Overheating issues

[laurenceyon]

Hi All, I hope you can help!

My 16V is overheating. I've owned Mk2's for 10 years now so I know my way around the engines, I would just like some hints and tips from yourselves to primarily save time over the weekend when I carry out the fix. Firstly, I don't think it's the head gasket, why? because the oil hasn't mixed with the water and the temperature goes to 3/4 - no higher.

The symptoms
- no heat/very little heat from the heater matrix.
- the water thermometer rises to 3/4 and dumps the water/steams
- the fan intermittently kicks in - it kicked in 30 seconds after switching the engine off the other day however, it did not kick in this evening or did i notice it kick in throughout the whole 10 mile trip I have just taken her on.
- The temperature of the water does not drop from 3/4 when cruising - I've just taken her from a spin on the dual carriage way and it didn't go down.
- no loss of power, no funny noises apart from squeaky auxiliary belts

i've already thought that it might be: 1. Water Pump 2. Thermostat 3. Blocked heater Matrix

She is a 1990 K-Jet 1.8 16V - it's a smashing little engine and i'd rather salvage it than replace it.

Many thanks in advance

[X4MGS]

Do you still have the valves fitted just before the pipes enter the matrix (engine side)?


Does the coolant bottle have a black cap or blue?


Do all the pipes from the water pump get warm when up to temp?



Have you tried a new thermostat?


Is your passenger side footwell damp?

[laurenceyon]

The cap is black and it has had the heater matrix recall modification, i'll have the answers to the rest of the questions on Saturday if I haven't fixed it already.

What the difference between the blue and black cap anyway, other than they're newer?

Thanks

[Mr Blue]

As above and check the radiator for small leaks at the bottom front.
Had the exact problem with a radiator leak and I kept topping up with water on long trips. The water just boiled over and caused the system to pressurise out of the water bottle.

Fix all leaks, fit a new fan switch, flush the radiator, the matrix and top up with 50/50 pink coolant.

Must fit that blue coolant cap and check it has rubber o ring.

Bin those recall heater valves in the engine bay. Some 22mm copper pipe and some jubilee clips to bypass them.

I had the black cap fitted and over pressurised the system which it burst one of my core plugs 

[X4MGS]

The cap is black and it has had the heater matrix recall modification, i'll have the answers to the rest of the questions on Saturday if I haven't fixed it already.

What the difference between the blue and black cap anyway, other than they're newer?

Thanks

All I know is the black caps fail and the blue ones don't...

I had a similar situation with the wife's MK2 and I Fitted a Genuine blue cap and it sorted the problem.

Like Mr Blue also said get rid of the valves - I would suggest getting proper hoses rather than the copper pipes - but as a "quick fix and test" that's a good solution...

But you still need to check the rest of my list to maybe find the true issue...

[leigh_harty]

Do you still have the valves fitted just before the pipes enter the matrix (engine side)?


Does the coolant bottle have a black cap or blue?


Do all the pipes from the water pump get warm when up to temp?



Have you tried a new thermostat?


Is your passenger side footwell damp?

Does the same apply to a corrado 2.0 16v 9a engine?

Just fitted a new waterpump and thermostat and im getting the 3/4 temp then bubbling out... no heaters and fan isnt kicking in

[Thom89]

Sounds like head gasket to me, but if all the above fail, and before your take the head off, try removing the water pump, and check that the impeller has not corroded away! Ive seen this a few times over many years, when non OE pumps have been fitted in the past... Fit a new pump as a matter of course, and also a new thermostat.

Thom