Technical Engine overheat - airlock?

[chesh]

Hi all
1.6 engine.

Head was rebuilt 1 year ago, thermostat changed.
Today it overheat on idle to the max. some coolant came out the lower hose because of the pressure.
Both of the cooling hoses were hot, and fan was working (only 1 fan speed).

I let it cool down, opened the bleed valves and then filled coolant.
Almost 2 ltr was missing! ALTHOUGH coolant level was on MAX in the radiator!

I then started the engine with the radiator cap off
BUT, when I did that, coolant runs freely when the rad cap is open, and then I loss much coolant.

I closed the cap when I saw that, and then fan kicked in normally at half temp.

My question is why if I start the engine with rad cap off, the coolant doesn't stay at it's height, and wants to get out?
On all of my puntos when I did that, coolant didn't want to get out so quick and I waited until fan kicks in with the cap open.

Compression test is fine, about 170-180 on all cylinders.

 

[Chris parry]

Its still possible to be head gasket failure and have good compression.
Try a leakdown test (compression test in reverse). Because it sounds like you are pumping air/exhaust into the radiator!
See how that goes

 

[chesh]

I've done leakdown test on cold running engine,
result were fine, and blue chemical color didn't change.

Then connected pressure tester and let the car idle for 30 min with reving,
Pressure built up, fan kicked in normally and flew hot air into the engine.
but then pressure was high, and fan always worked.

Mechanical said it's the head or the whole engine.

 

[Mike1alike]

I don't think is the engine, nor the head.
I would recomand you to proper clean the cooling system first, a clogged radiator would make the coolant to want to get out.
This is the method I cleaned mine, with water and lemon salt, it beats any dedicated cleaning product that is in the market (most of them do very little cleaning).
Here it is:
https://www.fiatforum.com/punto-ii/484403-i-fixed-car-heater-little-radiator-inside-car.html

 

[FiorinoDan]

Also worth checking the thermostat again, then backflush the system to make sure there are no airlocks. An airlock in the system could well cause the water pump to pressurise the radiator.

 

[chesh]

I have tried new thermostat and the same
Fan starts OK on little below half temp.
Then coolant starts to go up the tank and at the cap when closed.
Then temp rise up to 3/4 and can go up if I don't turn it off.

All this time, the fan works, hot air comes to the engine, but it won't cool down.

I have removed the radiator but it looks almost NEW

Compression test shows:

CY 1: 175
CY 2: 165
CY 3: 150
CY 4: 165

is that ok?
CO in the water test shows nothing.

 

[FiorinoDan]

Airlocks ???????

 

[Mike1alike]

What about the water pump? How old is it? Maybe it is due for a replacement. If everything else is ok, no airlocks, the whater pump is the one you should take a look at.
Although you do have pressure in the system, not just overheat engine. Check the engine all around, you do loose coolant, that is the problem. Check the freezing caps, the metal pipe from the cooling system that feeds the water pump and all the hoses. You have to find where are you loosing coolant. How about the radiator's cap? It can be broke and that can be the problematic place where coolant gets lost.

 

[chesh]

Symptom is when the car is at half temp, coolant begins to rise up the tank and get pressurized like this:

I already changed the metal pipe from the water pump to the radiator
the old one didn't leak but still overheating.

Car is not losing coolant, well the coolant was always near MAX.
I have tried new radiator cap and the same.

I have removed the water pump today.
it is 7 years old BUT, it look fairly new. and it has iron blades and not plastic.
I will put a new pump but I think it can last many years.

Next thing is to remove the head and renew everything.
Should I just install all before removing the head and give it a third try?
I have tried to bleed it twice, with no luck.
I have filled coolant with the 2 valve caps off, when engine is cold. until coolant came with no bubbles.

*Heater matrix is disconnected*

I have heard I should lift the car a little so the tank will be higher than the heater valve, that might help?
when car is overheating, I open the heater valve a little and I get steam with no water.

 

[Mike1alike]

Yes, the water pump do last years and yours looks in good gondition and considering you do have pressure in the system, I'd say it works just fine, does not need a replacement.

I have heard I should lift the car a little so the tank will be higher than the heater valve, that might help?
when car is overheating, I open the heater valve a little and I get steam with no water.

Yes, that is true about lifting the front end of the car. And after topping the system while cold, you should start the engine (front end higher) keep the radiator cap open and let it run about 5 mins. Then stop the engine and open again the valves for bleeding (or the one valve in your case, if you say the heater matrix is disconnected), carefully because is hot. That steam you get is the air in the system, open the valve and wait until water comes out, then close the valve. If no water comes out, top it up, it will come, and after that, if the level is above max, take out what is above max.
Also, one other thing: make sure that the valve on the radiator's cap is functional and can open up, even if the cap is new (it can be stuck). It should open on pressure higher than 1 bar (it is clearly written on it so). So if you blow on the valve, you should feel the air coming through the gaps between thread.
And a question about the radiator's fan: is it really 1 speed fan, or is it's thermic fuse (on nr 1 sped) blown and the fan only works on the 2nd speed therefore the pressure is higher than normal? Check under the fans's connectors if there are 2 lines and that thermic fuse.

 

[chesh]

Yes it's 1 speed only fan.

I assume you mean this:

Mine doesn't have this piece.

 

[Mike1alike]

Yes, that one I ment.
Then, you should do the proper bleeding.
In regard of removing the head, I don't see anything pointing to that being needed. Your compression test looks good and no CO in the water also good. You can remove the head and renew everything there, but it does not look like the problem is coming from there.

 

[Mike1alike]

One more question about the radiator cap: does it have the gasket inside, the one ment to stop the coolant getting out, like in your first picture above? And also, is it properly tide?

 

[chesh]

yes it is.
I have tried with 2 new caps and the same.
Also removed the water pump base to the block today.
It is a bit rusty, probably never changed. I don't think it's the reason.
Will replace that as well.

 

[Mike1alike]

Was the thermostat last changed 1 year ago? If so, you should test if it is still working or just replace it with a new one.
And the radiator, it does look good in the picture you've posted, but are the pipes inside clean, not clogged? Have you test them, putting water through?
Before you get the head down, I'd recommend you make sure the radiator is not clogged. Either do a cleaning, either try one that you're sure it works fine.

 

[chesh]

I removed the head today
I will get it to the workshop to skim it.

How does the block look?
What should I clean it with?
Sand paper? Scotch brite?

 

[Mike1alike]

Search the forum, here or in the Mk2 area, people have done that and posted about it. If you use sand paper, it must be very very fine granulated. And it looks like you' put silicone before, to the gasket (or your mechanic did), usually to th HG you don't put silicone. As I've mentioned, check some other topics, you must find it nicely described, on this forum, with every step, what to pay attention to and all.