Now sorted - the age old problem of coolant replacement

[Blokko]

Read all of the various posts on the archive regards coolant replacement, but I'm still struggling...

 

1.6 Rover K Series – ex academy. Had to change the hose from the top rail down to the thermostat (no heater) due to a leak. I had already filled the system once – this is attempt II

 

Whereas prior to the change the water temp was rock solid on 80 Celsius, the system is now running 10-20 degrees higher than before. I'm assuming that the issue is not going to be the thermostat, the temp gauge or the fan - and that what I have here is an airlock somewhere (as everything was fine and dandy up until I changed the hose).

 

I drained the system by dropping the drain plug off the bottom of the rad (as well as the bolt on the top of the rad) and then took off the (new) hose that feeds into the thermostat. Placed the hose back in position and put the rad drain plug back in place (leaving the bolt on the top of the rad removed).

 

The filling method I went for was to take the hose off the top of the radiator, bend upwards and then gently trickle in fluid along the inside edge of the hose (rather than down the middle) until full. I then replaced the hose onto to the top of the rad and then jacked the car as high as I could get it.

 

Next I filled from the expansion bottle – again at a painstakingly slow rate. Once the expansion bottle was full I tried to manipulate the hoses past the thermostat, but this is difficult with old Caterham rubber items (would be much easier with silicone hoses I guess). I used the end of a rubber mallet to manipulate the pipes as best as possible with the car in the jacked position. I left the car for a while to see if any air would naturally bubble up. After about 15 mis I dropped the car back level and topped the rad up from the screw hole at the top.

 

Fitted a new expansion bottle top, checked everything over and then started the car up. The temperature did not rocket up, but rose steadily – but beyond the point where the fan would normally kick in. Just south of 100 the thermostat opened and warmed up the bottom of the rad and the associated hoses nicely.

 

The temp is now running about the 90 mark and with the thermostat open the fan does kick in. Took the car for a drive and temperature is about the same (90 ish), but the moment I stopped to open the garage door when I got back home it crept back up near the 100 mark.

 

So, what have I done wrong and what can I do to rectify the situation? I've assumed that any air will be between the bottom of the rad and the thermostat – but I've manipulated the hoses as much as I can without risking damage to something. Could there be an airlock between the top of the radiator and the head and, if so, how would I go about sorting that one out?

 

Realise that there are plenty of posts around on this matter, but struggling to find exactly the same circumstances (i.e. no heater and with a thermostat / fan that is clearly working, albeit not at the same temperatures as before). Any pointers / advice most gratefully received.....

 

Edited by - Blokko on 25 Nov 2012 18:26:17

[Stationary M25 Traveller]

See if the air finds its way to the expansion tank and the level drops as it cools down. Remove the cap when cool. Usually air in the heater - but you don't have one.

[Bricol]

Fan working isn't the same as the thermostate working - it indicated the thermo-switch controlling the fan is working.

 

Although I have a heater, my way is to remove bleed screw from top of radiator, and fill through the expansion bottle until coolant comes out the bleed screw hole. Top bottle right to top of thread, and while coolant is running out the bleed screw hole, replace the screw.

 

Start car, and as required, top up the expansion bottle as the level falls. Occasionally, with care as it heats up, loosen rad bleed to check still no air, with bottle full to brim.

 

Replace cap, run until fan kicks in, which normally takes an age as the temp rises so slowwwwwwwly. Leave to cool, top up or drain slightly as required to get to max level line, replace cap. Drive.

 

Done.

 

Car left horizontal.

 

Only mod is a bleed tee in heater pipe, but that is simply bleeding the heater hoses - if yours are blocked, then no bleeding to be done.

 

Worked everytime over the last decade or so.

 

Bri

[John Vine]

It sounds as though you've followed Peter Carmichael's well-established method from way back:

It should be clear that the radiator and expansion tank are both on the radiator side of the closed thermostat. The result is that filling from these points leaves the potential for the cylinder head and block to have plentiful quantities of air trapped. It is a much more successful approach to attempt to fill the block and head with the car level. You do this by detaching the top radiator hose from the radiator and loosening it at the water rail - you can then angle it up into a vertical position and fill with coolant. Filling like this gives you the likelihood only of a small amount of trapped air at the heater.

 

Next, jack up the front and reattach the hose. Fill from the expansion tank with the radiator bleed valve open. When the expansion tank is good and full grasp the lower rad hose and flex it *A LOT*. Angle it until it is horizontal to get air to escape up to the expansion tank. There will be big glugs of coolant replacing air pockets. Keep topping up the expansion tank and when you think you have got all the air out, flex the hose some more. Don't neglect to flex the lower horizontal bit where it attaches to the radiator.

