don't even look at that, and some folks (like me) like to have more info. You could even use one gauge and switch the input between the two senders to keep the cost down. Just don't get so enthralled with your array of gauges that you drive off the road! :)

Paul

Mon Jul 19, 2010 10:05 am

I hear you but it is a gauge that wouldn't have to be in your face. I have four on the dash now. But if one noticed the rear water temp gauge rising one could then monitor the forward one. It's just that I'm paranoid after what happened AND I don't have a sense of smell so I don't know what's always going on until it is REAL obvious.

Thanks for all your inputs and knowledge!

Mon Jul 19, 2010 10:30 am

DAIZEE wrote: I hear you but it is a gauge that wouldn't have to be in your face. I have four on the dash now.
I know... I'm not dissing gauges. Ideally they should all be where you can see them in your peripheral vision while you drive, or have the road in your peripheral vision while you glance at the gauge. I didn't want to add mine to the top of the instrument cluster or dash so I stuck them in the "TenCentLife" location from a thread long ago (heater cover below the dash). I angled them toward the driver's seat (I'm going to post pics when I have time), but that's still a dangerous location if it's something you wanted to constantly monitor. For just glancing down when I'm really working the engine, though, I figure it will be okay.

pd

Mon Jul 19, 2010 11:03 am

My thoughts were having something with actual numbers is nice, even if it not ideal tied in to rad. i'll call it a backup. Considering how temperamental the stock gauge can be if i look down and its reading way hot i can then look at the secondary and not just go with the (maybe) the stock one is just having a bad day, AGAIN. But maybe i'll just find a gauge with a long enough probe. Can they be modified/ lengthened?

Mon Jul 19, 2010 11:17 am

TIMMAGON wrote: maybe i'll just find a gauge with a long enough probe. Can they be modified/ lengthened?
For any of these rear-engined beasts you want and electric (electronic?) gauge rather than mechanical, the difference being that you run electric wires between the sender and gauge. I don't know if temperature gauges are mechanical... seems kind of silly that they would be... but oil pressure gauges often times are. With an electric gauge you can run any length of wire you need to whatever location and back to the gauge. As I mentioned before... you could conceivably set one temperature gauge up with a switch to monitor oil, engine coolant, radiator coolant, and maybe even oil temp at another location. In general, though, you want to be able to glance at them without taking your eyes off the road, so switching may not be practical.

pd

BTW: I don't find that my Vanagon dash gauge is really finicky, but it can be tricky to understand what it's telling you. Since my Subaru engine has on board diagnostics, the ECU monitors the temperature separately from the dash sender. I can read the ECU temperature reading, which is coming from a sender a couple inches from the Vanagon sender and correlate the two. Now I know that the top of the light on my van is about 200º and that's been pretty consistent. If you got an IR point-and-read thermometer and took some readings from the hoses around the temperature sender you could probably calibrate how you read the stock gauge and I think you'd be pretty close.

Mon Jul 19, 2010 11:30 am

I like the added gauges which give you actual numbers and readings. Mine are not digital but numbers on a scale. I'm not sure I could go back to a reg temp gauge in the dash again (well I do in my Tercel) in a Vanagon. All my gauges are wired.