Overheating (with a twist)

[cavebloke]

Hi All,

I have what seems to be the usual overheating problem when I run the car on a hot day or I get caught in traffic the needle edges into the red. On a cool day it will run fine for hours. This is a new problem and I've had the car running fine for years.

I assumed faulty thermostat so I've just finished dismantling the housing to find a previous owner has completely removed it. There's just an empty hole where the thermostat should be.

Both fans come on at 90 and are working fine. I've checked the oil and there's no sign of cross-contamination. Also no oil in the drained coolant.

Car is an unmodified 430 pre-cat with an alloy radiator. It had a full rebuild 3 years ago. The water pump is clearly working as I can see water flowing into the swirl pot.

Any thoughts would be very gratefully received. My top idea is a radiator blockage but is there any way to clear this without removing the radiator?

I have a new thermostat, would you refit it given this is a summer only car? The car heats up pretty quickly without it any way.

Cheers,

Simon

[cavebloke]

Thanks for all your replies. I think I will put a thermostat in as I don't like the idea of not having one. Steve Heath talks about drilling a few holes in it to prevent "thermal shock" and allow a small amount of water out to the rad even when cold. Has anyone done this on their car?

I've bought one of those laser thermometers to see if I can work out if there's an air lock forming somewhere or a blockage in the radiator. Plus it looks like a fun gadget.

On the fans, one of them failed last year (seized solid) and I thought originally that was the source of the problem but there's a brand new one in now and I still have the same problem. What's the best method to test if the fans are running at maximum efficiency? I rebuilt the car 3 years ago and cleaned up all the earths then; but the wiring is old now and has been in a very hot environment so may not be work at its best.

I'll post back when I have it all reassembled and see.

Cheers,

Simon

[cavebloke]

ChimpOnGas said:

If I was the OP I'd do the following:

1. Remove the rad and back flush it

2. Clean the rad fins of insects and road debris

3. Check and clean the fan earth points and it's connectors, all of which corrode badly on these cars causing significant current drops and slow running fans

4. Replace the thermostat if missing or test if in place, these engines were designed to run an 88 degree thermostat, the use of a cooler thermostat will not help an underlying issue with your cooling system so fitting one is pointless, if the car overheats with the correct 88 degree thermostat something is wrong with your cooling system, the solution is not to fit a lower value thermostat!

5. Optional: Replace both fans with new units from Spal, the latest offering from Spal that shifts a bit more air and is longer lasting than the original used by TVR is VA10-AP70/LL-61A and costs £132.00 each including VAT & delivery if you buy direct from Spal (Call Maggie on 01905 613714 Ext. 206)

Thanks for taking the time to give me a plan of action - it all sounds like sage advice to me. I've just got to make the time to get on with it now.

Do you think I need to remove the rad to back flush it? Would there be any issues with doing it in place if I control the exit water flow using some old piping?

Cheers,

Simon

[cavebloke]

Penelope Stopit said:

I thought I better post this information again as I am worried that you have missed it

Thanks for this. I've added this to my list and particularly after reading carsy's old thread. I have a multimeter already so I will set to work on trying to figure out the problem. This may be the most likely thing now as the rad is a new-ish alloy one, so it's not that likely to be blocked with crud (I will check and back-flush though).

Simon