 

Having done this, the only air in the system is still by the heater. If you have the expansion tank high enough, loosen a heater hose and vent the air there. Do everything up and it is job done.

 

The system definitely takes ~5 litres (~10 pints).

The only difference I can detect is that you jacked up the nose of the car after reattaching the top hose, rather than before.

 

JV

[Titanium7]

Had the same problem when I changed to silicone hoses. Previously never had a problem following numerous upgrades etc.

 

Tried all the different methods described on blatchat to fill without air blocks, even vacuum filling with a Pela pump. Finally gave up and installed a PRRT and the system filled first time with no air blocks and holds a steady temperature (80C), no prblems since.

 

 

 

Edited by - Titanium7 on 4 Nov 2012 17:50:02

[Blokko]

Correct John - used the Carmichael method and, as you rightly spotted, I put the hose on before jacking the car (as I was working alone this was the only option). Not sure how much difference this would make

 

Did think about going down the PRRT route (maybe with full set of silicone hoses) but looking to minimise cash outlay at this time.

 

About to revisit the car now it is stone cold to see if the levels drop when I take off the expansion bottle top....

 

Bri - may try that method if I'm still having problems.

 

Cheers for the input guys

 

 

 

[Mort]

I have a similar problem after fitting silicone hoses. Can anyone say if it's normal for the bottom hose from the thermostat to the radiator to be pretty much cold when the heater is on, and only tepid when the heater is off?

 

The temperature gauge seem to be at around 80 when the heater is off, and a little higher when the heater is on. The radiator fan seems to operate OK - although it went through a phase when it didn't want to operate when the heater was on, but this seems to have rectified itself. The coolant level is static at around the 1/2 way mark when cold, and a little higher when hot.

[Bio]

When up to temperature and the thermostat open, the bottom hose should be hot...nearly as hot as the top hose when checked at idle.

To remove air locks run the car with the expansion cap off and the top bleed screw on the rad loose or removed so you can check the rad is full, with the front of the car raised very high.

 

John

[Blokko]

To remove air locks run the car with the expansion cap off and the top bleed screw on the rad loose or removed so you can check the rad is full, with the front of the car raised very high.

This is the one of the things that I was not sure of having read a number of earlier posts. I thought that the system needed to be under pressure to work correctly. Will running at temperature with the rad cap / bleed screw removed cause problems

[Mort]

Thanks John. if I can't get this sorted out I'll have a chat with you at the next Penn meet.

[Nick Chan]

Hi Steve,

 

Sorry to read about your problems. I follow a very similar procedure to you except I run the car up to temperature with the nose high in the air and then loosen the bleed screw on the radiator several turns so the screw rattles in its threads which allows the air to bleed through. I repeat this several times whilst the car is running until the air is expelled and coolant is starting to come through.

 

It can take 10-15 mins with the fan kicking in and out to do this part. A handy tip is to use a towel or blanket over the radiator to help build the temp up esp. on a cold day like today.

 

Nick

 

BTW by this stage, I have the expansion cap tightened on the bottle to seal it up and allow the pressure/heat to build up

 

Edited by - Nick Chan on 4 Nov 2012 23:45:35

[CharlesElliott]

I took the thermostat out 😬

[charlie_pank]

If the temp gauge says hot but the fan doesn't come on, then the fan's thermoswitch in the top of the rad is either not sitting in water (when cold, loosen expansion cap, then loosen rad bleed screw - does air escape before coolant?), or the thermostat isn't warming up because it's in an air bubble (when cold, remove expansion cap then loosen jubilee clips on thermostat housing then manipulate joints until no mote air escapes)

[Blokko]

Run out of fettling time for now - on a train at the start of another trip to the US.

 

Charlie - the fan does not kick in until the thermostat is open, so sequence of events is temp up to abt 95 with no fan, at which point the thermostat opens, dropping temp to abt 85. Temp then builds again and just over 90 the fan will then operate. Guess it is by design that you would not want the fan to work until the thermostat is open?

 

Nick - might try that method when I get back home. Always assumed that the system had to be pressurised, but then I guess there would be now way for the air to escape.

[charlie_pank]

If what you say is right then the thermostat is opening and closing regularly which shouldn't happen. I'd take the stat out and check its operation then put it back and refill the system, using the bleeding method I recommended to get the air out from around the stat. Do check the radiator bleed as well, as it takes 30 seconds to do and might solve your problem...

[Johnty Lyons]

I've run a K for 15 yrs had engine in and out countless times and Never had a pproblem with cooling.

The secret is in the bypass. Cct itis that link from the head round back of engine to stat that. Controls everything. Get air out of that and hot water from head will open stat and bobs your uncle.

