Thread: Funny Overheating Problem with Carby V8

Funny you should ask, as yes, I did finally figure it out and was about to update the thread.

I did everything on the list, including checking the timing was at 6 BTDC and replacing the ignition module, and using a big syringe to put a bit of vacuum onto the vacuum advance and make sure it moved and stayed put. (They're well known for leaking.)

All was fine but when I pulled out the plugs for the compression test they were all white. I did find that by richening the mixture the cooling problem seemed to be fixed, but the original carbies were in the usual original condition so I replaced them with some new ones I had.

That's when my problems really started, because no matter how rich I made the mixture, the cooling problem was there and the plugs would be white after a run. It's at this point that I started keeping notes so I could see what I'd done and not rely on my dodgy memory!

I tried cooler plugs, going from NGK BP5ES to BP6ES. It also seemed like there was just too much air getting in, so I went right through the breather system and checked everything. Then I went through the brand-new cooling system, and tried taking the guts out of an old thermostat and putting that in.

I kept ignoring the timing as it was set at 6 BTDC, as per the manual, but then I saw a neat quote on a website that, "90% of carburettor problems are electrical", and realised the timing would be worth looking at. 9 degrees was better and then 12 BTDC transformed the old car, making it take off quicker but also suddenly the cooling was normal. It would heat up slightly under load or while idling, as normal, and once on the highway it would cool down again, the way it was supposed to.

So the lesson here is to be methodical, keep notes, and check the simple and basic things first. Once I'd replaced the cooling system and the compression test was good, it had to be something else. As any old hand here will know, if I'd done that in the first place I would have saved myself a heap of trouble.

. . . and the problem came back, just before we were going to take the Rangie to Broome for Christmas. (To compound the tragedy, we ended up taking our clunky '91 Magna instead, making it in by 9pm on Christmas Eve, and then over the next three weeks the headlights, CD player, and muffler packed it in.)

So, now I'm convinced it's that one part I should have changed but didn't because (SIGH) it was too much trouble at the time - yes, the camshaft. Overheating in specific situations, power slightly down again, it's got to be a timing chain or cam or both, and I know they're a bit old, so no excuses now.

I'd almost rebuild the whole engine . . . quicker in the long run.

My V8 110 does the same: normal when tootling around, but as soon as I hit a hill or the highway, there goes the temp gauge.

I've swopped the 110 visco and fan for a used RRC visco and fan: it got worse.

So now I'm also going down your route:

- radiator check & clean
- flush the system
- new visco
- check timing

If I get to the end of that list, then stuff it, I'm putting a Lexus V8 into the old girl!

That's when my problems really started, because no matter how rich I made the mixture, the cooling problem was there and the plugs would be white after a run.

did you top up the oil in the new carby's?

Originally Posted by jakeslouw

- radiator check & clean
- flush the system
- new visco
- check timing

If I get to the end of that list, then stuff it, I'm putting a Lexus V8 into the old girl!

Well, I'm going to rebuild another Rover V8 eventually and put that in. That's easier in the long run than mucking about forever chasing problems. But be sure to do a proper compression test on yours as the head gaskets can also apparently cause this problem. I haven't pulled the heads as my compression test was good, I haven't lost any coolant, and the cooling system hasn't been pressurised. However, in about three months I'll no doubt update this thread to say that it was indeed the head gaskets!

And yes, I did make sure the dashpot oil was all good. That's been the infuriating thing about all of this - I've done a meticulous job of what I did replace but I should have just got stuck into it properly. (Actually, I should have measured the cam lift while I had the rocker covers off, too.)

Davo, one more thing
The condenser in front of the radiator, is it clean, the fins can block if it's never been cleaned,
resticts the air to the radiator,
i clean mine at the local car wash, the pressure hose isn't to powerful at ours anyway

And for goodness sake, put a proper thermostat back in before you melt the back off the motor

Oh, pshaw, the Watchdog sender is on the back of one head and hasn't registered anything awful . . . but, yeah, a proper thermostat is going back in when the manifold is off. Because you're right, it might cause trouble the way it is.

I did clean out the aircon condensor really well, too. That's the thing with this - I've done just about everything that you can think of to fix it. It's only been about 14 months of work so far. "Only"!