Technical mk1 blockage

[danspence13]

My mk1 5 door punto is slowing getting there lowered etc etc however its a 1.1 at mo and I keep getting a blockage somewhere and the heating stops working til it gets rebleed. Where do you think I should start looking for it or could it be something else doing any info or advice would be greatly appreciated

 

[dave]

if headgasket has gone it will keep pushing air into cooling system

 

[fingers99]

Compression test will reveal if the HG has gone. Failing that, you have a leak in the cooling system. Most likely sources of non-obvious leaks are the water pump, water pump rail O ring or the rail itself. Often you can only spot the leaks by running the car up to temperature and crawling underneath.

 

[danspence13]

Ok thank-you I shall take a look tomorrow much appreciated for the replys

 

[Ralf S.]

Air in the system can only come from a head gasket failure.

A leak would just show up as loss of coolant, not air in the system.


Ralf S.

 

[dave]

A leak would just show up as loss of coolant, not air in the system.


Ralf S.

what would be in the place the lost coolant was in after it leaked out?

 

[Ralf S.]

what would be in the place the lost coolant was in after it leaked out?

Coolant that has replaced it (from the header tank).

The cooling system is under pressure (1.2 Bar?), so coolant (and any air in there) can only ever be pushed out.

Only something pressurising air at an even higher pressure (e.g. a piston or combustion pressure, if the head gasket has failed ~ circa 12 Bars) can force gas into the cooling system.


Ralf S.

 

[blu73]

thats not strictly true, although i have read in many places these are meant to be self bleeding engines they could only do that without the cap on.. By your own argument its a pressurized system so where can the air go, it can't just come out or the system wouldn't be holding pressure - the cap will only vent if there is too much pressure. It should self bleed without the cap on but its easier to bleed cold with engine off anyway, and quicker, and you can't just drive about without the cap off either for obvious reasons. If it were true why would there even be any bleed screws......?

Also, i would say 99.9% of the time a HG goes on these as a result of something else and its more likely that a blown HG is a result of another issue (which could be an airlock causing cooling problems), its very rare despite what people say that the HG will go on a FIRE engine unless something causes it too. Heck i've had turbo one do over 60k odd on a stock HG and was still fine when the car was broken up.

 

[fingers99]

Point is, it's only a pressurised system when up to temperature. After that, the pressure decays (which is why when you open the cap on the expansion tank when the engine is cold, you don't get covered in cold water!) -- as it cools, it will suck in air through any leaks.

Simples.

 

[danspence13]

Have been told that i have a snapped bolt on the rockerbox head is causing my pressure loss . Also have had a new rad fitted as mine had a blockage but thankyou for all replys much appriciated if and once bolt has been drilled out and sorted ill get the system pressure tested thankyou again on the advice regards dan

 

[dumbledore]

Head twice issues with the HG on my car but never head problems with the heater. When the HG starts to go air is pushed into the cooling system. The way the coolant moves around the engine results the air to get trapped in the radiator, which in turn causes the coolant level to drop and car starts to overheat. As the heater matrix is located in the entrance of the engine as long as there is enough coolant the matrix will work. In fact when the car overheats is best to let the air flow through the matrix so some cooling is achieved. So is possible the heater matrix to be blocked without HG beeing dead.

 

[fingers99]

Have been told that i have a snapped bolt on the rockerbox head is causing my pressure loss .

This sounds all wrong -- the rocker box/cam cover contains no water.

 

[blu73]

one would hope it doesn't have water in it

 

[tinytim]

This is a leaking head gasket; easy to confirm with a cylinder compression test or just inspect the spark plugs; the plug in the leaking cylinder will have brown deposits on it......