Fan kicking in too late... bottom pipe cold... coolant disappearing... grr!

Hi guys,

It's been 3000 miles since my last confession, I was hoping to relegate myself from posting in this section but... alas no...
I'm gutted to be honest & considering selling for parts as I need something reliable now that I'm in full time work. I'll try to describe what's happening accurately & maybe one of you can recognise & identify the problem.

The temp is rising dangerously close to fuck up zone. I've been plugging in the scanner to get another eye on the temp & over the last week the fan has been kicking in too late. 99 deg or not at all.

Before a 40 mile run to work, I'm having to bleed the system, rad & matrix is always full as is from the rear of the head. The level is low from the top up cap & the small hose from the thermostat housing. This can be rectified by loosening the rad cap, closing the top up cap & the small hose & refilling the rad. Usually the expansion tank has overfilled an inch or so not while running but during the cool down.

During a run the temp needle is usually slow to reach normal 'in the middle' & then not long before it starts rising. It was correcting itself at 96 deg & on the 2nd rise at about 98 deg. The last couple of days it's been rising passed that & I'm having to pull over to cool down & re-bleed before finishing my drive to work.... not good.

The bottom pipe is usually cold or lukewarm & will become hot while switched off as I wait to bleed again before setting off.
I guess it's air locking & not circulating. Maybe thermostat not working or worse, maybe head again   I've checked all the reachable clips & today I'm about to check the thermostat & tweek up the clips under there.

If this sounds familiar to anyone, I'd be grateful of any insights or solutions.

Cheers,

Rdz

I'm reckoning thermostat sticking? Take it out and try without or drill an extra wee hole in it to be safe? So much unreliable shite around with aftermarket components nowadays.

Or its completely f&cked?

The coolant must be going somewhere? I'm assuming you've checked the springiness on the clips?

Yeah it's my 3rd thermostat. I'll pull it out & test it on the stove, the last 2 had stuck closed.

I changed all the clips to jubilee while doing the head.

Logi wrote:The coolant must be going somewhere?

mmm, until the last couple of days what was missing from the system was in the expansion bottle but as it's been getting hotter I've been adding a cupful.

It's not pulling from the expansion bottle at all now where it was before. I wonder if the expansion bottle is sealing. I might try a bit of silicone around the lid.

Don't matter if the tank seals, as long as the hose is below water it'll suck it back in. Drill a couple of wee holes in the stat, it takes a wee bit longer to reach temp and it's not running at 100% efficiency but you can cover the rad if needed, better safe etc esp with a Hijet   

Cheers Logi, I'll get out there now & give it a go & see.

You are right there Logi about the poor quality Thermostats. I have had a number of faulty new Stats and I know HJ has too. Trouble is they will work ok at first ( or sometimes not come to think of it ) and the start playing up then go weeks ok and then suddenly play up.

Going back to the Radcap issue the radcap on the engine needs to be able to let the water syphon back into the system when the engine cools. The First Line Radcap FRC 74 only lets the water out I think so it cant syphon back in again. The ones that allow the water to syphon back have a hollow centre tube to let the water back in and must have a two way valve in it. So presumably there must two listings for the caps. Am I thinking correctly or not ? Seems logical to me. HJ where are you ???

Relative success, it should get me to work this week anyway.

I pulled out the thermostat, tested it on the stove & it worked well, "it opened at 84 deg".

I'd previously drilled 3 small holes in it when I 1st put it in a couple of months ago...
I wasn't happy with it running under temp so I'd blocked them up with wire. So I unblocked 1 hole & refitted it.

I tweeked up all the hose clips while I could get to all of them.

I filled the system & run it up to temp with a short run & ticked it over til the fan kicked in (still 98 deg!) & then let it cool down. The expansion bottle had the cupful over max line so I pulled that out back to max.

I took the filler cap off & it was nearly full but going down slowly, so spent 10 minutes topping it back up an egg cupful at a time. I think I could been there continually filling up for another half hour but I couldn't be arsed so stuck the cap on & took it for run for an hour.

Temp was reading between 75 to 85 deg... mostly nearer 85 with the needle never pointing straight up. No high temp, no fan, even on hills, bottom pipe lukewarm to warm:D .

After cooling down it's the same story with the fill level, so I'm leaving the cap off & popping out to fill it up from time to time.

Conclusion:
The fan isn't getting the right message so a sensor must be faulty. Surely it should cut in when it gets to 88 degs or so? not 98! . But I'm not sure which sensor is communicating with the fan.

Thanks for the quick fix Logi, hopefully I won't be late for work this week.

Woody, these are the ones I have: http://www.ebay.co.uk/itm/1640187Z04000-RADIATOR-CAP-PIAGGIO-PORTER-PETROL-AND-DIESEL-ALL-MODELS-/350925487489?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item51b4c9fd81

Yeah they have the hole running up the centre. They've just got cheaper too, not bad for a genuine part.

If your purging into the header tank by more than 3/4 inch then you have an issue

If your purging into the header tank by more than 3/4 inch then you have an issue