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

[O mage]

Has the water pump been changed ive known impellers come loose on the shaft and it sort of tries to pump when cold then slips on the shaft when hot.

[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

[O mage]

saxon said:

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

No they are usually just pressed on to a plain shaft. It would be worth taking it off but once you have you might aswell replace it anyway. I doubt the therm is in the wrong way but that is worth taking out and checking it is opening fully. I would take both off and check the water pump with some big grips if its not at first apparent at least you can rule out both problems. Id say its likely one of the two that's at issue.

Edited by O mage on Tuesday 16th June 15:30

[blaze_away]

Are you gauging the engine to be running hotter based on the dash board didplay ?

If yes would suggest you tepeat the excercise and see what Rover Gauge data looks like in comparison.

You could have clag build up around the sender unit or it could need replacing.

FWIW There is a thread about fitting a new dash sensor in the old Rover sender location. Highly recommended

[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

[O mage]

saxon said:

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

It doesn't sound like a gauge problem if the fans are on all the time the gauge is probably right.!

[magpies]

O mage said:

It doesn't sound like a gauge problem if the fans are on all the time the gauge is probably right.!

agreed

generally once above 30/40 mph the fans should (almost) never come on. Could do with checking the otter switch.

[Hedgehopper]

It could be something really simple like an airlock. I have had that happen after changing the coolant and bleeding the system. It has always benefitted from being bled again after several hot runs days later. The problem on my car has always been air in the top heater hose at the back of the engine.

[neutral 3]

Renowned TVR expert......all I can say, is chose Very carefully who you let lose on the car.....

[David Beer]

Hope it’s not a head gasket , mine was!

[Mr.Grooler]

The new cooling fan wasn’t somehow connected to run backwards was it? (I wonder if it could still flow air the wrong way at low speeds - less efficient obviously - but at it higher speeds it would effectively be trying to stop the airflow?)

But yes, check the temp senders first for gauge and fans!

[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

[spitfire4v8]

saxon said:

So far he has found low antifreeze concentration. He also found the otter switch was the wrong one and triggered at 96 degrees not 88

Neither of which are contributory factors. Antifreeze reduces the heat transfer of water so less a/freeze actually should be helping reduce temps not increase them (localised boiling issues aside, but you don't mention boiling over just high temps) , and a high otter switch should definitely not be switching in .. it would be even worse with the correct switch fitted as the fans would be on even more of the time.

There is something much more fundamental going on.

[FFMan]

Suggest you get the radiator recored. Flushing is a misnomer, not half as effective as people think.

[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

[Simon.b]

I recently had an overheating problem which came to a head when one fan stopped working completely. The problem was the spade connectors on the shroud. The wires for on fan had become corroded and I guess introduced a resistance. The connector also looked as though it had been getting a bit hot. Cut the spades off soldered new ones on with a new block from ebay and that fixed it, all back to normal.

Good luck, hope you find it.

[ChrisW500]

Had a similar problem on my 400 it turned out to be the fan sensor in the radiator. Changed it and a good coolant burping session and normal service was resumed!

[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