Overheating Again!!

trevd01 · Post by **trevd01** » Sat Mar 31, 2007 11:21 am

Taxiback wrote:I think the thermoswitch to switch on the electric fan is at the rear of the block just above the hose to the rear heater above the starter motor.

Taxiback - second time of asking - you must reduce the size of your pics

Even on my 1680 x 1050 screen, they are too wide, and causing this thread to be difficult to read.

Your picture is 2560x1920 -much wider than 99% of screens.
Go back to image shack and change your picture size to 640x480 'message board'.

(Admin)

Thanks, Taxiback, job's a good un.

alphabetter · Post by **alphabetter** » Sat Mar 31, 2007 11:30 am

Dannyboy wrote: Where is the thermoswitch to switch on the electric fan
Duncan

Taxiback has stolen by thunder here, but as I've done the photo here is the same sensor with the engine assembled (page 74 of the service manual if you want to check yourself). The sensor is the thing in the light circle in the middle.

In fact this isn't a simple thermostat, but a temp sensor that controls the fan through the Engine Management Unit. Fan turns on at 108C

Taxiback · Post by **Taxiback** » Sat Mar 31, 2007 11:59 am

trevd01 wrote:
Taxiback wrote:I think the thermoswitch to switch on the electric fan is at the rear of the block just above the hose to the rear heater above the starter motor.
Taxiback - second time of asking - you must reduce the size of your pics

Even on my 1680 x 1050 screen, they are too wide, and causing this thread to be difficult to read.

Your picture is 2560x1920 -much wider than 99% of screens.
Go back to image shack and change your picture size to 640x480 'message board'.

(Admin)

I have resized it just for you hope you have bloody good eyes because I cant see or read anything now and so will 99% of people looking at it now.

francophile1947 · Post by **francophile1947** » Sat Mar 31, 2007 12:25 pm

Taxiback wrote:
trevd01 wrote:
Taxiback wrote:I think the thermoswitch to switch on the electric fan is at the rear of the block just above the hose to the rear heater above the starter motor.
Taxiback - second time of asking - you must reduce the size of your pics

Even on my 1680 x 1050 screen, they are too wide, and causing this thread to be difficult to read.

Your picture is 2560x1920 -much wider than 99% of screens.
Go back to image shack and change your picture size to 640x480 'message board'.

(Admin)
I have resized it just for you hope you have bloody good eyes because I cant see or read anything now and so will 99% of people looking at it now.

Let's not turn this into a "bitching" match!

Trevor was only asking that the photo complied with the site rules and the photo IS now too small, but the original was ridiculously large!! Simple answer would be to take a photo of the relevant area, and not the whole engine bay - it would then have been clear at 640x480.

Taxiback · Post by **Taxiback** » Sat Mar 31, 2007 3:56 pm

Take a picture of the relevant area only and all you get are people asking where that part is in relation to everything else.
I know the pictures are large but you can just scroll past it if it is of no interest to you.

mobyfix · Post by **mobyfix** » Sat Mar 31, 2007 6:30 pm

As suspected the "clever japs" have put a thermoswitch on the block so it turns the fan and cools the already cold radiator ...how useful !! It makes more sense to fit it to the radiator.....

So we don't learn anything more about the overheating problem in question .... but we all learn a bit more.

Thanks

grumpo · Post by **grumpo** » Sat Mar 31, 2007 6:33 pm

I am still of the opinion that the cooling system is NOT "Strange".

The bypass circuits during cold weather are sufficient to keep the engine
below critical temperature and allows the cab heaters to reach working
temperature more quickly, especially if you need to demist the windscreen.
When the return temperature from the cab heating and other bits and
pieces exceeds 80 degrees C, then the thermostat opens to allow water
to flow through the main radiator.

Science is truth, facts only confuse the issue.

Vanmanerik · Post by **Vanmanerik** » Sat Mar 31, 2007 6:45 pm

OK Grumpo, I can go with that theory.

Either the cooling system is :-
a) quite happy using the bypass circuit, heater curcuits and the turbo charger cooling curcuit to keep the engine at its correct working temperature.

b) Or the cooling system is working as we expect and the coolant is flowing through the radiator and back to the engine - if this is the case then I would have expected the bottom pipe to have felt slightly warm at least.

