Airlock after new radiator?

**phibbzy** · 26th November 2013, 09:07 PM

Hi all, my 95 'fender has been off the road for a month or so undergoing a string of much needed improvements & repairs. One of which was a new radiator as the original one had met its maker and had fins falling out all over the show.

Unfortunately I didn't find out it needed a new radiator until I had pulled it out (I was just going to clean the ruddy thing, not blow a hole in it) so it's been sitting up for a few weeks without coolant but with all hoses covered up with plastic.

I've fitted everything back up tonight and everything was going good until I noticed at idle the temp was marginally higher than normal and would peak over the apex of the gauge.

I filled it by trickling coolant into the expansion tank and I'm guessing i've caused an air lock (this is what being excited to test your new intercooler gets you!).

The thermostat housing is hot and so is the hose that leads to the rad. The inlet area around the top of the radiator is hottish/warm and quickly fades to cold on the rest of the radiator. There does not appear to be any circulation at all. From the thermostat plug I can see the thermostat opened (I believe anyway) but no circulation through it. The heater is pouring out nice warm air as well. I've tried for the last few hours to bleed it out of various places but it would appear still locked, including the coke bottle thing.

A short test drive (up and down the street) resulted in it temping up to around 3/4...

**jboot51** · 27th November 2013, 05:20 AM

Thermostat may be stuck closed or the plastic 3 way connector near the ac compressor is blocked ( ejector ?).
With the ejector working there is constant flow from the thermostat housing and top of radiator , to the expansion tank. Even with the thermostat closed the water in the expansion tank will heat up due to this flow of water. The ejector is there to take any air in the system and deposit it into the expansion tank.

**phibbzy** · 27th November 2013, 05:12 PM

Originally Posted by jboot51

Thermostat may be stuck closed or the plastic 3 way connector near the ac compressor is blocked ( ejector ?).
With the ejector working there is constant flow from the thermostat housing and top of radiator , to the expansion tank. Even with the thermostat closed the water in the expansion tank will heat up due to this flow of water. The ejector is there to take any air in the system and deposit it into the expansion tank.

Confirmed the 3 way thingo is clear and okay.

I took the thermostat out and tested it. It would not open in boiling water...

I changed the thermostat for a new one but the same thing occurred.

Probably important to note that the engine is overheating on idle...

When I took the thermostat out and ran with nothing it is now running fine

gets up to temp (just before middle) and sticks there without worry. I took it for a good thrash around the hilly streets of the area and it behaved fine! The radiator is evenly warm and everything seems to be humming away.

Could it be the water pump not having enough guff to push the coolant around? I note that there is not a lot of pressure build up in the header tank even after my thrash about...

**jboot51** · 27th November 2013, 06:01 PM

mmmmm......

Something doesn't sound right.

Test the new thermostat in boiling water to make sure its not a dud.

The spring and stuff on the thermostat fits into the housing with the smaller dome side facing outwards.

There should be a small hole on the edge of the thermostat with a jiggly bit, this needs to be at the top.

When refilling you need to bleed at the radiator first and then the thermostat housing.

Unlikely to be the water pump, the front seal usually fails, long before they wear out.

**phibbzy** · 27th November 2013, 06:44 PM

Yep, tested both thermostats and they both open in boiling water. The old one did not open at first but after I pulled it open manually it seems to be functioning normal.. Perhaps rusted/fused closed from sitting out?

Also confirmed the thermostat is in correctly. At the moment, there is no thermostat in it which allows me to drive it lightly...

I suppose another thing to add is I have physically moved the temp gauge in the dash over to install a tacho. I have also unplugged and plugged back in the sender unit plug (have not touched the sender itself).

I really cant think of anything else...

**justinc** · 27th November 2013, 06:52 PM

Poor Earthing will cause these exact symptoms...

jc

**phibbzy** · 27th November 2013, 07:00 PM

Originally Posted by justinc

Poor Earthing will cause these exact symptoms...

jc

Cheers JC, can you elaborate a little? Poor earthing on the battery? The sender or temp gauge?

**jboot51** · 27th November 2013, 08:02 PM

There is the main earth at the gearbox on passengers side, goes from the battery via the chassis then gearbox. If this was faulty you would notice when trying to do a cold start, starter motor will struggle.

The earth for the instrument cluster seems to end at a lug/stud on the firewall, in the engine bay on the drivers side.

Easiest way to diagnose these is to use a set of jumper leads from the negative on the battery to the engine block and then bulkhead, see if it makes a difference.
The gauge will be using the firewall earth, while the sender will be using the gearbox earth.

**justinc** · 27th November 2013, 08:06 PM

As above, sorry was away from the 'puter for a bit^^

JC

**phibbzy** · 27th November 2013, 08:31 PM

Alright well that will be my focus tomorrow then.

I've had the batteries out recently and there is an older battery sitting in it for the moment while I rig up some stuff to hold the batteries down. Perhaps the battery has a bad earth post? In any case, we'll see how we go tomorrow.

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