Flushing the cooling system

[Robbie693]

In an effort to fix my too hot running problem I'm thinking of using a rad-flush additive. Has anyone had any problems from using this stuff?

[Tonyw]

Robbie,

These only tend to work if the coolant tends to be "muddy" you will probably find that hard flakes of rust from the block have partially blocked the tubes in the radiator, this assumes of course that your thermostat, fan etc are in good working order and your radiator fins are not fragmented or blocked with bugs, worth a try anyway to clean out the system as if you end up with a new or cleaned out rad then you will at least have a nice clean system, do not forget to open the heater valve.

Tony W

[hatman]

Robbie, your best bet would be to take the radiator out of the car (a straightforward job) and backflush it by sticking a garden hose into the outlet pipe at the bottom (turn the radiator upside down, of course) and let it run for a while till all the gunge and detritus has gone.

Whilst the radiator is still out you can then give the block and heater system the same treatment to wash out all the years of accumulated muck, leaving everything as clean as a new pin inside when you re-assemble and re-fill with de-ionised (important, that) water and, preferably, 5-year antifreeze.

If it overheats after that you've probably got a duff water pump or the airflow through the radiator is blocked somehow.

[1964 S1]

And while the radiator is out, lay it flat, front face down and flush the fins on the outside with the garden hose as well. You can gently straighten bent fins with a tiny flathead screwdriver to aid air flow. Be careful not to crack any water tubes. Good Luck.

[iain.hamlton]

Robbie,

Are you sure the car is getting hot? Are you confident the gauge and sender are accurate? Is the voltage stabilizer producing 10V rather than 12?

best regards, iain

[Robbie693]

Thanks for the replys,

I have backflushed with the hose before, although I didn't remove the rad, just ran the hose through the bottom outlet on the rad and the engine.

Good point Iain, I have wondered this but I fitted a new Voltage stabiliser, sender unit and thermostat. The gauge reads about 90 deg when the fan cuts in which I assume is the correct temp for the fan so the gauge must be telling the truth?

Even though the fan is running, the temp goes up to just below the red sector before it starts to cool again. It has never boiled over but it is a bit scary.

[iain.hamlton]

It sounds as if your gauge is telling the truth.

Does the car get hot on the move? Or does the fan only cut in when you are in traffic? What sort of fan do you have? I wonder if it's man enough for the job.

My car does something similar, but never needs the fan when the car is moving. When idling in traffic, the fan brings things back to normal (albeit not before the needle rises a bit first). I have an inexpensive fan held on to the radiator core with tie-wraps. I also have an override switch so I can turn the fan on in traffic rather than waiting for the otterswitch.

best regards, iain

[Robbie693]

Hi Iain,

On the move it usually hovers just under 90 deg on a warm day but if I come to a traffic jam and have to stop suddenly it rises in temp rapidly. The fan cools it gradually down to about 95 deg but not before it's gone up to 110-115 deg or so.

I'm going to get a thermometer and put it in the filler neck to get an accurate reading to compare with the gauge, but figured a flush out wouldn't do any harm at the same time

[hatman]

Try running it without a thermostat - see what happens then.

[Tonyw]

Robbie,

Running without a thermostat might work but the water might just circulate to fast to spend enough time in the radiator to cool, the thermostat also slows the flow as well as providing a system to heat up the block fairly quickly to operating temp. Best to rip the guts out of an old thermostat and just run it with the restriction ring intact. You should see a surge of water through the radiator as you rev the engine up and down with the cap of, this will indicate a reasonably functioning water pump.

If you are comfortable that the tempretures you are quoting are true then you do appear to have a cooling problem, try to see if the tubes that are visible through the radiator cap (removed) are blocked, i.e. if you can see ten tubes and three have detritus in them you can almost bet you radiator is 30% blocked. To fix this of course the top tank has to be removed and the tubes cleaned out, this is more common than people think.

Fixed fans only work really when the car is going very slow or stationary, once a car is doing 20kph or more it is air flow from the front of the car that cools the thing, i suppose you do have good air flow through the radiator.

TonyW

[Robbie693]

Thanks Tony,

The top tank did look pretty clean when I last flushed it but I didn't really peer down the tubes (it's a 3 row core). I'll check this out.

There's not really anything to block the airflow so I think this is OK.

The water surging when reving the engine; would this be noticable with the thermostat in place?

[richardcox_lotus]

Hi Robbie

My Sprint has pretty much the same symptoms - I have a 3-row rad, original fan set-up with Otter switch etc. It gets hot, but the fan on mine doesn't really kick-in until about 98, so by the time its whirring the gauge is showing 104-105. Never boiled over though........

I'm uncomfortable with removing the thermostat completely - it is there to do a job - so it's my intention to flush the system soon, I'd be interested to hear how you get on. Also, my other thought was to replace the fan set-up with a Pacet or similar - more efficient, & the opportunity to get the fan to start at an earlier setting.

[elanmac]

Hi Robbie
What temperature thermostat do you have fitted. I had a 88 degree fitted and my guage was showing 95. I fitted a 82 degree thermostat now my tempguage shows 85 my fan cuts in at 90 and drops the temp to 85 when in traffic.
elanmac

[Robbie693]

Good question Mac,

Dunno actually I asked for a 'stat at Matty's and they just gave me one, I forgot about there being two types..

[264889socal]

I ran into an interesting situation last week. Took the Elan on its first real tour of about 1200 miles throughout Central California. Under all sorts of driving conditions, the water temperature never reached what I would consider an approptiate operating temperature. In fact, couldn't get it over 165F. While in the mountains, and snowing and forgot how cold an open car can get, the engine was operating at only about 110 to 115F. So cold the heater was of little use and I shut it off as it actually cooled the footwell.

Figured the PO most likely did not install a thermostat when rebuilding the engine. Decided to live with it until I got home and check it our before I went on another tour on Sunday morning. Saturday night, I purchased a new 180F thermostat, with the intention of installing it that evening. Pulled the thermostat housing and low and behold, there was a near new 180F thermostat. Hmmmmm. Looked perfect and was not locked open in the failsafe postion. Hmmmmmm. Changed it anyway and the next morning took off for the meet. Drove about 20 miles through cool and misty conditions and the temperature never rose above the 160 mark. Got to the lot for the meet and parked the car. When waiting in traffic for the group to leave, the temperature actually rose to about 185F. Reved the engine and the temperature dropped immediately to 160F. On the tour, I got to thinking and realized the thermostat cover'outlet, while the right shape and orientation, was the wrong unit. The opening in the housing is larger than the thermostat's outer diameter. When the temperature rises and/or the engine rpm is raised, the thermostat it pushed out of its location and the water passes around the outside diameter of the thermostat.

Will pull the housing off today and weld several spots around the inside of the housing and mill flat to prevent the thermostat from being moved.

Hopefully this will get the car up to temperature, increase performance, and mileage.

Rob