overheating GTV

poohbah · January 15, 2022, 12:56:27 PM

The fuel filter seems clear, and I've had no trouble with starting since.

I also don't want to jinx things as I haven't been able to do a decent run in traffic, but apart from the immediate short test drive after changing the thermo (when it still ran hotter than I'd like) it does now seem to be holding around 80C - at least beyond the point at which it was previously heading north to 90C.

I won't be convinced til I've taken it out for a proper test - hopefully will get time today. At this point I'm going to assume any optimism is misplaced and that the investigation will have to continue.

Craig_m67 · January 15, 2022, 05:46:47 PM

Quote from: poohbah on January 15, 2022, 12:56:27 PM
The fuel filter seems clear, and I've had no trouble with starting since.

How old is the hose (it collapses on itself, before leaking...)
Is there another filter at the tank, or inline
What about the little basket filter things in the carbs just before the needle valve...

But yeah, I don't think the fuel system is in anyway related to your overheating problem.. just another "while your in there, scope creep" hole to go down.

Has anybody pressure tested the cooling system?

poohbah · January 15, 2022, 07:51:45 PM

No, haven't pressure tested the system. Just got back from a longer drive, and while it is definitely better than before, after being stuck behind a slow coach 4WD for a fair while, it did end up hovering around 85-90C mark for the rest of the drive home. So still needs further investigation.

poohbah · January 17, 2022, 02:17:06 PM

I'm sure this is just peripheral to the issue, but yesterday I discovered the clamp on the main bottom hose from the rad where it joins the water pump and 3-4 of the little retaining nuts on the top edge of the pump assembly were not tight-tight and there was some dried residue from old coolant seepage around them. So they are now all tightened up.

Also - what's the giveaway that a hose should be replaced - squishy or firm? The bottom hose is definitely pretty squishy.

Colin Edwards · January 17, 2022, 04:00:19 PM

More often than not the lower hose "should" be firmer than the top hose. The lower hose is usually not subject to as much engine rock, vibration or movement as the upper hose. The upper hose should be more flexible than the lower hose so as to not stress the radiator inlet and engine outlet fittings.
If your going to replace one or two (recommended) hoses, would be a good time to have the radiator professionally cleaned. Looks like it needs a bit of love!

poohbah · January 17, 2022, 06:01:03 PM

Thanks, when I get around to pulling out the rad I'll probably replace at least the main ones.

NSharpley · September 25, 2022, 09:49:56 PM

Any updates on this?

Did you get to the bottom of it?

Interesting read.

I have a track car with an overheating issue, keen to know what yours turned out to be.

poohbah · September 26, 2022, 05:10:19 PM

Haven't gotten round to pulling the rad or changing hoses yet, as I have hardly had the car out for the last few months. Just got her up and going again after winter slumber and no overheating issues in the 40 or so minutes I had it out on the road. But I will get around to it now weather is improving - need to source the hoses first.

Last two days had a more immediate issue - getting it started. I had to suck fuel up to the carbs and the old plugs were completely cactus. But have fitted new ones and all good for now. Except will need the carbs balanced and tuned. Big carbon buildup on plugs from cyclinders 1 and 3, and the other two were black and sooty, so seems it is running rich in general as well as having uneven mix between individual cylinders.

poohbah · January 12, 2023, 09:58:41 PM

Wow - September since I last mentioned any progress.

Good news is I finally got around to removing the radiator today and am pretty certain I now know why it was running hot after about 30 mins.

While the core looked fine on the inner facing side, it was crumbling in two separate areas on the front facing side where it was hidden by the AC condenser. To be honest, I'm amazed it managed to function at all.

Dropped it into a local radiator shop and they are making me a new one with bigger more efficient core made of newer materials, and I should have it in about a week's time.

Also took the opportunity to remove the condenser (also in poor condition) - I had previously removed the compressor and rest of the AC anyway - which should significantly improve airflow to the new rad. I'm probably going to replace the two main rad hoses while access is easy - they're in okay nick but I may as well.

And I've been able to scale off the surface rust on the body/support under the radiator - it was a little bit crusty under where the core was crumbling.

So hopefully, I'll have a properly functioning cooling system in the next week or so.

But wondering whether I should look at fitting dual fans - the old rad only had the one, which might be sufficient when I fit the new one.

poohbah · February 12, 2023, 10:30:07 PM

Fabrication of the new radiator took a bit longer than initially expected, but I picked it up on Friday and fitted it yesterday.

System fully flushed, filled with fresh coolant, fan refitted and running as normal. I took the hoses into the workshop a couple of weeks ago to ask about matching replacements, but the guys looked at 'em and reckoned they were basically as new, so no need.

Took it for a decent run today and worked beautifully, sat around 80 the whole time, and fan kicks in as it should if it gets over it. With the old AC condenser removed, the rad now has much better airflow.

Now I just need to get onto removing the inlet manifold and carbies to replace the mounts and flange gaskets - definitely got a vacuum leak on the front carby.

But the nuts are super tight - I'm a bit wary of snapping studs, so will need to think my way through. For now, I'm just happy I can take her out without fear of cooking the engine.