I need some mechanical help please

[terravista]

Hi learned people
My daughter has a Mazda 2 manufactured in 2005 auto 1.5 litre and has 120 000km on it. The car is going through radiator coolant at the rate of half a liter every three days while averaging 60km per day.
The mechanic checked it over and said it was the radiator. The radiator company checked it over and said it was either a cracked head or bad gasket after supposedly finding exhaust fumes in the coolant.
There is no change to smooth engine running as often happens with a cracked head. There is no evidence of leaking hoses or radiator while running, and no steam or moisture from the exhaust. The radiator cap seems to be OK and watching for coolant movement after cold starting it seems like the theromostat is working.
There is no oil in the water or water in the oil.
I fitted an engine watchdog on it for better monitoring, and it usually runs around 80 deg but after 60km it ups to nearly 90 deg on 30 degree days.
After stopping the car at the higher temperature, there are no visible leaks or hissing noises. After stopping and turning the engine off there are gurgling noises issuing from the radiator. 20 minutes after stopping, there is still plenty of pressure under the radiator cap, and after taking the cap off carefully, the coolant bubbles and spurts out of the radiator making it look like a green volcano.
My daughters boyfriend added a can of magic fix alloy based head crack/blown gasket repair from Supercheap, but this did not fix anything, not really a big surprise but I have to admit I did fix a cracked head in a Cortina 6cyl many years ago using a repair liquid so go figure.
It may be a toss up between a $450 radiator repair or a $1500 head replacement, but hopefully not both, and to try and minimise the cost, I'd rather fix the correct one first.
So basically, does anyone have the experience to hazard a guess on the cause of the overheating?
Cheers and thanks
Ian

[Trex_s4m1]

I would be taking it to Mazda and get them to tell you exactly. instead of guessing.
could be a cracked hose that leaks once there is pressure, or a faulty radiator cap.. etc etc.. so many things.

[Bird]

Go to a second radiator place and get the gas check in the coolant... if it comes back positive, then go the head.

[Footy Shorts Shane]

I'd spend $15 on a new radiator cap before doing anything else. If it's still the original cap, there's very little chance it's holding the appropriate pressure.
Not saying that's your problem, as it's a tad tricky to diagnose over a keyboard But, no cooling system will operate correctly without the required pressure.

Shane.

[RebsWA]

If exhaust fumes have been detected in the coolant then you have an engine problem.
A simple pressure test at a radiator place or workshop should identify any external coolant leak.

[jwb]

most workshops will have a gadget to check the coolant for exhaust contamination.
this & a pressure test should just about confirm what's going wrong

[dazzler]

Head gasket or crack in head.  BUT : I would pull the radiator and have it pressure tested first.  There is always a reason for everheating.  They can also clean and descale it or maybe even replace it.


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[dazzler]

just to expand.  the kicker here is that it is pressurising beyond the simple pressure from expanding water under temperature.  Keep in mind that the coolant system only pressurises due to it being a closed system and heat expands the water and hence the pressure.  So additional pressure comes from compression escaping into the coolant system.  This can only come from a cracked head gasket or crack in the head.

Sometimes the crack will only 'function' once at operating temperature.

You should be able to pull up with a hot engine.  Crack the radiator cap (be careful) so that it goes to the first release bit but cannot be taken off.  Pressure should release like a soft drink bottle.  Nothing should come out.  What you describe is pressure due to combustion gases. 


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[cp]

Any dampness in the front footwells? Check for signs that your not loosing coolant in via the heating system under your dash.

[noel_w]

just to expand.
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Love ya pun there dazzler.


From past experience I think dazzler is on the money.

[dazzler]

Love ya pun there dazzler.


From past experience I think dazzler is on the money.

PMSL.  Didnt even think that when I posted.  Thanks for making my day!


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[dazzler]

Love ya pun there dazzler.


From past experience I think dazzler is on the money.

PMSL.  Didnt even think that when I posted.  Thanks for making my day!


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[duggie]

: Hi terravista,

By the symptoms that you have described, my guess is either, Cracked Head, Blown Head Gasket or a leak through an Internal Welsh Plug.

