Help - Overheating Srad

[V6Jon]

Afternoon all,

I have noticed over the last month or so my SRAD seems to go from normal temperature to 100+ very quickly if I am sat in traffic, or crawling along a slow speed.

As an example, this morning I rode into work and about a mile and a half from work came up behind an artic that I couldnt get past straight away. I was behind him until I was 100 yards from the office at about 15-20mph, including one complete stop at a roundabout and by the time i pulled into work the temp guage was up to 102 !

It is not a hot day over here today, the coolant system was flushed and refilled with Rockoil Kool last year, and until recently I have not noticed any problems. It is not leaking anywhere so I am not sure where to start with this one !

Is it worth changing the thermostat or rad cap ? cos nothing else springs to mind.

All (well OK, most) suggestions welcome !

Cheers

Jon

[Evilchicken0]

If it isn't losing coolant then you shouldn't need to change the cap. Maybe change the coolant again to start with, if you run the bike (when it's cold) with the rad cap off you should get the air out of the system.

[BudgetBoy]

Does your fan kick in?

If yes..

take rad cap off when cold and start it.. And trapped air will escape.

if its not that id look at temp switch/sender

[V6Jon]

Cheers chaps my thinking behind th rad cap was that it is (I believe) designed to hold in a certain amount of pressure and allow anything beyond this to escape into the expansion tank. If this is not functioning properly this will affect the way the system works ?

Will get the side panel off at the weekend and try running from cold to fan on with the cap off.

Does anyone know how many temp sensors there are in the system ? Is it one for everything or one for the fan and one for the guage ??

Thanks

[Evilchicken0]

Don't run it "to fan" with the cap off. You're circulating the coolant so it moves and air bubbles to the top and venting at the rad cap. When the system is pressurised it boils (or raher doesn't boil) at a higher temp, with the cap off you could boil the coolant without the fan cutting in which could harm the engine.

[lorenzo]

Check your haynes to be certain, but from memory, there's one sender for the temp guage on the thermostat housing then a simple temp controlled switch on the radiator for the fan. With this in mind, I'd be making sure that the whole of your radiator is getting warm, so you can try and suss out if the thermostat is even opening. Obviously, bleed your system by running it with the cap off simply as it's easy to do. You've not said if the fan kicks in or not, if not then you really do need to check your 'stat.

[V6Jon]

Right, the sun is out this morning so I took the scenic route to work which ended with me stuck in stop-go traffic.

I rode about 15 miles at between 30 and 50 mph and the temp was fine, when I hit town and my speed dropped the temp started to rise, as I moved through the traffic the temp moved up and down very quickly depending on whether I was stopped or moving at 20+ mph.

As I got near to work I got stuck in traffic for a couple of minutes and the guage hit 108, and which point the fan kicked in !

When I pulled into the underground car park and trickled through at walking pace the temp climbed again so I left it until the fan kicked in again, waited for the temp to drop again then switched off everything (key out) to see if the fan stayed on, which it did, so . . .

As the bike is warming up quickly I presume the stat is closing.

Similarly, as the fan is cooling the engine I presume the stat is opening to allow the cooled coolant back into the block.

As the fan is kicking in at the correctly indicated temperature, I presume both temp sensors are working normally.

Which I reckon leaves me with a large air lock somewhere, (probably in the radiator) in the system !

Or am I missing something obvious here ??

[dai1984]

I had trouble with my rad cap and its easily tested by taking it to a local bike shop and seeing if it holds pressure on their test kit. I had Coolant spewing out of it which was a good indicator.

I'd also say there may be air trapped in there or maybe the stat is knackered? There's all sorts of reasons why it may over heat including a blocked or damaged radiator or a blockage in the system especially if normal waters been used causing scale to build up.

[MarkB]

I had similar problem with my srad recently. Bike warmed up quicker than normal and just kept on getting warmer on tick over. It started cooling down when riding but fluctuated around 80 - 90`c. Normally temp should be 74`c. Replaced thermostat - problem sorted.

[V6Jon]

Cheers chaps, I have picked up a bottle of coolant today so I can 'burp' the system at the weekend, at which point I will also check (as best I can) and clean the pressure cap.

If that doesnt help I will order a new stat/cap on Monday to try.

