Airlock after new radiator?

[phibbzy]

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...

:censored::confused::confused:

[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.

[phibbzy]

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 :confused::confused: 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]

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]

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]

Poor Earthing will cause these exact symptoms...

jc

[phibbzy]

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]

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]

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


JC

[phibbzy]

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.

[justinc]

a quick check would be to run a jumper lead from the battery neg post to one of the bolts holding the seat frame to the seat box or any good earth on the body, see if that helps?

JC

[phibbzy]

Yes thats what I'll be doing tomorrow. Best not **** off the neighbors at this time of night.

[phibbzy]

I appear to have a resolution on this.

Engine requires a high flow thermostat, the two units in it/installed were not, I guess... - which explains over temping with it in but running okay without...

Also at normal running temp the gauge is now wanting to read at 3/4 instead if its normal 7/16th position (just before half)... This is fine however, since I have a nice brand spanky VDO water temp gauge here with sender to go in on Sunday as well as a raft of other electrical items to go in. I have also decided to get the factory earth points checked, just for good measure as advised by you guys.

A new high temp thermostat has been installed and mechanic has confirmed its running at a normal temp so back to my place she comes and the fun continues...

Thanks all for the help. :D

[phibbzy]

https://www.aulro.com/afvb/images/imported/2013/11/31.jpg

This ain't reassuring haha. Car temp otherwise normal...

[Don 130]

When I had an overheating problem, I read somewhere, that if the 300 tdi engine was run without the thermostat, the coolant would not be held at the back of the engine and risk head gasket failure. I've never had this independently confirmed, but when the wrong (mislabelled) thermostat was fitted to mine, the head gasket blew. A cylinder leakage test may be in order of yours if anything else points in that direction.

[redrovertdi]

https://www.aulro.com/afvb/images/imported/2013/11/31.jpg

This ain't reassuring haha. Car temp otherwise normal...


Mine did that to and the fuel gauge was going up and down with the brake pedal, the cause was two small earth wires on the transfer case top on the drivers side that i had forgotten to reinstall

[phibbzy]

I'll be checking the earth issue tomorrow morning, will advise if I find anything amiss.

[phibbzy]

Hey guys,

Yes there was a broken earth cable running from those the gauges to the firewall. The near full tank I had thought I had turned out to be a few Liters of empty :D:D

It's still getting replaced with a VDO gauge tomorrow!

[Don 130]

Here's hoping your troubles will be over when it's all fitted.

[Jode]

And you might want to buy some diesel....