1980 Land Rover Lightweight V8

[generallee]

Yeah, but apart from that, it's good?
I have been following your overheating thread but can't offer anything constructive.

I'd love a V8 series Landy, but after reading this.... I'd still love one.

[dodgerover]

Just a thought have you checked that there is no muck jammed into the bottom of the holes for the head bolts, it's surprising who little will lead to them bottoming out and giving an incorrect torque setting especially if the heads etc have been skimmed.

It's probably not advisable but in the past after cleaning them as much as possible I've put an extra washer under the head bolts to allow them to torque up without bottoming out.

[giuliettaevo]

My dad once had an old Mercedes w108 which started overheating. He changed everything but it kept doing it. In the end they discovered a hairline fracture in a cylinderwall.

Seeing you already changed engine it's not very likely that this is your problem.😅

[kevins]

as long as it doesen't foul anything a thick washer washer under the head bolt on an alloy engine is a good idea, probably not an issue on a RV8 but when I used to work on YB cosworth engines the head would deform under the head of the bolt and lose gasket clamp, obviously still need to be sure you have the correct thread engagement.

[ducklooker]

Through everything you have been afflicted with I see no mention of assessing coolant flow through the radiator??
I had issues with an escort (the mechanical version) and it ended up being either rad weld or egg whites that loved to move about en masse but not show themselves when I back flushed the bloody thing seventy million times or so.......
By the way, what made a Lightweight a Lightweight because the wee bit of alloy they've trimmed off wouldn't do much?

[dieselmax]

That's a smart lightweight you have there. Are all the radiators you have tried the standard 4-cylinder rads? I would try running a V8 rad, that belongs to the engine, ideally with the viscous fan as well.
Lightweight refers to it being able to be stripped down quickly to make it light enough to be air-dropped I believe. The doors do lift off, and several other body parts can be removed in minutes, without tools.
In complete state, they are not any lighter compared to a civilian landy I don't think.

[fredje8v]

How about the waterpump, is it still the old one. Bad pump would cause it to cook in the engine while the radiator and heater are still ice cold.
Broken thermostat (or incorrectly fitted) would cause the same issues

[thomfr]

If the temp switch jumped up I wonder if you had an airlock somewhere in the system!?

Thom

[welshpug]

had this problem with an early Pre defender 110, baffled us for months, only happens because you get voltage feeding back through the lamp to the other wise of the relay for some reason due to the particularly low current draw of LED's.

you need to wire up individual telltales for left and right, or not have one.

[gtviva]

You need a particular type of flasher unit when you only have 1 telltale on the dash, you cant use a standard flasher unit, they are widely available as most older vehicles had them

[kevins]

I think you could use what you have with a couple of diodes, the anodes connected to each indicator circuit and the cathodes both joined and feeding the warning light. (assuming negative earth).

[jimi]

To overheat a wire like that you must have created a dead short from live to earth (+ve to -ve or vice versa) through the wire, your lucky it didn't go up in flames.
When your testing stuff like that stick a temporary fuse (2A/5A) inline, that way a mistake in wiring (like a short) will blow the fuse and protect the wiring etc.
You can get inline fuse holders (car type) with a few inches of wire either side for peanuts on Amazon/eBay, I use one with croc clips on either end for fault finding circuits that are causing problems, I adjust the fuse size to suit the circuit.

[kevins]

yes that would work.

I would also add a warning light between the dotted line and earth, it will also come on with the thermo switch which I like, if you don't the dotted wire will need a diode.

[jimi]

That will work, the bypass can come off the same feed.
Run a new fused 12v supply direct from the battery to supply the fan via the relay, that way there's no real increase in load on your existing wiring. 👍

[jimi]

Jan 20, 2024 13:11:06 GMT kevins said:

yes that would work.

I would also add a warning light between the dotted line and earth, it will also come on with the thermo switch which I like, if you don't the dotted wire will need a diode.

Good idea, could also use a switch with a built in warning light 👍 (will need a diode as well)

[kevins]

If you are not worried about the warning light, you just need to connect one side of the switch to a fused 12v and the other to the line which triggers the fan relay, the diagram above will work fine.

If your switch has a integral LED it will have a 3rd terminal which is usually earthed, if you don't want the light don't connect the earth terminal.

if you want the LED to only come on with the overide switch, connect the switch earth and put a diode with the triangle pointing away from the switch in the wire between the switch and terminal which triggers the fan relay.

[jimi]

Correct 👍 the diode blocks the reverse feed so light will only be on when the switch is on.

[logicaluk]

Did I see your thermo switch was in the top hose? If so IMHO it should be in the bottom hose, as the fans are there to cool the radiator when it's not cooling enough.
Dan

[kevins]

Even the OEM's can't agree on that one, one school of thought is as you say, the other is the top hose is the hottest part of the cooling system and this is what you want to control and react to as quickly as possible, given the history of this I'd stick with the top hose!

make sure the sensor is in the bottom of the top hose though, if it's in the top there is a good chance it will be in air.

[giuliettaevo]

On modern cars the signal for the fans to come on is send by the ecu. Which uses the engine temp sensor to determine when to switch on and off. That sensor is usually in the cylinder head or near the thermostat.