ANOTHER OVERHEATING BONGO, HOPEFULLY SORTED

haydn callow · Post by **haydn callow** » Thu Apr 05, 2007 8:00 pm

jamesnjane... when bleeding the system you need to get the bottom hose warm co's that means the stat has opened and trapped air can escape..it does not always rise up through the little hole provided

Peg leg Pete · Post by **Peg leg Pete** » Thu Apr 05, 2007 8:01 pm

hole in the stat is tiny, would not let much water flow.

Peg leg Pete · Post by **Peg leg Pete** » Thu Apr 05, 2007 8:02 pm

I think I read that the hole is to let trapped air escape

Jamesnjane · Post by **Jamesnjane** » Thu Apr 05, 2007 8:03 pm

yes but so are the holes iv added but the difference is clearly visable

Jamesnjane · Post by **Jamesnjane** » Thu Apr 05, 2007 8:04 pm

could be

Peg leg Pete · Post by **Peg leg Pete** » Thu Apr 05, 2007 8:04 pm

Then that means you are letting water through to the radiator to increase cooling effect

haydn callow · Post by **haydn callow** » Thu Apr 05, 2007 8:06 pm

if stats were ment to have holes in them they would come like that. If you have to resort to this then there is a underlying problem. There are thousands of bongos running around for years with no overheating

francophile1947 · Post by **francophile1947** » Thu Apr 05, 2007 8:06 pm

peter humphrey wrote:hole in the stat is tiny, would not let much water flow.

But it might just be big enough to let enough through to stop the hose freezing. There was a posting on another thread that said that it was surprising how much water passed through the little hole, but I can't find it.

Veg_Ian · Post by **Veg_Ian** » Thu Apr 05, 2007 8:07 pm

Hmm I'm finding it hard to accept this idea of the rad not playing an active part in cooling unless under stress, although your logic is good Haydn. Having a lot of experience with the Toyota Townace cooling system which was the achilles heel of the vehicle, I can report that it also had the stat mounted in the bottom hose. However, the difference here was that the rad is mounted 'in board' and not up front so airflow was very important (and is the same in the lucida range also). I used to have two stats to assist with cooling which I changed over in October and April. My winter stat was the standard stat but the summer one I drilled 2 x 3mm holes into the rim to assist with coolant flow. You lot have obviously latched on to the same idea. In summer of course it is no big deal if it takes longer to heat up as you don't use the heaters. However, I'm amazed that the Bongo appears to suffer in the same way because the rad is mounted up front as it should be. Therefore the thing in common with the Toyota setup and the Bongo would be in its origin - the Japanese home market and the likely 'silting' up of the coolant pathways in the head. I believe someone earlier touched on the idea that maybe the antifreeze used in Japan isn't quite up to the job.

So I'm guessing then the ideal is to have perfectly clean pathways in the head which means regular and efficient cleaning of the system. The state of the rad plays a minor part so backflushing the rad isn't the be all and end all to flushing the system. It would infer the head should be chemically flushed? Drilling holes in the stat assists with coolant flow so is also a worthwhile modification. Does that theory add anything to the picture or make things worse?

Harry · Post by **Harry** » Thu Apr 05, 2007 8:08 pm

Pretty logical that you need to get the engine warm/hot enough to open the stat as the bottom hose/rad has got to be a prime site for airlocks.

Got to point out that I'm basing my opinions purely upon experience of our Freda and as an ex hydraulic/pnematic specialist....I am not an engine technician.

H

Jamesnjane · Post by **Jamesnjane** » Thu Apr 05, 2007 8:11 pm

i agree haydn but i still cant help thinking the bongo wasnt designed for 70+mph long motorway journeys so to over come this i feel adding a few holes to the stat uses that great rad, but i do agree mine was running for year no probs, but the first instant of overeating happened the weekend i lent my dad the bongo and hes a got a heavy right foot.

francophile1947 · Post by **francophile1947** » Thu Apr 05, 2007 8:11 pm

haydn callow wrote:if stats were ment to have holes in them they would come like that. If you have to resort to this then there is a underlying problem. There are thousands of bongos running around for years with no overheating

Agreed Haydn, it's just that we don't seem to be able to establish what the underlying problem is. There have been cases with heads and radiators replaced and they work fine for a few weeks before overheating again - it's just weird!!

haydn callow · Post by **haydn callow** » Thu Apr 05, 2007 8:12 pm

there was a theory that overheating could be caused by the bypass circute being blocked. this could be right but a simple way to check is to see if expansion tank is hot. If it is then bypass is ok co's this is the only input to the tank.

Peg leg Pete · Post by **Peg leg Pete** » Thu Apr 05, 2007 8:13 pm

Veg Ian are you are saying that the radiator plays a significant part in cooling the system?

francophile1947 · Post by **francophile1947** » Thu Apr 05, 2007 8:16 pm

Just the opposite Peter! - "The state of the rad plays a minor part so backflushing the rad isn't the be all and end all to flushing the system."