Cooling Issues

[Cadence]

Hello All,

I noticed my sprint was starting to get pretty warm in slowish traffic a few days ago. Couldn’t stop on the dual carriageway so soldiered on with the heater on max & blipping the throttle to spin up the water pump as recommended in the handbook.

The temp just nudged over 100C at the peak. Noticed that the carbs were then spitting back (?) when at its hottest - fuel vaporisation?
NB I have the standard glass fuel pump.

FYI the car had been to Tom Airey tuning the previous week and the carbs are now spot on. Tom also fitted new iridium plugs. The car gave a strong 136bhp at the flywheel on the Vegantune cams.

Pretty certain the carb upset is heat related as the car started just fine when cool.

I returned home at night when it was cooler / less traffic and it ran OK albeit at around 90C on the M40 at 65mph.

Points to note:

A. The electric fan (working fine previously) had stopped working.

B. Discovered the lower radiator air deflector is missing - replacement on order

C. The expansion bottle remained approximately 50% full

D. Water level in the radiator has fallen to the top of the core I.e. below the level of the otter switch (new last year). No obvious leaks but checking again this weekend.

E. Radiator was refurbished last year with an additional core, so should be sound.

F. No mayonnaise in the oil filler cap or water on the dipstick, so hoping the head gasket is ok.

I’m no mechanic, so here are my dumb questions……….

1. Does the otter switch stop working if not immersed in water?

2. The previous owner told me that the expansion bottle drew water in when needed and got it back when expansion created an excess. Why is the radiator low but there’s still a pint in the bottle?

I was under the impression that if the expansion bottle was at the right level then all was well with the water level.

3. I’ve read somewhere that the air filter housing should be repositioned to increase airflow - if that’s necessary, any pointers on where please?

Your collective advice on how best to investigate would be much appreciated

Cheers

[Pastapesto]

Hi Cadence

I'm no engineer & I am sure you will get a very technical reply soon but a couple of things that might help..... The pipe/hose in the overflow bottle must stay below the level of water/coolant, otherwise it will lose the vacuum effect and suck/leave air in the top of the rad. It would be ideal to cut a slight angle of cut to the end and try to make sure it is very near the bottom of the bottle. On my Sprint, some times when I open the bonnet the front of the bonnet pushes on the hose and this pulls the pipe up slightly. If I dont check it occasionally, it has pulled the hose above the coolant level and so after a drive I have a slight gap of air at the top of the rad. I have got used to checking it before I go for a drive.

And yes, I think that the otter switch needs the contact with the water around it to sense the temperature.... It could all be something as easy as the pipe being too high and getting air at the top of the rad.

Of course, there may be other factors but I have had a similar problem on my car.... Good luck and I hope you sort it quickly....

A

[JonB]

I think PP is spot on there. I was going to say the same.

Fan stopping is the first harbinger of doom for your head gasket. Yes, the otter switch can't measure the coolant temperature accurately unless it's submerged.

When I fill my cooling system (well, the one I had on my +2 before it was sold), I max out the tank then half fill the expansion bottle, ensuring the pipe is submerged. Then any bubbles in the system should be expelled through the bottle when the engine is hot and replaced when it cools (via contraction of the coolant on cooling, creating negative pressure that will suck the bottled coolant back throught he pipe).

As to the intake, it should be easy enough to suss out where to put it so it's not obstructing airflow to the rad. Off to one side, out of the way of the nose cone opening. My S4 is waiting reassembly, whereupon I will see what's possible in that regard.

[oldelanman]

Your radiator cap looks new .. is it the correct type ? It should have a recovery valve in the centre or the coolant will not be drawn back into the rad as the system cools. Also check that the pipe to the recovery bottle is not leaking where it attaches to the neck of the radiator.

[Cadence]

Thank you Gentlemen for the invaluable feedback - please keep it coming as I’m learning so much here.

I’ve started checking the system using the feedback so far. This is what I’ve found to date

1. Not sure if I’ve got the right radiator cap? It’s an Aeroline branded part. Here’s a pic.

2. I removed the otter switch plug and jumped the contacts with the ignition on - the fan started immediately, which is a win.

3. Checked the hoses again and no signs of leakage - slightly tweaked the hose clips but probs OK anyway

4. I found a mysterious piece of circular white silicon sitting on top of the radiator core immediately under the cap ?? Very elastic might be something that was created with a sealant gun. It’s out now

5. The overflow pipe is a tight seal in the bottle lid and has a 45 degree cut at the bottom of the bottle. Seems an air light fit to the radiator.

6. I’ve emptied, cleaned and refilled the expansion bottle to half full.

7. I’ve topped up the radiator with new coolant - it took an alarming 750ml to the bottom of the neck.

I’m off collecting folk from the airport now but will start the car tomorrow to check for leaks and see if the otter switch is working.

A little concerned where all that coolant went

Cheers Howard

[khamai]

No mention of the condition of the thermostat. When was it last replaced and/or checked? May not be opening fully.

Kiyoshi

[Cadence]

It was new last year. It hasn’t been checked yet - first I’d like to verify that it’s the right type

[pharriso]

Don't forget the foam glued to the underside of the bonnet/hood. What you're doing here is forcing cool area through the radiator, rather than around it.

[Cadence]

Thanks for the steer - the foam is in place so the lower deflector plate (unique to the Sprint I believe) should make an improvement when it arrives on Monday

[Stevie-Heathie]

Side post - is Tom okay and back tuning? I spoke to him in April and he had just got out of hospital? If so I’m happy that he’s back on his feet.

Best
Steve

[Stevie-Heathie]

Side post - is Tom okay and back tuning? I spoke to him in April and he had just got out of hospital? If so I’m happy that he’s back on his feet.

Best
Steve

[Cadence]

Hi - yes he was in good spirits and amazing for 84.

He had the car for 24 hours and transformed the drivability of my sprint. It now starts on the button, ticks over nicely and feels so much faster - the fuelling is great across the whole range with much improved top end.

He found another 6bhp but it feels more like 20.

Not cheap at £520 including fuel additive and iridium spark plugs but worth it for the driving enjoyment

[ericbushby]

Excuse me, but there is nothing amazing or unusual about being 84. I`ll have you know there is a lot of it about round here.
Eric in Burnley
1967 S3SE DHC

[Cadence]

[661]

you said you had the heater on max. has this been used in anger since the last time the coolant was changed?
that may account for the extra coolant required as it filled up the heater system