Overheating? Shall I panic now?

haydn callow · Post by **haydn callow** » Sun Mar 16, 2008 11:49 pm

I think you have it spot on Dandy....
Those who think they drive around with a closed stat must be wrong. If you think about it...if your stat is closed then you have no coolant cooling at all. What coolant you have "trapped in the engine and head would start boiling very quickly...air flow over the engine would not be enough....heater rads would have no effect on the engine coolant as it is not circulating (co's the stat is closed) the heater pipes are to small to pass enough coolant to affect the engine temp. Thats my theory and I'm sticking to it unless you can convince me different..
Top hose hot.. bottom hose warm Rules o.k.

haydn callow · Post by **haydn callow** » Sun Mar 16, 2008 11:53 pm

TGP.. good point....Could it be the stat gets the 82 C from above rather than below??

The Great Pretender · Post by **The Great Pretender** » Mon Mar 17, 2008 12:05 am

haydn callow wrote:TGP.. good point....Could it be the stat gets the 82 C from above rather than below??

If the bottom of your engine is at 82c what temp is the head?

Are your readings of the head from metal?

haydn callow · Post by **haydn callow** » Mon Mar 17, 2008 12:20 am

Temp readings from the head metal.
I understand what you are saying...But.... I cannot put my hand into water which is 82c....I can hold my bottom hose tightly for as long as I want after running 200 miles with a c'van behind. My cylinder head is at around 90c whilst all this is going on. This is not just my Bongo but all I have tested to date...all are much the same. I belive mine is running well and as it should be.....
Wish I hadn't said that.....Sods law about to drop on me

dandywarhol · Post by **dandywarhol** » Mon Mar 17, 2008 12:26 am

The coolant will still circulate through the bypass system until the thermostat is ready to open. There will be a certain amount of heat transfer through the stat and housing to open it - but only when the temp reaches 82.

The lower hose might only feel warm at the radiator but it's been pretty well cooled by that time due to the surface area of all the pipework and radiators. It's quite far forward of where the real heat is - at the head/stat area which will be doing as it's designed to do - as long as the system is operating properly and not gunged up with 12 years of crud.

As long as the lower hose has some heat in it then it must be circulating coolant through the stat. No heat means it's closed and that's apparant when you bleed the system - you need to be sitting stationary/fans off at 2500+ rpm to get the system hot enough to open the stat fully - then you feel the bottom hose as very hot.

I climbed over 2000 ft in a few miles in low gear and at the top of the pass my lower hose was just warm - never had an overheating problem anytime.

The Great Pretender · Post by **The Great Pretender** » Mon Mar 17, 2008 12:38 am

francophile1947 wrote:Your engine should run at the same temperature in summer or winter - that's what the thermostat is for.
The hottest my bottom hose has ever been was lukewarm - there is a feeling that most of the cooling is actually done by the heater radiators.

Now that is half way there, the water runs through the heater pipework bypasing the return from the rad. If the stat dosnt get to 82c and haydn has lots of Bongo's that dont as the bottom hose is warm the problem must be in the header tank

dandywarhol · Post by **dandywarhol** » Mon Mar 17, 2008 12:42 am

TGP - a warm bottom hose must mean the coolant is circulating - through the thermostat surely

The Great Pretender · Post by **The Great Pretender** » Mon Mar 17, 2008 12:55 am

dandywarhol wrote:TGP - a warm bottom hose must mean the coolant is circulating - through the thermostat surely

You decide, the stat only opens at 82c...............so?
And dont call me shirley...........

dandywarhol · Post by **dandywarhol** » Mon Mar 17, 2008 12:57 am

.........so that's when it opens

82 isn't very hot - the system will run happily at 105 or so..................................

Shjrley

The Great Pretender · Post by **The Great Pretender** » Mon Mar 17, 2008 1:02 am

dandywarhol wrote:.........so that's when it opens 82 isn't very hot - the system will run happily at 105 or so..................................

Silly Boy....................82 is at the return

Shjrley

dandywarhol · Post by **dandywarhol** » Mon Mar 17, 2008 1:12 am

I don't get the discussion TGP

As soon as the stat "detects" 82 deg, the stat will start to open, whether it's from the returning coolant or heat transfer through from the other (head) side or a combo of both - it really doesn't matter where it detects it from it just opens when the designers designed it to do so.............before that magical 82 is reached the coolant circulates via the bypass valve at the other end of the stat.
When the stat is closed the bypass part of it is opened, when the stat is open the bypass is closed off.

......anyway, as Zebbidee said................hasta manana.

The Great Pretender · Post by **The Great Pretender** » Mon Mar 17, 2008 1:30 am

http://www.igmaynard.co.uk/bongo/forum/ ... 339#174339
explane how the bypass if it has one works please dandy

The Great Pretender · Post by **The Great Pretender** » Mon Mar 17, 2008 1:32 am

if the return is not hot, the stat is closed

dandywarhol · Post by **dandywarhol** » Mon Mar 17, 2008 1:44 am

I can't remember if we ever got a consensus on this diagram by alpha but it does show the bypass circuit above the stat

The Great Pretender · Post by **The Great Pretender** » Mon Mar 17, 2008 1:56 am

dandywarhol wrote:I can't remember if we ever got a consensus on this diagram by alpha but it does show the bypass circuit above the stat

What is called an expansion tank is in reality if the system worked correctly is a degassing tank to remove air.