So I assume the scenario is that the cooling system is quite happy as in a) and if the engine overheats then the thermostat would open and bring the radiator into action to cool everything down to working temperature.

But I think the first warm day we get we should all check to see if the engine gets hot enough to activate the thermstat and send the coolant through the rad.

grumpo · Post by **grumpo** » Sat Mar 31, 2007 6:50 pm

I'm quite prepared to buy everyone at the main Bongo bash a pint if
you all prove me to be wrong.

( That's if you can find me of course. )

Vanmanerik · Post by **Vanmanerik** » Sat Mar 31, 2007 7:14 pm

So the Bongo bash is in the summer, as we all arrive we will have to have an independent adjudicator feeling our bottom hoses, if the majority are cold the its 'Find Grumpy', if the majority are warm its ' I always thought Grumpy was right anyway'

In the mean time when someone is overheating what advice can we give.

We could really do with some-one who is able to check out the bypass circuits for crud etc having a touch of the overheating and reporting back to tell us if they were clogged was it difficult to clean them out and did it cure the problem..........

mobyfix · Post by **mobyfix** » Sat Mar 31, 2007 7:21 pm

I agree that there is nothing "strange" about this system... It is fairly logical......the only silly bit is the thermoswitch.... but it is workable as long as there is no fault on the sytem..

This thread is about a particular overheating problem and trying to find the cause... it is a fantastic way also to understand a cars heating system as it is extremely useful to all of us who own one these vehicles.

The thermostat on the bottom hose is a little unusual but common in some makes of car like volkswagon.

I hope we will find out where the fault is eventually so we all learn... we all think we have an idea of what or where the fault is....

We should really have a poll to see who votes for where you think the fault is before we find out the truth.. can we do polls on this forum ?

Dannyboy · Post by **Dannyboy** » Sat Mar 31, 2007 9:52 pm

I'll bring you all up to date.

Earlier in the week I took the garden hose to the cooling system. Took off the top radiator hose and hosed into it, through the engine and back through the radiator. Did the same for the bottom hose. hosed out the radiator from all possible directions. Disconnected the hose from the thermostat to the heater matrices and hosed into it through the engine and also into the pipe leading to the heater matrices then the engine.

Last night I took off the alternator to get access to the hose behind it that leads from the top front of the engine to the top of the thermostat housing. Hosed through the engine and out of the thermostat, then through the thermostat and out of the engine. Then removed thermostat housing to check it. It seemed fine, no blockages and quite clean. All water seemed clean. No sign of a blockage anywhere.

Refitted a new thermostat, filled the system and bled it as per the manual. For the first time ever with a new thermostat my lower hose became hot. Positively hot, enough to be unable to touch the metal return pipe where it joins the thermostat housing. This was while the bongo was stationary of course. The thermostat was obviously open.

Took it for a drive. Covered over 20 miles, partly town, partly country. Temperature guage steady at about the 11.30 position. The lower hose was very hot when I started drive but was cool or cold when I returned.
I was happy. I had solved my problem. I didn't know how, but it was solved.

Went out this morning. Warmed car up and took it for a run. The lower hose did not warm up even though the fan came on. The fan comes on to cool the engine, but if there is no flow through the radiator the fan will not be effective. The hose stayed cold, but it was very hard and clearly pressurised. The temperature guage went way passed 12 o'clock. Overheating again.

I must say I'm a bit puzzled so its back to the drawing board. My next move is to remove the radiator and get it flow tested. I'll keep you posted.

bongoing-mad-simon · Post by **bongoing-mad-simon** » Sat Mar 31, 2007 10:35 pm

hi dannyboy
sorry to see it over heated again, hope you get it sorted soon . i know how frustrating it is, keep going it will be worth it in the end , it will eventually be fixed .

_________________

simon

I'm bongoing mad R U?

Harry · Post by **Harry** » Sat Mar 31, 2007 11:15 pm

Sounds almost as if you have a pinhle leak that is allowing air in when things col down and contract.

Starting up from cold...airlock in system from shutdown but because engine is warm/hot..pinhole leak seals itself.

Now I want to make it clear I'm not an engine mechanic..but I was (in the 70s)an RAF Airframe technician specialising in Hydraulics ans Pneumatics and this sort of intermittant fault was common and bloody hard to diagnose.

Good luck

H

Overheating Again!!

Cold Pipes

Overheating