Radiator Expansion Water Tank Cap Compatible for Fiesta Focus C-Max Mondeo

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With the engine cold, I first loosened the cap as much as possible(almost one turn). Then I let it sit in that position for one minute. The I tried to loosen it some more(almost a quarter of a turn). I repeated this step again after one minute untill I made 2 complete turns. Then it started to loosen after each try. Right at the beginning of this thread I suspected CHG failure. I think paul 1963 (post above) is spot on. The symptoms described are a classic example of a tiny defect appearing. Nifty physical test for HG failure. I dunno if that would work with a lower tech pressure gauge (or even an improvised manometer) but it seems a possibility. Difficult bit would be getting a good seal. That'd be a false negative. Probably more likely than a false positive, which would require contamination with coolant or old test fluid

Only reasonably practical desperate improvisation I can think of would be removing the thermostat. This will potentially increase circulation in the cooling circuit, allowing it to remove more heat. That's a very broken car though. Might not be sufficiently sensitive for a marginal integrity loss. If the coolant level is low, add the correct coolant to the reservoir (not the radiator itself). You can use diluted coolant by itself or a 50/50 mixture of concentrated coolant and distilled water. IF the water pump is belt driven, I suppose it might be possible to change the pulley to increase the pumping rate, but I doubt it would be worth the trouble. Further to my last post, the bubbling coolant has continued but in all honesty I am not too fussed as long as the car can last me another 3-4 months. My main concern is that if I drive it without the internal fan on to accommodate for some of the extra heat, the temperature of the engine (on the dashboard, at least) begins to very slowly climb above 90 degrees. It remains on 90 if I keep the fan on, but the engine fan creates a hell of a noise (not that it matters if it is working). Now it is getting towards summer I am starting to get fed up of absolutely roasting in my car every time I go to/from work so am looking for an answer, however, given my problems with previous mechanics and the fact that I have already paid out a few hundred pounds on this issue I wanted to ask the advice of you guys before having a paid mechanic come and look again.

Real MPG

renewed on my diesel car last year and found the reservoir empty when I got home - the techy just hadn't run the engine enough for the thermostat to open fully.

If there was no overheating, the water pump replacement is a bit suspect, but is unlikely to have caused a head gasket failure, which seems to be suspected by the OP. IF your mechanic says he has done that test (its a chemical test kit) and you believe him, that seems to be that, unless that kit does false positives, which AFAIK it doesn't.I wouldn't do that, and I probably wouldn't buy the kit they use, but it should be possible to adapt another form of pump. I suppose I could mist water into the air intake to slightly reduce the risk but there's a bit too much happening as it is.

Coolant also helps keep your engine working as efficiently as possible, helps keep its emissions low, and even helps provide that toasty heater air on cold days. Open the hood and locate the engine coolant reservoir. It is often a translucent white color, and has hose(s) connecting it to the radiator. Its not really a compression tester as the term is usually used. Its testing for radiator pressurisation, with a FSD of 5 psi, so it'd be more sensitive to damage than a compression test, but perhaps still not sensitive enough. unclip the two upper hoses by hand, unclip tank from the holding plates, drain in jar through the openings where you unclipped the houses, use the pliers to unclamp the main hose, pull the tank away from the hose. Install the new tank.I try and be as cynical about garages as the next man, (though/so/because I have hardly ever used them apart from MOT's) BUT I think the innocent-until-serious-grounds-for-suspicion principle ought to be applied. The OP is unlikely to want to bother with that though, especially as he already has some blowing from the coolant reservoir so couldn’t easily detect any local boiling due to modification. Agree with the screw into it, if you used a really sharp self tapper, you might get away without drilling a pilot hole and dropping bits of metal into the tank. I've had 2 or 3 serious overheating incidents due to failed repairs on the fan control circuit, so I'm expecting a head gasket failure. Correct antifreeze mixture? off the shelf antifreeze is pre mixed isnt it? https://www.eurocarparts.com/p/triple-qx-red-ready-mixed-antifreeze-coolant-5ltr-523770511