Coolant Level Dropping
 

Hello and please may I ask everyone's advice

I'm new to the K-series engine having recently come back into 75 ownership after a series of 75 diesels long ago. Almost immediately I'm having to top up the coolant after every trip in my 55 reg 1.8t. Just 50-100mls each time. The car had a new head gasket some 3k miles ago before I bought it and the inlet manifold gasket was done then. I've put a new gold resistor on the 2-speed fan, which is cutting in at around 105c. The engine runs at a steady 96 on the motorway. No mayo in the filler cap, oil levels steady and clean.

I'm guessing from reading posts here that it is most probably a leak somewhere in the coolant system. In fact there are so many posts and possibilities I confess to being a bit confused as to where to start! I would like to eliminate possibilities one by one and so starting with the simplest first I replaced the rad expansion cap. No improvement, it needed 100ml today after just 7 miles.

What should a not especially mechanical person like me do next?

thank you
Dave

If it's an external leak then the anti-freeze as it dries off will leave a tell tale stain. A torch and one of those mirrors on a stick might help if that's what you have.---;)

Firstly ensure its bled correctly before looking for any leaks.

when I first got my 1.8 turbo I made the common mistake of assuming the level of coolant in the header tank should be to the top of the fins, I topped up and wondered why it kept dropping to about 15 mm below that. thereafter it maintained that level. Being a bit short of the little grey cells this went on for several months till I cottoned on.

Interesting point about the fins. I have been topping so that I can just see the "MAX" mark. But the level has been dropping just out of sight below the min. There seems to be a small volume between max and min.

I have looked for obvious leaks and there's no sign of any pink stains. Nothing on the drive either.

One of, if not the most common places this engine leaks coolant is from the plastic T-piece in the main hose going from the head and across to the radiator top connector. Check for wet/stain on the hose that drops down from the T-piece behind the radiator to the thermostat (PRT).


TC

As an owner of a Turbo if i have coolant loss and assuming no airlocks ie recent coolant change its best i think to get her up on a ramp and run the engine to see where any coolant is escaping from. In 7 years i have had to do this twice.

First time it was the IMG that was weeping - took an hour to show up on the ramp- obviously heat effect on the gasket causing some expansion -with a plastic manifold its propensity to warp makes this a classic leak point. Since then i have swopped the plastic manifold for a metal one.

Second time it was spotted after a few minutes - the clip on the small hose from the front coolant t-piece was loose .:shrug:

It could be a number of things, but firstly I’d check the oil level on the dipstick. If that isn’t rising or changing colour, inspect the inlet manifold gasket. Feel all along the manifold where it’s in contact with the head.

In my experience the inlet manifold usually leaks when the engine is cooling down.

After that have a good look at the radiator and all coolant hoses and connections, particularly T pieces. Look for any coolant stains on all of the above.

Depending on what type your head gasket is, if it’s had an MLS fitted look at where the head meets the block under the exhaust manifold at the drivers side front of the engine. It’s a common failure point for faulty MLS gaskets to externally leak coolant here. It’s easy to see if it is leaking.

Check around the water pump, this can leak but evaporate off very quickly making it hard to trace.

Don’t forget to check the coolant hose on your turbo either as this can also leak this usually leaves a pinky orange stain on the subframe directly beneath it.

Also is your expansion tank cap in good working order? It’s possible it may be allowing your coolant to evaporate when under pressure.

The 90deg elbow at the top of the radiator is another weak spot (one of many!). Fortunately it's an easy leak to spot and easy to repair.

I had a similar sounding problem with my 1.8 K series coupe a few years ago There was never any puddles under the car, but I was loosing coolant somewhere. In the end I found the thermostat o-rings were the culprit, so check the back of the engine behind the water pump.

Weird how it's exactly the same part (CDU3858) that gives me grief on my ZT 190 these days. :shrug: