heating and running issues

[mk2gtimatt]

i have an 8v gti pb engine on a j plate.
sometimes its a bit sluggish to start, and once warm when i come to idle, the revs are erratic, sometimes idling about 1000-1400rpm, sometimes they drop and 'bounce' between about 700 and 1500rpm. we put a different engine in, but the old one did the same (turned out to have a cracked manifold!) so not sure what this could be. this one looked like it had a new idle control valve so dont think its that. possibly timing?? something sticking??

also, i seem to have a coolant leak, hopefully not from the headgasket, but it seems to be coming from this area, near where the cooland pipe goes into a plastic water jacket on the nearside of the engine. have replaced this, but it still seems to be here. also, i have no interior heat, i have a new heater matrix (genuine) and ever since put this in have had no heat. had to replace it cos the old one exploded! so not sure if something else has happened here. the temp gauge doesnt quite go up to the first white line. thermostat stuck open??? and finally, as i have a leak somewhere, the coolant light comes on now and again, so i top it up, but yesterday i went to top it up and it boiled right up, loads boiled out of the header tank, had to put a good litre or two back in. the heater matrix pipes seemed hot, the top radiator hose was vaguely warm and bottom hose was cold.
please help!!! :embarassed:

have had one suggestion of water pump failure???

[Mr Blue]

The plastic flanges on the head always crack and leak water. Did you use a new O ring? I had to use some sealant and gasket paper for a good seal.

Take off both pipes that go into the heater matrix and run water (hose pipe) through one of the matrix pipes till you get a nice flow of water out the other end. Reconnect and then bleed the whole coolant system again

Also is your radiator genuine? I had the same interior heating problem for nearly 2 years till i changed my radiator for a genuine one.

[mk2gtimatt]

what plastic flanges on the head! and a new o-ring on where? it was ages ago we put a new heater rad in so i cant remember! both the pipes that go to and from the heater matrix were hot so im assuming thats ok - yes it is genuine, and was brand new. ive no idea about the rad tho, not ever changed that. ill have a go at it on sat and report back! thanks for the suggestion tho

[dan23]

the mk2 suffer from heating failer inside the car, most ppl go right for the common things thermastat or heater matrix, but usuail its the valve that lets the hot water into the heater that doesnt work as it has an open valve inside it and this gets stuck shut and wont let the hot water to pass through, therefore meaning you get no hot air. i had the same problem with my golf, and once i free'd up the valve so it would open when it should it was fine.

go to this site and i have done a step by step guid on how to make it work again

http://www.kentmodified.co.uk/forum/viewtopic.php?t=915&postdays=0&postorder=asc&start=140

[mk2gtimatt]

actualy thinking about it, it could b the radiator, as this is the only old part from before i changed the engine. it hadnt had the valve reworking, which is y the first heater rad blew, then when i changed the engine i managed to find some valves, so maybe a new rad would b an idea??? i dunno, im fed up with cars! think ill just get back on my bike!