Indi, everything john has said is spot on! first question.... have you recently acquired the car or is it a long term ownership car that has just started doing this.
Flushing... not just a water flush but a chemical flush is needed. You'd be surprised how much gunk will be sticking around in the pipework and galleries of the engine, Your car is 30 years old and as Mr. Harris said things do tend to get neglected on cars that don't do many miles! First I would dump whatever coolant you have in there and fill with water and Prestone coolant flush (one litre) and fill with water. there are all sorts of advice here but I would do it for a weekend, start Friday night or Saturday morning and fill the system with the solution. Run the car stationary for about an hour at operating temp then if it doesn't show any leaks go for a blast for an hour, repeat the next day. When the engine has cooled down drain out the system and stand back in shock at the crap that is coming out and the colour. Now repeat with plain water, a stationary run is fine for that and id suggest that about three goes with plain water will be required. When you are happy I would remove the thermostat and using a hose flush the rad both ways and the block too. When all is to your satisfaction fit a new stat inspect the hoses and refill the system using the correct anti-freeze and distilled water. Important to use distilled water but more so in a hard water area, Don't worry about that though when flushing as like a kettle in hard water it takes a while to build scale!
Opie oils stock the correct anti-freeze and distilled water, post free it will cost roughly £70 delivered to your door.
On a standard cooking engine I don't believe a stat of 85' or 90' will make much difference if all is working correctly. The only other thing you may have to investigate at this stage is the water pump. Some have plastic impellers and they can self destroy as they get older or even gum up around the blades and the pump is then just cavitating and not assisting the flow around the system. Oh! just one thing more, if on the initial drain its very mucky just do one quick flush before introducing the chemical flush mix as you want the chemical to work on the stuck grime and not on the stuff in free suspension which has been left behind. Best of luck!
Last edited by sewin; 30/08/25 11:01 AM.
