Running a bit hotter at speed

[saxon]

Just wanted to pick brains on here as I have an unusual issue! Car is a 1992 precat which has never had any overheating issues before. Temp was always rock steady in the middle of the gauge when at speed and then when in traffic fans would cut in and out as normal.

About 4 years ago Griff was recommissioned after an extended layup, coolant flushed, outriggers replaced, one SPAL fan was replaced, lots of work on electrics, brake lines, fuel lines, steering rack replaced etc. Upon driving home I noticed car running hot on motorway and heading for red zone with fans on constantly at motorway speed.

Returned car to APM automotive who then re-flushed coolant and fitted re-cored radiator. Car still running hot at speed.

Fitted a TVR front diffuser (which my car never had/needed before) and although this helped a little car still running at or above white line on motorway with fans constantly on.

More recently my new engineer has checked the coolant system for leaks and airlocks, none of the hoses are pressurised, no sign of steam from exhaust, temperature and fans in normal driving and when stationary absolutely normal and car does not overheat in traffic etc. This problem only occurs above about 2500rpm on the motorway. After a 200 mile drive no indications of coolant loss at all.

Car is now with a renowned TVR expert who suspects possibly inaccurate temperature sender or thermostat inserted wrong way around. Hoping it is something simple like that but obviously worried in case it is more complex. Just also wondering if any of you suffered similar symptoms and what it was.

Interested in any views.

Saxon

Edited by saxon on Tuesday 16th June 14:48

[saxon]

No it's original as far as I know (owned car for 23 of the past 28 years). I was wondering about water pump not working properly at speed. Not knowing how it is constructed I would be very interested in whether the water pump TVR use can suffer from this as I came across some threads on a BMW forum I think it was detailing this very issue.

Does the impellor sit on a spline in TVR waterpumps?

Is this feasible - if so it will be a relief!

Saxon

[saxon]

Hi there, yes only judging it based on the temperature gauge - that's one of the areas my TVR expert is going to investigate by putting another sensor on the engine and comparing I think.

As you say replacing the thermostat probably makes sense too. It had a new radiator cap 4 years ago as a precaution too.

Saxon

[saxon]

Yes hoping it's not a head gasket issue or anything similar! Not using coolant though and not pressurising hoses so staying optimistic! It's in good hands at Lawfield Engineering in the old TVR factory and under the care of Brian Hosfield who was Peter Wheeler's personal race mechanic!

So far he has found low antifreeze concentration which is odd as it hasn't been topped up by me or driven much since APM Automotice changed the radiator and flushed the system 3.5 years ago. He also found the otter switch was the wrong one and triggered at 96 degrees not 88, again odd because the car has only been serviced at TVR specialists like Fernhurst and APM Automotive.

Good suggestion re: the new fan possibly being wired to push not pull, I will have that checked, although that still doesn't explain the fans staying on at speed as most of the cooling effect at motorway speeds should be from forward airflow throught the radiator I would have thought.

My gut feel is that it could either be a dodgy thermostat, a slipping impellor on the water pump which copes at low speed but not high speeds or possibly a defective radiator in which case I might think about an aluminium one. The radiator seems less likely though simply because the hot running issue has now happened on two radiators.

Saxon

[saxon]

I think the plan going forward is to rig up a second and known accurate sensor to check if the car actually is running hot. If it is then it points to inadequate cooling capacity at speed and I am sorely tempted to replace the water pump as the radiator was recored a while back and this problem has now happened on two radiators.

If all else fails I guess an aluminium radiator would provide more efficient cooling, but obviously shouldn't be necessary if the engine channels are clear, the coolant levels are correct and the thermostat is working correctly.

Saxon

[saxon]

That's very good to hear Chris - I will send that idea to Lawfield Engineering in Blackpool as they are the ones who will be investigating this when D&C Trim have finished working their magic!

For the benefit of future owners I will post here when I find out what is going on! I think Brian at Lawfield plans to check the temperature sensors anyway before swapping anything over like water pumps etc. The dilemma though is that spending £75 an hour to diagnose the problem might be more expensive than biting the bullet and replacing the water pump (£100) so it's about striking a balance between spending time and money investigating v just bolting on new bits!

In the meantime here's some pics of what D&C have been up to!


Saxon

[saxon]

I'm happy to report I have just collected my car from an absolutely superb retrim at D&C Trim in Blackpool, the guys there went the extra mile to make everything utterly perfect and were just a joy to deal with!! Brian Hosfield at Lawfield Engineering was also absolutely superb and has made all sorts of enhancements to the car and has sorted a whole host of issues and niggles including:

Fixed electric wing mirrors
Dramatically improved cabin heating and ventilation by relocating a powerful SPAL fan into a custom heater box placed in the front bulkead (mien being a precat had it originally in the front wheel arch)
Custom built LED panel for backlit heater control perspex panel
Sorted out a flatspot on accelerating
Tuned the timing to perfection to eliminate pinking
Fixed duff speedometer and mileometer transducer
Repaired heater control system

Finally and most importantly cured my hot running at speed by fitting a beautiful aluminium TVR racing radiator with cowls. In 288 miles down from Blackpool yesterday the temp gauge barely got to the middle of the gauge and the fans were only on once as I crawled out of a petrol station.

I haven't managed to take any proper pics of the retrim but I will. In the meantime here's some pics of her in her spiritual home I took the other night!

I couldn't be more thrilled!

Saxon

[saxon]

[saxon]

Lucy,

It did indeed, but that was a bit of a surprise because apparently a recored one was fitted by APM Automotive 3 years ago and the car has only done about 500 miles since!

Saxon

[saxon]

Cureton - thanks, you're very kind. The car has the OZ Racing multispoke alloys that were an optional extra from the factory when new. The tyres are Toyo Proxes T1-S.

Kind regards,

Saxon