Red light of doom

[andygriffiths]

After getting the van running on all 4, she has now lured me into fixing that "red flashing light"

(It's a T25 1.9 petrol watercooled with carb)

I'll try and give you the whole story;
Originally it went into the garage (yes, the same one that said it had dropped a valve - but it hadn't) to get the heater working shortly after she purchased it about a month ago.
The pipes to the heater were aparently cut off and blocked off with bolts, plus the thermostat had three holes drilled in it.
The pipes and the thermostat were replaced and the system drained and bled, when she got it back it was pumping out hot air.

Where it is now...after 10 miles or so the temperature gague goes off the scale and up pops the red flashing light of doom.

After rummaging around underneath, the two pipes to the heater are cold, and one pipe to the radiator is super hot, the other one is luke warm.
The luke warm one goes to the back of the thermostat, the stinking hot one goes to the drivers side on the engine.
The radiator is luke warm and when the electric fan is switched on (manual) it goes cold straight away.

Never having been involved with water cooling trickery before, I'm looking for some help.

I'm thinking two things, that new thermostat is "pooh" or the water pump is lacking any gusto, but I am clutching at straws and hoping one of you will point me in the right direction.

All help appreciated

Thanks

Andy

[937carrera]

More questions first:

Was it overheating before you took it to your usual garage

Does the red light flash when you switch the ignition on from cold

Does the fan come on, at any speed - likely to be a two speed fan

Where is the water level in the rear header tanks

There's quite a lot of good info in the wiki - top of the page

[andygriffiths]

Hi,

It wasn't overheating, although the gauge was on the hot side.

Yes, red light flashes when starting, then goes out.

The fan has been changed to a manual two speed switch on the dash.

One tank is full the other half way between min and max.

[937carrera]

The radiator is luke warm and when the electric fan is switched on (manual) it goes cold straight away.

So the fan you are referring to is the radiator fan, not the fan for the heater / fresh air here.

What goes cold - the fresh air vents of the radiator ?

Sorry to be asking what looks like daft questions, but the radiator cooling fan switches on and off in normal circumstances. If it doesn't come on, then the coolant will overheat, so what is happening is normal if you aren't putting the radiator fan on.

There's a flow diagram somewhere in the WIKI which will be handy, but I can't find it at the moment

I assume all these modifications are previous owner ??

[andygriffiths]

There are no daft questions.

The heater fan works, and pumps air out, but not hot air.

The other fan is a manual switch for engine cooling and radiator goes cold, when testing, not that it gets really that hot like the engine.
(I'm guessing someone has wired in a manual switch as the radiator thermostat wasn't working)

I have the radiator fan on high when driving, but red light still comes on.

When the radiator fan is switched on, the air flow is forward, is that right?

From what I read the heater should be independant from the main thermostat, but pipes are cold/luke warm.

It's almost like the water is not circulating properly.

[937carrera]

I have the radiator fan on high when driving, but red light still comes on.

OK, so you do have a problem. The red light can come on because of overheating or low coolant. from what you have described the needle is high (where) so the light is flashing

When the radiator fan is switched on, the air flow is forward, is that right?

errm, no. When you drive forwards airflow is from the front to rear. The fan increases the airflow, so pulls more air through the rad, also front to rear.

I'm trying to find that flow diagram for you, things will make more sense

[Cobra88]

sounds like a load of air still up the front.

mine is early cooling system Nov 84 DG

mine only got like this after I drained the whole lot down inc radiator and the cylinder liners.
was an absolute swine to get the air out.

never had any trouble before when I just drained water pump area to work on pump/thermostat etc but nightmares once properly empty

can you tell us what year the 1.9 is (early or late cooling system)

Regards
Rick

[937carrera]

Here's a thread with the cooling diagrams.

https://club8090.co.uk/forum/viewtopic.p ... &p=8049486

The control in the cab is simply a diverter valve that allows coolant to flow across another radiator that allows heat to be blown into the passenger compartment. If the engine is hot, that should be stinking hot too. Leave the heater of full hot for the duration of any tests.

It could be loads of air up front, but given the amount of running I would have expected any air to find it's way out by now.

Best way to bleed is to follow Brickwerks advice http://www.brick-yard.co.uk/forum/bleed ... 29710.html

I'm also thinking a blocked radiator - hot water to it, not hot water from it, so either super efficient rad, or no flow.

Diverter valves do jam us as well

[andygriffiths]

It's a G reg, I have no idea if it is old or new cooling

Here's picture of it.

[937carrera]

That's late then

[andygriffiths]

I did red and blue dots on that diagram to explain it better (maybe)

I can't think that both radiators would be blocked, so probably has to be air?

I think I'll go for the whole bleeding bit next weekend.

I think I might need to rewire the cooling fan too.

[937carrera]

Good work,

If I understand correctly, then there is no hot flow to the heater circuit and the return pipe from the radiator is cool.

That could be an airlock, but IMHO it's more likely to be a blocked radiator. If it were me I would take the rad off and flush it through, both ways.

Before you do that though, it would be worth undoing the bleed on the top of the rad to allow any trapped air to escape

And definitely put the cooling fan back to standard, the switches do fail, but on the whole they are the most reliable solution

[AngeloEvs]

It seems the new thermostat has increased the running temp given that the original one had three holes drilled in it and the temp gauge needle was still on the high side. Apart from insufficient coolant or an airlock, retarded engine timing, etc, faults in the temperature gauge circuit can cause erroneous readings.

Whereabouts in Cambridgeshire are you?

[ajsimmo]

Sorry to bear bad news, but that's a frankengine. Someone's bodged an early type engine into a late van. You have two separate thermostat housings fitted! That needs redoing from scratch to put back to standard, or you'll always have problems. There's so much wrong in that pic it makes me shudder!
And a Weber (blurgh!) Fuel filters in engine bay too.

Sent from my ONEPLUS A3003 using Tapatalk

[937carrera]

To be fair it isn't his diagram, it was modified with the blobs from one which itchy put up in the other thread I linked to.

Your experienced eyes picked up things I didn't, I just went on age, and based on what we have learnt so far I am not that surprised. I thought it was quite hard work to get an early engine in a late body, maybe this is the proof.