I have took the plunge and changed the coolant on my FD today.

I purchased a lassie funnel to assist in the burping procedure. All went well and I warmed it up until the fans kicked in revving it to 3k occasionally.


I will admit I did this for quite some time, maybe 30-40min, but then out of the blue it started boiling out over the funnel. Up until then all was good not many bubbles.


Did I leave it to long with the funnel attached?? After it happened I left it for a bit and then started the car again and it did it again

Now at no point did I fill the funnel over 1/3 but it kept pushing fluid out until it spilt all over the engine. Also the temperature gauge never moved over half way which was odd.

Can anyone advise??

 

Im thinking it was just air pockets in the cooling system that was leaving.

 

The coolant was definitely boiling, like a pan on the stove!

 

How many miles on your car? That is quite strange.
I ask how many miles but really mean what's the condition of the engine? I'd guess coolant seals would let pressure into the radiator making a boiling and overflowing. But that's simply worse case scenario. Have you checked all your coolant lines for leaks?
Do you have a water temp gauge-I mean aftermarket-installed on your car?

 

Does it make a difference if the system is pressurized (radiator cap on) or not?

 

I'm pretty sure the pressure with the radiator cap on raises the boiling temp of the coolant .............

I could be wrong tho.

 

Yeah, having the cap on raises the boiling point of the coolant. It could be nothing to be honest. I can't remember if my car did that regularly without the cap on, but I think I might remember it being normal. I'd go check for you now except I'm in the middle of a vacuum job, D:

 

Thermostat, thermostat, thermostat. When there's an air bubble on the inside loop, it takes longer for your thermostat to open (there's a possibility you may have overheated the engine doing this.) When you turn off and restart the car (i.e., stop and start the waterpump) while hot, the thermostat almost automatically reopens. I've used that trick to verify burps on systems several times, including cracked heads introducing exhaust gas and trapping the t-stat. That DOESN'T sound like you, for the record.

Let it cool down, grab a rag or old t-shirt to throw over the worst of the boiling, and try again. Don't put coolant into the bucket unless it looks like the radiator's pushing dry. Things you should look for are:

1. vacuumed radiator hoses. If they flatten out with the cap on, you have pressure problems, proceed to step 3.
2. overheating. Try to keep an eye on the gauge as much as the coolant, or get someone else to watch it for you.
3. Pressure test the system.

If you emptied it enough to dry out the heater core, then yeah, this'll take a while. And be an epic pain.

 

I had the car checked over before purchase, and he said it was a strong engine. I have no details of rebuilds, the car has done 55k. However the compression results were mid to high 7's (bar, tested on mazda kit). His opionion was that it had had a rebuild 10000-12000 miles ago.

Ive only got the standard gauges. I haven't got that far yet!

Its really irritating as I had no issues before, the water quality just looked poor so I thought I would change it.

 

Soooo,

I spent the afternoon out in heavy rain following the burping procedure again.

This time I didn't give it to much beans, I just left it to idle. I took in quite a bit of fluid actually, which wasn't surprising as it chucked a load out yesterday!

I left it idling until the fans kicked in and then shut it off. I left it until quite cool with the funnel connected and 1/3 full of fluid.

It still continued to take in fluid. After a couple of hour I put the cap back on, and took it for a spin.

I will leave it until tomorrow and have a look at the fluid again. Hopefully we've cracked it!

Interestingly, before I took it for a spin I had to drain some fluid out of the expansion tank as it was way above the full mark on the dipstick.

 

I have limited knowledge, but in my cooling system research I've heard more experienced members on here say that if the overflow tank, well, overflows, (as in the fluid is not getting sucked back into the system as it cools), could mean either bad radiator cap(s) or something more serious like a coolant seal.

 

Bingo. If you're pouring more and more coolant in, but it's overflowing the expansion tank and NOT overheating, you have flow/pressure issues. Could be the cap, could be the thermostat, could be air in the system or a failed seal/hose. (And not just a leaking hose, but potentially kinked or clogged.)

Sounds like you're getting there. What'd the temp gauge look like while you drove it?