Recent posts by RicardoM in the 'common issues and solutions' thread on cooling system problems are a timely addition...

 

In the last few days my 1.3 Mpi has had an interior heater problem with the temperature varying between stone cold and hot (all of it's own accord). The interior facia temp control has felt stiff sometimes and jams, but with a bit of pressure clicks past the 'obstruction' and resumes normal operation, so I thought nothing of it. I've had it in mind to get into that assembly to sort it, but suddenly the problem has got much worse.

 

On lifting the bonnet yesterday I noticed the coolant was down to the low level mark and there was evidence of leakage at the expansion tank. With a top-up and a wipe clean I fired the car up:

 

The heater temp was still sporadic and once warmed up I checked the hoses in the engine bay; all were warming up nicely and the top hose from radiator to thermostat housing was easily squeezed, therefore I assume that coolant flow is fine, the heater matrix is not blocked and the thermostat is likely to be working well, and there is no evidence of leaks anywhere except the expansion tank cap.

 

Driving today however, the heater temp not only fluctuates but is reacting strongly to engine rev levels (speeding up and slowing down with throttle speed). The temperature gauge is also fluctuating as well, rising (only once thankfully) right up near the red before dropping steadily to about 70, then half-way, then down, then up and so on...

 

On stopping the car and raising the bonnet, the expansion tank cap was hissing and there was quite a lot of coolant sprayed around the engine bay in that area. The tank level eventually settled to the minimum mark. I'm thinking there could be air in the system or the temp sensor may be faulty, but am concerned about the head gasket. What do you guys think?

 

I'll have to get the spanners out now for a bit of tinkering, but in the meantime, any thoughts, ideas, suggestions etc much appreciated.

 

The first thing I would check is the integrity of the heater control mechanism. From your description it looks like something is stuck or broken and heat regulation flaps are disconnected. You need to extract the heater matrix first then remove the dash heater knobs and finally extract the heater / blower assembly through the engine bay.
 
The next thing to do is to bleed the cooling system from any trapped air.
 
One other thing that should help is a cooling system pressure test at 1.1 bar. Let me know if you need help on how to do that.
 
You mentioned an erratic behavior of the temperature gauge. How fast is the needle moving from low to high and back? In seconds?
 
Other than coolant spilling out the expansion tank are there any other signs that may indicate a head gasket failure? See my post here

"The expansion tank cap was hissing". If that's a pressure cap (like a radiator cap but on the expansion bottle, not the radiator) then that could explain all the symptoms.

 ...that could explain all the symptoms.

What do you mean?

What do you mean?

Sorry, nearly all the symptoms. It doesn't explain the mechanical problem with the heater controls.

 

The temperature variations (gauge and heater), coolant loss etc are all consistent with a loss of pressure in the cooling system. There are a number of reasons why this can happen, and I agree with your #2 about most of them. I've also seen it happen on a number of cars where the only actual fault was that either the gasket or the spring (where applicable) on the pressure cap was no longer sealing properly.

Okay folks,

 

I thought I had it fixed this problem as I used the car yesterday and last night with no problems at all. Today though, it's back to an erratic heater temperature and coolant leakage from the expansion tank. A new temp sensor seems to have cured the wild movements of the temp gauge needle and I fitted a new radiator fan switch for good measure. The old one was found to have actually worked a bit loose, but there didn't seem to be leakage from it. Also the heater is back to reacting strongly to engine revs.

 

Whilst driving, it takes about fifteen minutes for the temp gauge to reach 95°C, then about 20 secs to drop to a (now) fairly steady 65 - 70°C and doesn't really go over 75°C after that.

 

Stationary, this is how it behaves from cold: 

 

0°C - 70°C - (15 minutes)

70°C - 80°C - (4 mins)

80°C - 90°C - (3 mins)

90°C - 100°C - (7 mins)

At about 102/ 103°C- Radiator fan kicks in and runs for 2 minutes until gauge needle drops to about 93°C.

 

I've done the one minute running from cold to check expansion tank pressure and it let out a short, soft 'pssst', but it always seems to hiss after running. Can't see evidence of oil deposits on the coolant surface, or emulsified oil on the engine filler cap and the engine oil level is fine as well.

 

To Ken O'Neill: I have a new expansion tank cap on it's way, hopefully that'll cure it.

 

To RicardoM: yes, I am interested in knowing how to check the cooling system pressure, and also how to remove the dash heater controls if possible.

 

Thanks for the replies, I'll keep you all posted.

To RicardoM: yes, I am interested in knowing how to check the cooling system pressure, and also how to remove the dash heater controls if possible.

With engine cold, the cooling system needs to be pressurized at 1.1 bar precisely and see if it holds the pressure. In order to do that, you need an adapter made from a tire valve from a truck and a rubber disc (see photos). The valve will be attached to the cap of expansion tank. When the nut is tightened, the rubber gets squeezed and expands sealing the valve inside the neck of expansion tank. You can use a hand pump or a foot pump with manometer to build the pressure. Avoid using compressed air from a tank! You risk creating a leak if test pressure is too high.

 

 

 

A few words about the time to reach 90 C from cold.

I made quite a few measurements on a fleet of 6 well maintained Felicia 1.3. Here is the average of my measurements:

 

Outside temperature: 10 C. Engine cold.

 

Car stationary: 12 minutes 15 seconds

Car driving in town: 6 minutes 30 seconds (roughly after 6 km trip)

 

If it takes longer to reach 90 C, most often the thermostat is not sealing perfectly when it is closed. You can verify that easily by touching the big hose that goes from thermostat to radiator. The hose must be cold up to 82 C when the thermostat starts to open. It is accepted the hose is slightly warm only in the vicinity of the thermostat due to heat conduction.

 

Other than that, your cooling system is either not tight and/or there is air trapped in it.

Edited 10 December, 201510 yr by RicardoM

Does anybody know what thermostats were used by Jorily in their modified (circlip type) housing for the 1.3 MPi?

 

My thermostat does need renewal, but I cannot get a match for the one I have anywhere here in Galway. It’s brass and is smaller than that used for the standard housing.

 

Dimensions are: 46mm Max diameter, 42.5mm o/a height, 23 high under the flange.

 

Markings are:

 

METAL – INCAR   MADE IN POLAND

13620001 11C 88°C

 

Any ideas what other cars used a similar type or a suitable part number etc?

That particular thermostat produced by METAL – INCAR from Poland (internal code 13.6200.01) included the housing. You can't find just the thermostat. The item is used only in Skoda Felicia with engines 135 B/M/L, 136 B/M, AMJ, AMG, AMH.

 

The OEM part number is 047121111D or 047121111E in case you want to buy one on eBay.