Why is it still boiling?

I had my thermostat and rad cap replaced the 3 weeks ago (m13a engine) and in the last week my trucks over heated twice. The first time the expansion bottle had fallen off as well, so ive cable tied that to the bracket and it seems not to have moved, but today it boiled again.

It started to get warm this morning on my 15mile drive to work (didn't go above 3/4s on the gauge0 - i slapped the heaters on full bore and it cooled to normal just below half way. Yet this afternoon, without warning, whilst i was watching the gauge it went from normal to red-lined in about 2 secs and then started blowing steam again. I whacked the heaters on full again, but this time it went cold after about 30secs even though it was switched to hot

Ive been back to the garage and my mechanic says, because the rad cap and the thermstat have been changed we can rule them out. But we're unsure of the next thing to check. any suggestion??!!! I'm thinking rad and water pump next and possibly the fan. My mechanic is thinking the same but also the head gasket too :sick: Theres no sign of any oil in the rad or mayo in the oil. So what do people think - whats my next best option

Did you change the thermo and rad cap cos it was overheating or has it only started after? Boiling but cold from heater sounds like it,s not been refilled properly/ airlocked. How does the rad look? Mine used to overheat low range in hilly Forrest , took it out, soaked andhosed it through made a big difference sits just over half now .
John.

Does your model have the electric radiator fans? If so, have you checked that they operate? Just lift the bonnet and let it idle for a while, they should come on fairly quickly and noisy. Also, is the radiator not clogged in the fins? Engine oil full and of the right type?

Are there any leaks, especially under the manifold where there is a steel connector that is prone to rusting out, bugger of a place to get to, at least on the G13BB engine. Connections to the overflow tank tight? Correct radiator cap fitted? I use a 1.1 Bar cap. Even a clogged airfilter will cause heating problems

from experience, little Ooky suffered with a clogged rad on more than one occasion.
after leaving a hose running into it for almost 30 minutes, the amount of fine silt that came out was astonishing.

in the end, I replaced the radiator

what your explaining is EXACTLY what happened to mine down to the expansion bottle falling of its bracket, downsides its the head gasket, i had my head off and then skimmed, new gasket and its been fine ever since

bluejimny wrote: what your explaining is EXACTLY what happened to mine down to the expansion bottle falling of its bracket, downsides its the head gasket, i had my head off and then skimmed, new gasket and its been fine ever since

bit off topic sorry but have you been out in your jimny yet Rus?