I agree with other comments about getting another radiator gas test done and even to the point of the replacement radiator cap. But another test I would be getting done would be a compression test.

my two bobs worth, and two bob aint much now days

cheers duggie

[Mallory Black]

Am I right to assume that the engine is using coolant and not pushing it out?
If that's the case then the radiator and cap can't be suspect because you would either see a leak from the radiator or the coolant reserve tank will be overflowing. And we can rule out a leak from the heater core because you would really smell coolant in the ventilation system.

There's all kinds of tests that can detect if combustion gasses are in the coolant, but they all rely on detection of hydrocarbons (in combustion gases) so that brings us to head gasket as the most obvious suspect and a crack in the head round the combuston chamber or exhaust port as the second.

An engine can still run nice and smooth in the early stages of a head gasket leaking.

Even it's confirmed that the head is the culprit you need to check the rest of the car.

Seeing as it's an automatic, still check that coolant is not escaping into the trans oil cooler that lives in the radiator (I've seen this especially on Saabs)
and also check the engine oil for contamination, the oil on the dipstick should look, well, oily, and not have any kind of milky discoloration, likewise another spot to look is the oil filler cap, if it has the 'coffee cream' look on the inside.

As for causes, these things happen because of:

• Overheating due to faulty thermostat/blocked radiator/ non working thermo fan/aircon assist fan or combination of them.
  Corrosion

to poor servicing in the past or someone could have combined incompatible coolants at one stage and if that's happened the coolant becomes almost like acid and will eat things out from the inside. starting with the head gasket.

Check all these things out as well as....

If the top tank of the radiator is not shiny black and has any discolouration in the plastic it's a sure sign of continual hot running but rule of thumb, if a modern plastic/aluminium radiator is coming up to 10 years old I will be suspicious of it lasting much longer and I usually just replace it as a precaution. Some brands are better than others but the 10 years is about the average.
I didn't mention the water pump and as long as it's not noisy it is OK but.. if the car is apart for a fair while then the seal at the water pump bearing risks drying out and maybe leaking later on, which can be a real pain on a car like that.

see how you go, these are the logical steps but it's important to check them all out     
 

[terravista]

Many thanks for the input people.

Samianderson: There is no Mazda dealer within an hours drive, and they want the car left for a day which isn't possible until the school holiday.

lost, will do.

Footyshorts: the cap seems OK, the spring has same tension as others and the seal is fine but I will double check.

dazzler: sounds more feasible. Would this mean the further the drive the more pressure would build up? The radiator cap has a 13lb release. Wouldn't the pressure build up from exhaust gases result in the cap spring retracting so excess coolant enters the overflow bottle? That is not happening at the moment.

CP: there is no dampness in the footwell. The only time the heater is on is when the car starts overheating and she turns the heater on to use more water in the cooling system.

mallory black: thanks for the thorough reply. There are no visible leaks anywhere. Definitely no oil/water mixing indication. The radiator does not appear to be blocked but that is based on removing the drain plug and running water through the radiator. The thermo fan cut in properly. The servicing has been maintained, but cross coolants could have occurred. The radiator top tank is nice and shiny black. The water pump is quiet. I am not overly technical and don't what an internal welsh plug is. External ones seem fine, no leaks while hot and idling. Any ideas on what symptoms a faulty internal one have?

With what is not really a heavy coolant loss, about one litre every 300km or so should I expect to see steam or water droplets exiting the exhaust? My old Cortina used to look like a steam cleaner, but it would run rough after 10 minutes and go through the radiator volume in a half hour.

Thanks, and keep the suggestions coming please

PS, Any thoughts on a fair price to (1)  replace the head gasket,  and (2) fix and replace t

[Footy Shorts Shane]

Where are you adding the water too? Radiator or recovery tank?

Shane.

[Mallory Black]

Hi Terravista
you'e only see significant water/steam if the head gasket was well and truly blown.
Remember a by-product of the combustion process is actually water

[dazzler]

dazzler: sounds more feasible. Would this mean the further the drive the more pressure would build up? The radiator cap has a 13lb release. Wouldn't the pressure build up from exhaust gases result in the cap spring retracting so excess coolant enters the overflow bottle? That is not happening at the moment.

yes, no or maybe. 