I just cant see why everyonemakes such a fuss abouut something so simple.Rember air migrates to higest poinht and on 99% of Ks that is the bypas hose.

[SLR No.77]

I don't jack the front up anymore ...

 

If not already done, 2 mods need doing to the system, firstly fit a "bleed T" in the highest point of the bypass hose (and make sure you can lift it higher than any other high point of the system), and secondly make sure you've drilled a reasonable size hole in the thermostat (4mm) and fit the stat with the hole oriented upwards.

 

Remove the expansion tank cap and radiator bleed screw and fill the system slowly through the bleed T with the bleed T raised higher than the rest of the system. When the level is up to the radiator bleed screw refit it. When the level is where it should be on the expansion tank refit the cap. Continue filling until it's up to the bleed T and no more can go in then seal the bleed T.

 

Job done.

 

Stu.

 

Edited by - sforshaw on 5 Nov 2012 15:49:55

[Johnty Lyons]

Abso*******lutley its piss easy.

[Blokko]

Thanks for the input everyone.

 

Flew back in from the US of A this morning and spent some more time looking at this. Managed to get some air bubbles out of the rad bleed, but I'm still of the opinion that the temp is running higher than it was prior to the coolant change

 

I think that there are two issues - 1) my mechanical ineptitude 😳, and 2) I think that any air left in the system is in the bypass hose (as per Johnty suggestion) and the crappy jack I have isn't quite getting the car high enough.

 

Gonna scarp the track day and then at my leisure look at one of the more 'permanent' solutions such as bleed valves, PRRT, drilling thermostat etc.

 

Thanks again all

[Malc_Bateman]

As someone who posted a query on the Forum a few days ago on the coolant subject and is planning on doing his first hose & coolant replacement this weekend, the threads on this scare me to death. Some people say it is easy, others not so. Given that the basic design of the "Seven" is old technology why is hose/coolant replacement so fraught with airlocks/difficulty? My 14 year old car is running sweet as a nut, but has perished (minor) hoses near the clips. Am I to find replacing one problem creates a bigger issue?

[Roadsport06]

As already said, get a bleed tee here and fill it up from there. I fitted mine when I built the car after reading about air locks.

[Ozzy]

You don't have to worry, and you don't necessarily need a bleed T. Have a look at Ozzy's easy to follow guide below.

 

All you need is a little patience. Just take your time, and never do anything in a hurry!

 

Here you go.

 

I really don't understand why some people have such a problem with this?

 

In 8 years of ownership, and probably 6 coolant changes for various reasons, I've never had a problem re-filling. In fact, I've done it again this week, as I had to fit a new water rail. I have a heater, but I don't have a bleed tee (never felt the need for one), and all I've ever done is the following:

 

After draining, re-connect all hoses.

Jack up front end as high as your jack will go.

Remove small bolt thingy from top of radiator.

Start to fill through expansion bottle, and continously massage top & bottom rad hoses.

Fill a little more, keep massaging hoses (listen for gurgling sounds, air escaping) let it sit for a few minutes whilst massaging heater hoses.

Fill some more, still massaging rad hoses.

When you've filled the bottom of the expansion bottle, and it won't take any more (don't fill expansion bottle completely), drop front end back to earth, massage hoses, and fill a lttle more until coolant bubbles out of top of radiator hole where the bolt thingy goes.

Screw in bolt thingy, start engine and run up to temp. The top of the radiator should get very hot first, whilst the bottom of the rad is still cold. If this is happening, then you know there's no air trapped in the top of the radiator.

As it heats up, and the thermostat opens, then the bottom of the radiator should get hot, then after a little while longer the fan will kick in. I have an 82 degree stat by the way. Once this is complete, you may need to add a little more to the expansion bottle.

 

That's all I've ever done, and it's worked fine every time.

 

 

 

Edited by - ozzy on 16 Nov 2012 21:18:52

[charlie_pank]

Nothing to be scared of, there's no magic involved, just GCSE physics. The air bubbles migrate upwards, armed with that knowledge you should be able to figure out a sequence of filling and hose-attaching that eliminates air locks.

[Blokko]

After another unsuccessful attempt at filling the coolant, went off to Halfrauds for a new thermostat. Lo and behold, temperature now sits steady just over 80 until I pick up and hold the revs to the point where the fan kicks in for a short period, bringing the temp back down.

 

Will need to take the car for a good run before I'm convinced that the problem is sorted (need to wait for the rain to stop), but signs look good so far.....

 

So maybe the thermostat was the problem all along (cue I told you so comments 😬). Just odd that this didn't seem to be an issue until the point where I changed the hose / coolant

 

Thanks to Phil for the assistance today 😶‍🌫️

[charlie_pank]

You know how to check a thermostat in a pan of water, right?