97 1.9 Z3 Overheating

[Cardriver333]

I think one of my coolant pipes broke so I replaced 99% of my cooling system (radiator, water pump, thermostat, thermostat housing, both coolant pipes, heater core, and all of the hoses) with new parts and am flushing the leftover coolant by filling the radiator, driving until the temp rises, draining the radiator, and putting new distilled water in and repeating these steps.

I was driving along and the temp was getting close to red so I drove home. The upper radiator hose was pretty warm and the lower hose was pretty cold. What's most likely the issue? I'm thinking air in the system, water doesn't cool it enough, or there is some blockage because the fluid that I first drained out looked pretty dirty

 

[Trevor /chedder]

I've seen people discuss putting the front of the car on ramps to clear air locks. Just a thought

 

[AntStark]

Yip might be an airlock..my garage had to lift the front of my car slightly to clear mine when replacing the coolant

 

[Andyboy]

I've never had to do any of that lifting palarva - just refill the system properly, i.e slowly. Air locks are caused by just tipping coolant in.

If the heater blows warm air, it's bled. If it doesn't, it isn't.

With it cold, disconnect the top hose from the radiator. Bleed screw out, rad cap off and pour coolant nice and slowly down the hose into the engine. You'll see the coolant level rise in the expansion tank as well. When the hose is full, refit it, wash all the excess coolant off, fire it up and run it at 2000 rpm with the heater on full heat and the bleed screw open slightly. It will take 2 or 3 minutes for the heater to start blowing arm air. As soon as you see coolant coming from the bleed screw, close it (a coin is ideal). When then heater is hot and the temp needle is about central, it's bled.

This is the quick way of doing not - the slow way is to just add a litre at a time with the bleed screw out, leaving 60 seconds before the next one so the air can escape and coolant can find its own way.

 

[Zephyr]

What @Andyboy says is the golden rule.
Further to that and for extra checking you can plug and odb scanner and monitor the circulation of the coolant.
there is a sensor showing the thermostat temperature and another showing the temperature at the circulation of the fluid.
both will be reading -40 degrees C (or whatever this is in Fahrenheit) and when temp of the thermostat (front sensor) reaches 108/110 the rear one will start to climb maybe up to 80 or ninety. Then the valve reading will turn to “on or circulating” and finally the fan will kick in.
in warm climates this procedure saved many engines as sometimes the rear sensor that reliefs the systems is sometimes faulty. (And the hose that circulates the fluids remains cold).
i hope what I said makes some sense.
if not I can post a video if needed.

 

[Cardriver333]

So my heater is working which makes me think the water I'm using to flush the system is getting hot enough for the guage to get close to the red instead of staying straight up and down and my hope is that when I'm done flushing and I fill it with coolant it won't get as hot.

Here's what the coolant pipe looked like and so does the inside of the block part of the cooling system. Is there a better way to clean it out, because right now I'm just filling the radiator with water, driving until it gets up to temp, let it cool, flush, and repeat

 

[Cardriver333]

I added some g48 and so far the needle stays vertical. I am still concerned about the crust in the block. Is there a good product to clean some of that out? Is the prestone radiator flush ok to use on this car? Thats what I've used on some of my other cars

 

[IainP]

If you want to flush it just remove the thermostat, connect a hose to the rear connector and run the tap for five mins.
The rust residue is caused by someone running the car with just water, or poor quality antifreeze. To get rid of that you need a cleaner/mild acid, then flush, then correct anti freeze mix.
Be aware that connector you show disintegrates with age. Also, turn the connector on the small hose, it’s stopping the larger rubber hose fitting fully onto the connector.
I’d just follow Andyboy’s info, it’s spot on.