CliffC

My head gasket had failed causing the issues of cycling the heater hot and cold and also after only 2 mins running from cold if I opened the bleed T slowly, coolant would begin to escape. Normally this happens when the coolant is hot but not after 2 mins from cold *nono*There were exhaust gases entering the coolant system and pressurising it.

When you start up,from cold does your coolant system pressure up prior to the temperature rising? If you run your heater does the blower temperature run hot then cold ?

Jonathan Firstly the clues were there but I suppose you always hope it is not the HGF. When Rich came over we took the plugs out and checked them and they all looked Ok. We then stuck this probe camera down the plug hole to see the top of the piston. They all looked dry except the forward facing cylinder. I had also smelt the coolant and though it smelt of exhaust which again Rich agreed with. the garage confirmed the HG had failed very close to the wet looking piston. I had also read somewhere that the most common cause of a heater going hot then cold was down to HGF on a K series. Regards Cliff

final update: It was a HGF located near the front facing cylinder. This has now been replaced with a head skim for good measure. Thanks to all who contributed to the thread and also Rich (Skeetsy) who came round and confirmed it was HGF before it went to the garage for repair I took the opportunity to replace the water pump, cam belt, sump (it had been whacked too many times for comfort) as well so all good now. Regards Cliff

Update: Andrew, thank you for your message. I have today been tinkering with it and i was getting no where. At one point i thought i had cracked it as all seemed to be OK but again the heater went cold and the engine began to overheat. So i checked the oil cap and....... some small amounts of a mayonnaise like substance 😔 ☹️ HGF i suspect. Now this would also point towards the engine running a little rough before the winter hibernation but even then it seemed to running fine most of the time and it did not overheat before the winter break. So that explains why i was unable to get all the air out of the system as i knew i was filling the coolant slowly and doing it correctly. As i said earlier in this thread i thought there was something strange going on. Now, where to get the HG replaced in Dorset/UK South? Any suggestions gratefully received. DVA upgrade time?? Cliff

No water is being lost via the expansion bottle via the cap. When the coolant is hot you can hear the pressure release when you open it. Same with the T piece . The coolant looks the same as it did when it went in. Yes the engine if just left to tick over will take an age to warm up and you can tell the stat is opening as in time the J pipe will begin to warm up as expected. It just seems to get to operating temperature and then for no reason the heater goes cold. So to me it would appear there is an airlock but I cannot believe much if any air was left in when I filled it. Edited by - CliffC on 3 Apr 2014 21:45:09

Update: thanks for all your words of wisdom first and foremost. I emptied all the coolant out again, removed the stat and confirmed the 3mm hole was at the top. I then lifted the rear of the car slightly which made the T piece the highest point. I then began to fill SLOWLY...and I mean slowly. First to go was the radiator overflow ...blocked this off then the header tank came up to the level...put the lid on and carried on filling. Even when the T piece was full I massaged the heater return pipe and lifted the T piece hire with further bubbles still coming from the T piece. I also lowered the car to normal level and was able to get more water in and air out of the T piece. I was convinced I had followed the procedure and had got more coolant in this time than before. Started the engine and went for a drive around the block. Heater was warm but not hot for 10 mins and the car was at 80degrees when all of a sudden the heater goes cold very quickly and the engineer temp begins to rise above 100 😔 So I left it to cool and the T piece was showing empty so again filled and massaged with further bubbles appearing. What I have noticed is if I squeeze the small hose that runs between the lower heater outlet and the stat housing I can hear air bubbles in this pipe. I have not had the big gulps of air appear In the header tank as before neither ☹️ Could the heater have a fault ( there appears to be no leaks though and it does work intermittent) How else can air be getting into the system? What if I shut the heater off and see if engine temp stays at 80? Thanks Cliff

I will give that a check tomorrow and let you know if it was blocked. I am still,getting the odd bubble from the T piece if I massage the hoses and I 'm able to add more coolant every time. The strange thing is I have never had this much problem in the past which would suggest something is up. Thanks for your reply. Cliff

Thanks fro your replies. Update: i emptied the coolant and refilled it this time using the Bleed T piece. i have always used the header tank and lifted the car as high at the front as possible in the past so i thought try the T piece method. I made sure the T Piece was the highest part and began filling slowly...The Header tank got to its level first and then i locked it with the cap. The radiator breather followed shortly afterwards and i blocked that off. i then continued to fill via the T piece until i could get no more in. I massaged the pipes as much as possible during warm up and some bubbles appeared in the header . i had the heater on and this was blowing hot air.. ,,so off i went for a quick drive and after 1/4 mile i notice the heater went cold and the engine began to heat up. Got home OK and waited for it to cool down. T piece was not full so added some more coolant as before until i could get no more in. again some bubbles via the t piece. Went out again and thought i had cracked it (3-4 mile run with no problems then the heater went cold as before) i'm getting there but this is tedious and i have never had this issue before. I will just keep on little by little at a time. Cliff

Ian Ian I have changed the stat and filled the coolant many times without an issue. This time it's a a right bugger....hence the water pump question in case I was overlooking something. I am not losing any coolant and topping up at the bleed t piece but this generally just fills the header tank. I have even lifted the T piece to be the highest point and made sure the coolant is flowing towards the heater. I shall keep on trying the tried and tested methods until I succeed but does anyone else have some tips? Thanks Cliff

Update and thanks for the replies above. I have drilled the hole in the stat and I filled the system slowly and I thought all was good. The heater began to work as normal and I thought that the issue was gone. The temperature began to rise and the fan cut in as expected. But...the heater then went cold so I assume the airlock has some how got back to the heater unit. So after further massaging of the pipes etc and also filling up via the bleed t piece the heater will initially come back but will then go cold again. I have done this thermostat change before and never had this issue with refilling the coolant in the past. Out if interest how would you know if the water pump had failed on a 1.8 K Series? Thanks Cliff

I have replaced the thermostat today as i thought i had a faulty one as the lower hose did not get warm. After checking the stat it appears to be working but i replaced it now so i have a spare. When filling with coolant following all the little tricks about lifting the front of the car etc.. and i have the bleed T piece i began to fill the system slowly. Everything appears OK but during the test blat i noticed the heater was blowing cold air when normally when the temp is up to 80c it blows hot air. Shortly after this i noticed the engine temp going up so i did a quick turn for home before it got too hot. So have i got a air lock in the heater and how do you get rid of it please? i have filled the system with the car running and the heater valve open but still no hot air. thanks Edited by - cliffc on 23 Mar 2014 17:05:12

I think that was us ... We're you in the green seven. We were coming back from Street, Somerset after a bit of shopping. Cliff

Revilla Hi, yes I took the sump, sorry ☹️ Regards Cliff

Mark Brilliant news and thanks. 😬 Johnny - even bigger thanks to you.. *thumbup* 🥰 am back this Sunday and will be in contact. Thanks to all involved and the messages on this thread Cliff