[V6Jon]

Right, got an hour in the garage this afternoon and took the side panel off to get at the rad cap, removed that to find the cap is clean, the seals look in good, here are no signs of leaks and the coolant is still clean.

Running the bike up revealed there is no air in the system.

Arse !

New thermostat on its way, will see if that fixes it.

[MarkB]

Jon,

Have you replaced thermostat yet ?

Reason i ask is when i replaced on mine i then took it for mot which is about 20 mile round trip and temp. was fine.

Today, went out and did about 200 miles but temp was fluctuating again. While on the move 74 - 85, in traffic, anything up to 105 when fans kicked in. No leaks and has correct mixture of water/coolant

I ran clean water through rad before slowly re-filling the system with fresh coolant/water so not sure what problem is now.

[V6Jon]

Sounds exactly the same as mine!

Not replaced the 'stat yet, only ordered it last night. Got confirmation it was shipped today (good old Wemoto !) so I am planning on stripping it, flushing everything through and starting from scratch with the new stat.

If that doesn't work not sure what to try next !

[MarkB]

Quite a lot on the net about SRADs running hot but i`ve never had any trouble up to now.

Always ran around 74 - 78`c whatever the conditions.

Went for the thermostat first due to age of bike and not being used over winter.

Same as you - think i`ll start from scratch.

[V6Jon]

Quite a lot on the net about SRADs running hot but i`ve never had any trouble up to now.

Always ran around 74 - 78`c whatever the conditions.

Went for the thermostat first due to age of bike and not being used over winter.

Same as you - think i`ll start from scratch.

A lot of that seems to refer to running lean causing the overheating, and given my 'unusual' exhaust system and the lack of Dyno facilities over here, I am wondering if it's that now.

Jon

[V6Jon]

Evening all,

Jut been out in the garage for an hour and pulled the SRAD apart, these are the things I found :

One of the carb/airbox clamps wasn't done up.

The plugs are not worn and are a nice colour, so that and the way it runs makes me think it is not running hugely lean.

The coolant is clean and everywhere I can see inside the cooling system is spotless.

I changed the thermostat for he new one and refilled the system and that is where I stopped as the wife will kill me if I start it now !

I chucked the old stat in a pot of hot water and it opened, unfortunately I also spotted at this point the temp rating on the new stat was different to the old one. A quick check of the Haynes tells me the new one is about 4deg hotter and out of spec. Bugger.

So from this I suspect I should probably put the old stat back in, and my problem is actually one of the following :

The rad is not flowing enough air.

The pump is not moving enough coolant

The coolant I am using is not up to the job (Rockoil Kool)

As soon as i can. Will run it up again and see what happens, but I am not hopeful.

Jon

[thefatman]

You've not filled it up entirely with antifreeze have you?

It needs to be diluted with water.

If you run entirely water it cools better as water has a higher specific heat capacity than antifreeze. But it boils over at a lower temp, maybe 115 rather than 125.

Are the fins of the rad reasonably clear, mud thrown up from the front wheel can block them.

Have you checked the tempearture sender/gauge to see that it is working correctly?

[BudgetBoy]

You didnt dilute the rock oil Kool did you? You put that straight in as it is, i use it all the time and never had a problem (its a nice orange colour now instead of the old blue)

And when you tested the old thermo did you have a thermometer to make sure it was opening at the correct spec, and vice versa?

Are your rad fins all clear?

Are your A/F mix correct on your carbs? what year/cc is your bike and i will have a look for you.As this can make it run hotter.

[thefatman]

Sorry my mistake, i've not used rock oil kool didn't realise it was pre-mixed.

As I said though coolant doesn't matter to the cooling efficiency, any brand or plain old water won't really affect the temp it's running at as long as you haven't used undiluted coolant that isn't pre-mixed.

[V6Jon]

It is filled entirely with Kool, not diluted.

The rad fins are not too bad, and reasonably clean, certainly better then the second hand ones on eBay !

It has two temp senders, one for the guage and one for the fan, they appear to be ok as the fan kicks in at the right temp on the guage (107 deg) and I have no doubt it is running hot, once it gets past about 95 degrees it feels different to ride if you know what I mean.

It is a 96 SRAD 750, and unfortunately I don't have a thermometer.

Not sure on the mixture, though as mentioned the plugs look a good colour and it feels ok to ride.

Thanks for your help guys.

