New heads and overheating

MilesnMiles · Post by **MilesnMiles** » Mon Apr 20, 15 6:46 pm

WtF
First test drive with new heads on
10-minutes and the temp guauge is heading to the hot end sharply

I have a small leak at a core plug

Radiator top and bottom hoses hot

Heat from heater hose on the inlet manofold

No heat on the heater hose that goes to the water pump

Heater blows cold and would usually run pretty warm to hot by now.

Please tell me I've not somehow blocked a water way when fitting hard gaskets

Pete · Post by **Pete** » Mon Apr 20, 15 6:58 pm

Air lock?

Reverse fill the system if in doubt.............

latil · Post by **latil** » Mon Apr 20, 15 6:59 pm

Thermostat not fully opening? Try without it.

Mick70RR · Post by **Mick70RR** » Mon Apr 20, 15 8:42 pm

Check the ignition timing is not too retarded. Do you use a vacuum advance? My car runs too hot without a vacuum advance fitted to the dizzy. I've had two of them fail and the first I knew something was wrong was the engine felt down on power and it started running hot in traffic and run on when I turned the ignition off. Replaced the vacuum cans and temperature and drivability was back to normal both times.

MilesnMiles · Post by **MilesnMiles** » Mon Apr 20, 15 9:30 pm

Haven't touched the timing but I did disconnect the heater hose (one of them) I will bypass it and see what follows.
Last time this happened it was indeed a stuck thermostat, but everything was good until I changed the heads.

MilesnMiles · Post by **MilesnMiles** » Mon Apr 20, 15 9:58 pm

Got vac advance Mick, but I really did do just 10 minutes of 30 mph plus standing in idle.
I'm hoon guts an air lock of heater based issue as that is not functioning current
Y and was before i changed the heads.

Cannonball · Post by **Cannonball** » Mon Apr 20, 15 10:29 pm

MilesnMiles wrote:Haven't touched the timing but I did disconnect the heater hose (one of them) I will bypass it and see what follows.
Last time this happened it was indeed a stuck thermostat, but everything was good until I changed the heads.

you can not just blank one heater hose off either loop it or run it,,,,,

MilesnMiles · Post by **MilesnMiles** » Mon Apr 20, 15 10:38 pm

I know Dunc, I have a loop that I use each summer to cut out the heater. I'm hoping it's an air lock plus the coolant was lower than I usually fill it. I will try the loop and cut out the heater tomorrow.
I meant that I disconnected one of the heater hoses when doing the head change and reconnected it before starting the car.

Mossy68 · Post by **Mossy68** » Mon Apr 20, 15 10:48 pm

Does sound like an air lock Miles.
Do you measure your coolant in ?
I changed the coolant in the Jeep when I bought it. They are rebound for air locks. There is a bleed in the thermostat housing , but I didn't risk it !!!
Managed to " burp" it by massaging the hoses. Engine running with rad cap off.

MilesnMiles · Post by **MilesnMiles** » Tue Apr 21, 15 7:53 am

Mossy I'm hoping so, I did just bung coolant in and start it. The fact that the heater is blowing cool maybe a positive indicator of an air lock as it worked fine before the head change. Will report back tonight.

charger01 · Post by **charger01** » Tue Apr 21, 15 9:59 am

Stick the front end up on ramps & leave the rad cap off. Fire it up. Air will always make its way to the highest point.

70_charger · Post by **70_charger** » Tue Apr 21, 15 1:54 pm

Air lock will more than likely be behind the thermostat stopping it reaching temp to open due to no coolant hitting it to warm it up, therefore no heaters, will idle at day long but once driving will overheat. Don't run without a thermostat as water flow needs the thermostat to slow flow down either replace with new or jam open. When I used to rally I would drill 5 holes 1/8th in thermostat flange to allow some coolant flow to lower running temp, irmscher used to sell race thermostat the same for opel manta road race use. You can also get steel rings with different size hole in to run that restrict flow in place of thermostat

MilesnMiles · Post by **MilesnMiles** » Tue Apr 21, 15 3:32 pm

Thanks. I do always drill one 1/8" hole to allow water past the thermostat. If I do run without one the car runs way too cool, below 150 which is not desirable at all.

latil · Post by **latil** » Tue Apr 21, 15 4:00 pm

I meant stat out,round the block and watch temp. Don't run far without it. Could always test it in a saucepan of water when the Mrs is out if you have a thermometer handy.

MilesnMiles · Post by **MilesnMiles** » Tue Apr 21, 15 9:12 pm

Thanks everyone, all fixed now.
I jacked up the front, took the heater hoses off, filled the block via the heater inlet to the water pump and then topped up,the radiator. Went for a 40 minute drive and never saw it over 180.
All good and very relieved