No need to go to a dealer for this.  Just a mechanic you can trust.  You can chase your tail on these things and end up costing you more in the long run with lots of tests.  If a mate came to me with what you have described I would whip the head off have a look.  9 times out of 10 the head gasket will show the problem.  The other 1 out of 10 is to send the head off for prostate exam and a shave if alls good.  New head gasket, new timing belt, new fan belts and thermostat.  fill her up with the correct coolant and test drive.

Best of luck.  You may have mentioned this but where are you?


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[achjimmy]

Have you noticed water coming out of the exhaust?  Put you hand over it at start up and after a while and see if your getting moisture it is sometimes evident. The head is the most likely culprit. Word of warning if it's pulling it into the combustion chamber and burning it up it, prolonged leaking causes electrolysis around the valve seats leading to the head being U/S or ultimately to catastrophic failure when she drops a valve seat.

[terravista]

More thanks people

I can put my hand over the exhaust for 30 seconds, and there is no signs of any more moisture than our 4x4 shows, and it doesn't use any water. Fuel.... yes, and heaps of it, but green stuff.

My daughter is over an hour from us (Waterford West near Beenleigh) and has been there a year and has not had any need to go to a mechanic, so unfortunately there is no local mechanic she has built up any trust with.

We have been replacing the coolant straight to the radiator because that's what is being opened to check the level. I understand that cold filling should result in expansion filling the overflow tank, but that doesn't seem to happen. Is the radiator the right place to add it to?

If the head is cracked or the gasket stuffed, is it likely to worsen with light use for a couple of weeks, or would close monitoring of the Engine Watchdog and top ups every couple of days make the car usable until a full check over and repairs?
Cheers
Ian

[Footy Shorts Shane]

I'd be replacing the cap, but that's just me 

Shane.

[Ynot]

just to expand.  the kicker here is that it is pressurising beyond the simple pressure from expanding water under temperature.  Keep in mind that the coolant system only pressurises due to it being a closed system and heat expands the water and hence the pressure.  So additional pressure comes from compression escaping into the coolant system.  This can only come from a cracked head gasket or crack in the head.

Sometimes the crack will only 'function' once at operating temperature.

You should be able to pull up with a hot engine.  Crack the radiator cap (be careful) so that it goes to the first release bit but cannot be taken off.  Pressure should release like a soft drink bottle.  Nothing should come out.  What you describe is pressure due to combustion gases. 


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When you get to the part with the cap removed, if you give it a little rev you should see it draw down into the radiator if all good. If it comes up our bubbles out it can show a head problem.
As FSS said, start with the radiator cap as you would be surprised how often this is the culprit despite their appearance.
Given the chemical test has shown exhaust you may not be so lucky.
Cheers


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[dazzler]

good point on the cap. you would replace it anyway if anything major is done. 


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[dazzler]

There is no change to smooth engine running as often happens with a cracked head.


There is no oil in the water or water in the oil.

It will only run rough if the crack or head gasket blow is between two cylinders.

There will only be oil contamination if the leak is to an area where oil is, like an oil gallery or in the top of the head.

I once had a holden shuttle that behaved perfectly but used water.  There was a pinhole in the casting into the exhaust chamber near the valve.  It was tiny but enough to leak and vaporise.


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[achjimmy]

If the head is cracked or the gasket stuffed, is it likely to worsen with light use for a couple of weeks, or would close monitoring of the Engine Watchdog and top ups every couple of days make the car usable until a full check over and repairs?
Cheers
Ian

As above if it's into the combustion chamber it's probably doing damage and can get worse. You mentioned BF has used gunk. Was it a quality product or some cheap sh1+ ? As above give the cap a go it's going to cost you $10-20 . Then I would be using two tins of bars leak as per instructions.

There used be this stuff, it was like a block of charcoal the size of a small fire lighter and engine reconditioners used to slip a piece behind the welsh plugs before knocking them in during a rebuild. The stuff was awesome and I seen it seal up a major gasket leak on a four runner head gasket. It's never long term but can buy you a month or two to either arrange a fix or trade ;-)