A2: how hot do they run?

First Things First!

Replace the sensor at the bottom of the rad for the cooling fan. My '90 Jetta turns on it's fan right as it hits the halfway mark. Your Jetta should do the same. One thing to remember is that water WILL BOIL. Not saying that G-11 won't, but if you have just water in the cooling system, expect a blown head gasket soon. Spend the $12 on a jug of G-11 coolant from your local VW dealer and get the water out. Secondly, if the temperature in your local drops below freezing, the water will crack your cylinder head and block if it freezes in the engine.

In short, I would worry about the car overheating until I had the proper coolant in the engine.

- Peter

It's an '89. This is a miracle :)

If the seal in the water pump is shot (you didn't mention where it was leaking), the system may not get to pressure; stop-leak stuff will not work here.

I'm against all stop-leak compounds in the cooling system. I clogged a rad once using the prestone stuff. YMMV but it's not worth the risk IMO.

Factory is 192 F isn't it? The hotter, the better. I wouldn't run striaght water...bad for hoses...surely someone will mention something about thermal capacities, transfer, etc.

A/C or defroGGer will turn on the rad fan. With pure water, the fan should come on quickly. Maybe the thermoswitch in the rad is shot (it's on the lower, driverside of the rad). Quick test: remove the switch (afterall, you're only running water), heat it with a torch and see if the fan comes on. Also, bridge the connector itself to check the circuit.

Not if you replace the water with a proper mix.

Allow me to disagree.

On my previous car (Fox'87) in addition to daily commute to work (48 mi. in LA) I was burning 2-3k every month on desert roads (paved+unpaved) mostly in Mojave. That car never saw a drop of coolant in 7 years, just tap water. The engine never overheated, never had any kind of problems related to cooling system, same water pump, same gaskets, same hoses. It's true that I rarely run the A/C. Only one time engine boiled over and threw all the water out is when I run over an underestimated thick bush which pull the wire from the radiator sensor (the one at the bottom) and the fan didn't run. I noticed that about 6 seconds before engine spit all the water out. But this was my fault. After the car was totaled in a crash I took all the good parts off the car before sending it to junk yard. That included engine head and radiator (which lived three more years in my second Fox). I looked inside the block, mineral deposits, what mineral deposits. I still have the water pump somewhere in a box. And the entire collection of hoses.

In LA there were occasional overnight drops to -4 -6, and the car was always parked in the street. The water does not have the time to freeze and crack the block when it's only that cold. Coolant is necessary only in areas where there is a real risk of freezing. And that means that it has to go way down below zero. The rest is a waste of money.

Peter Cressman wrote: but if you have just water in the cooling system, expect a blown

Jim B.

my 2 cents:

Water will provide better cooling but lacks corosion inhibitors and has the ability to freeze. Freezing in an engine is a bad thing because water expands when it freezes - fill a glass jar, cap it and freeze it to see what can happen.

Water, depending on the source can be high in minerals which is a bad thing according to some. There is a debate between people I know on what is best - destilled , r/o, or deionized. One line of thought is that water low in mineral content will dissolve more minerals from the engine. Personally I don't know what to believe.

As for corrosion inhibitors Redline (famous around here for their synth transmission oil) sells a product called WaterWetter which adds corrosion inhibitors and improves heat transfer to both plain water and antifreeze mixes. Check it out here

. Boiling, yes water will boil, so will antifreeze, but under pressure the boiling point of both is raised. With a 15psi cap the boiling point of water is about 250°F, 50/50 glycol is about 265°F.

To sum things up, IMHO the primary function of antifreeze is to keep the coolant from freezing. Given the choice I'd run water with an anti crossion agent added, but life in Southern Ontario doesn't allow that without a big risk, one I'm not willing to take.

Jeffo

It's totally true and I agree with you on all these, but I speak from my own experience, not from theory or what others said, unless I'll specify that. If you remember how the temp. gage is on Fox or Jetta/Golf, the needle never went past the warning light. Only when I was going uphill in Panamint range the indicator will go past the light. And that's a steep incline for that small engine. That means I was within safe limits all the time. Yes, water corrodes the block, but so insignificantly that probably you need to keep the car over 20 years to see any adverse effect. Yes, the antifreeze raises the boiling point, but the difference is relatively small, if you ignore the marketing hype, and I can live without it. In LA where I lived for long time, when temp. goes down overnight, below zero, it doesn't mean that between 8 PM and 6 AM was -6. The temp goes down gradually and will reach the lowest around 4AM. The car doesn't cool down as fast as the air around, unless there is a blizzard or such. So when the air outside is at -6 the engine is safe enough above the danger zone. And in few hours it's gonna start warming up anyway. Calcium deposits, of course there were calcium deposits, but again, insignificant. Remember that radiator lived 3 more years in the next Fox until I managed to impale it in a wheelbarrow handle. So actually I can't say how long would have lasted. All these are not to be taken as an advice for anybody, do what you want and what your heart and pocket let's you do. This is only my own experience and what I've been through. But the theory doesn't always match the real life needs.

snipped-for-privacy@doesthisblockporkmindspring.com wrote:

FWIW, my '91 GTI's needle goes to a little to the right of str8-up before the fan comes on by itself.

I recently had to replace the fan thermoswitch though because the fan quit working under normal "too hot" conditions and like yours only came on when the A/C was switched on. Put in a new switch and it now works.

There's also a relay at the top of the radiator as well. It also could be bad. It's cheap...under $5 at your local dealer.

Mine (86 GTI) was running just above the warning LED but still touching it. Seemed to me though that it was getting higher so I just recently bought a new 70 degree model Now it's below the first tick mark.

I already have a new waterpump and radiator (parts are extremely cheap comparied to my 944) and hoses.

By thanksgiving I'll have the new head on it...

I'll chime in again in the off chance that someone can help me. My temperature guage hasn't worked since VW working on an electrical problem about 2 years ago. Sensor is new and working but even if I bridge the connector, no rise on the dash. Do the wires go through the fuse box and then the cluster or directly to the cluster?

Darryl.