Jon

[lorenzo]

Jon, I am right in thinking that you swapped exhausts to a Ti one off a thou, yes?

[BudgetBoy]

Your settings on your carbs should be as follows.(the main ones you will need anyhow) Always better to go on the richer side rather than the lean side of things.

Main jet 1 & 4 127's

Main jet 2 & 3 125's

Idle jet 12.5

Pilot screw should be 2 turns out

Float level 7mm +/- 1mm

And heres some other stuff..

Plugs should be NGK CR9E or Denso U27ESR-N 0.8-0.9 gap on both

Idle should be 1200rpm +/- 100

Oil should be 10/40w (3.5ltrs)

Coolant 2.5 ltrs

To try and put this to bed i will give you reasons why it does what it does.

1.) its normal, some bikes (like my old zx6r) run hot in slow moving traffic and the fan kicks in (from my experience)No wind through the rads means it gets hot,get going again and it drops the temp.

2.) Something wrong in the cooling system (Coolant level low,leak,rad cap,faulty thermostat,water pump faulty,rad fins blocked,fan not working.

3.) Spark plugs fouled,incorrect plugs,faulty HT coils

4.) Fuel air mix wrong (air filter,pilot blocked,fuel pump faulty,carb intakes faulty/damaged)

5.) oil level low

6.) Wrong end can/modified causes engine to run leaner and carbs need a rejet. (This might be your problem if you have done this.)

Go through some of these and see. diagnostics over the interweb is/can be hard at times lol.

[V6Jon]

Yes Loz, I have got 1000 headers on mine along with a straight through Arrow can, when I fitted the 1000 exhaust I had the carbs ultrasonically cleaned (by Kin Useless of these parts) with new o-rings, float heights and everything returned to stock and new jets fitted.

The standard jets are 127.5 mains on 1 & 4, 125 mains on 2 & 3 with 12.5 pilots all round,

I changed mine when that was done to 130 mains on 1 & 4, 127.5 mains on 2 & 3 and 15 pilots all round.

The bike feels fine to ride, and as mentioned the plugs seem fine.

Thanks for the clues Budgetboy, the carbs have just been balanced, oil and coolant are fine and so is the tickover, reading through the other stuff :

1) I am starting to wonder this, or possibly the system is marginal from new and now its 17 years old . . . .

2) Going to get a thermometer to check the 'stat and rad cap to swap over today along with another flush of the system. That only leaves the water pump.

3) Going to switch the plugs today too while i am in there.

4) unlikely I think given previous work.

5) oil / filter is fine

6) Possible, but difficult to check given the lack of dyno's locally.

WIll try to get the plugs, rad cap and a thermometer today flush everything out again and see where we are.

Thinking about the water pump, is there any way of checking it ? or do they fail in the same way as a car and just start dripping water ??

Thanks for your help guys,

Jon

[BudgetBoy]

Water pumps either work or not (in my experience). Take the rad cap off and look inside.If the fluid is moving the pump is working.

My guess is once you have re-bled the system,fitted new plugs and gone for a nice ride it should be ok. As long as the fan is icking in and drops the temp back to the correct level i would not worry too much. As i said my old zx6r used to do it at lights & in slow traffic.

[V6Jon]

An update of sorts !

My new rad cap turned up the other day so I dragged my arse out to the garage last night for a couple of hours.

I removed the rad, flushed the system and rad out and inspected the state of the fins. There are a few damaged areas but nothing major, and due to the low mileage and lack of year round use the fins are not clogged up with crap. Having got out before the sun set I held the rad up and was able to see light through about 90% of it !!

I have refitted the rad with new rad cap, coolant and thermostat, and as mentioned earlier I also stuck in a new set of plugs although the ones already in there were the correct type and appeared to be fine.

At this point I had to stop as the next step is to run the bike up to 'burp' the coolant system, check that I can see the coolant being circulating by the pump and to check for any leaks before putting on the bodywork.

The combination of a five year old and a race pipe mean this unlikely to happen before the weekend, but I am determined to have it ready for a couple of test rides during the beautiful weather the (lying bastard of a) weatherman is promising for next !

Jon

[V6Jon]

The inside of the entire cooling system is pristine !

When I bought the bike and stripped it down the only thinkgs that didnt appear to have been negected was the correclty adjusted and well packed head bearings and the cooling system which was imaculate and filled with fresh clean coolant.