bottom hose cold, thermostat not opening

weller · Post by **weller** » Sat Apr 12, 2014 4:22 am

Hi guys,

I've got a 1995 2.5 TD (WL engine). I've put a new cylinder head, new rad, new thermostat, hoses, cam belt, engine / water temp sensors and fresh coolant in. The system has been successfully bled, the thermostat has been checked out of the vehicle and it opens at 83 degrees. Both heater matrix have been flushed and the water circulates easily around the engine.

When I'm. Driving the vehicle and air is flowing over the engine and radiator, the thermostat will NOT open, no matter how hard I push the engine, even in slow moving traffic with little air to cool the system.

The thermostat will only open when stationary and the revs are held around 2000-3000 rpm.

The water is able to flow arouse both heater matrices as the pipes for these are before the stat, so the heaters are blown hot and the engine temp never goes above half way.

Does anyone have any ideas and can a few of you. Check to see if your bottom radiator hose (under pass side of bumper) gets hot once the temp guage is half way and after a run.

Many thanks,

Ash.

wonkanoby · Post by **wonkanoby** » Sat Apr 12, 2014 8:47 am

nothing sounds wrong to me

wait till its warmer and it will open

Bluespanner · Post by **Bluespanner** » Sat Apr 12, 2014 8:48 am

When I changed my radiator and hoses and started the bleeding process it took a very long time for the bottom hose to get warm/very warm. The best part of an hour using Haydn and Kirsty's method for bleeding on youtube. I was just about to give up when the hose starting getting warm and the funnel started to gush with more air bubbles. Before I changed the radiator the fans would cut in much earlier.
I assume that you followed the bleed process to the letter and the Bongo is otherwise operating normally?? so possibly fitting a aftermarket engine temperature monitor/alarm if you're concerned the engine is getting too hot? The Bongo is temp gauge is next to useless.
Thermostat may have been damaged on fitting if you've ruled out the above.
There's plenty on the forum with lots on knowledge on this subject I'm sure you will have more suggestions soon.

Post by **Simon Jones** » Sat Apr 12, 2014 10:13 am

It sounds normal to me too. Unless you have modified the standard gauge then it will get to about 11 o'clock and just stay there until such time as it starts to overheat. If you want to see if the thermostat is working, get a digital temp gauge with an external sensor and attach it to the bottom hose so you can see it warming and cooling as you are driving. With another gauge on the head you'll also see the temp go up, then the 'stat opens which increases the circulation so the bottom hose will warm up and then the head temp goes down.

haydn callow · Post by **haydn callow** » Sat Apr 12, 2014 12:20 pm

Perfectly normal...a couple of years ago at the Big Bash I checked approx 10 bongo bottom hoses as they arrived, some had driven over 200 miles......only one bottom hose was hot and that was the bongo that overheated on the way home....

mikeonb4c · Post by **mikeonb4c** » Sat Apr 12, 2014 12:25 pm

Bluespanner wrote:When I changed my radiator and hoses and started the bleeding process it took a very long time for the bottom hose to get warm/very warm. The best part of an hour using Haydn and Kirsty's method for bleeding on youtube. I was just about to give up when the hose starting getting warm and the funnel started to gush with more air bubbles. Before I changed the radiator the fans would cut in much earlier.
I assume that you followed the bleed process to the letter and the Bongo is otherwise operating normally?? so possibly fitting a aftermarket engine temperature monitor/alarm if you're concerned the engine is getting too hot? The Bongo is temp gauge is next to useless.
Thermostat may have been damaged on fitting if you've ruled out the above.
There's plenty on the forum with lots on knowledge on this subject I'm sure you will have more suggestions soon.

Sounds like you have a very healthy engine but if you are worried i think the advice above is very good and fitting an engine block temperature gauge should give you peace of mind. It has been known for thermostat s to be fitted incorrectly positioned, but I doubt someone with your obvious competence has done that!

weller · Post by **weller** » Sat Apr 12, 2014 6:07 pm

Hi there guys,

As usual you haven't let me down. Nice to see a wealth of knowledge as appose to guess work. This is the second thermostat I've fitted, with this one being a genuine one, just to be extra safe. The post which details the guy checking 10 Bongo's and all bar one had cold bottom hoses was extremely helpful and reassuring.

Once I've got a bit of spare cash I'm going to get a digital temp sensor. I'm in the process of making a low coolant alarm with a VW golf sensor. I will drill it in to the expansion tank. I will let you all know how I get on.

Ash.

mikeonb4c · Post by **mikeonb4c** » Sat Apr 12, 2014 10:49 pm

weller wrote:Hi there guys,

As usual you haven't let me down. Nice to see a wealth of knowledge as appose to guess work. This is the second thermostat I've fitted, with this one being a genuine one, just to be extra safe. The post which details the guy checking 10 Bongo's and all bar one had cold bottom hoses was extremely helpful and reassuring.

Once I've got a bit of spare cash I'm going to get a digital temp sensor. I'm in the process of making a low coolant alarm with a VW golf sensor. I will drill it in to the expansion tank. I will let you all know how I get on.

Ash.

Goodo. The bloke who looked at 10 Bongos is Haydn, who came up with a really good low coolant alarm for the Bongo. I bought one of the first ones and its behaved faultlessly for 7 years. Reliability is everything with these devices.

The Great Pretender · Post by **The Great Pretender** » Sat Apr 12, 2014 11:19 pm

weller wrote:Hi there guys,

As usual you haven't let me down. Nice to see a wealth of knowledge as appose to guess work. This is the second thermostat I've fitted, with this one being a genuine one, just to be extra safe. The post which details the guy checking 10 Bongo's and all bar one had cold bottom hoses was extremely helpful and reassuring.

Once I've got a bit of spare cash I'm going to get a digital temp sensor. I'm in the process of making a low coolant alarm with a VW golf sensor. I will drill it in to the expansion tank. I will let you all know how I get on.

Ash.

Your topic brought back memories of where I was nearly 7 years ago. Along with many others the mysteries of the cooling system were overcome. Some great reading if you search.
Good luck with the tank, been there got the tee shirt........................

weller · Post by **weller** » Sun Apr 13, 2014 3:00 pm

Hi the great pretender,

In the above image I can see you've fitted what looks like a float switch. What vehicle is it off, or is a universal one. Did you have issues with the baffles in the tank getting in the way?

Ash.

rita · Post by **rita** » Sun Apr 13, 2014 4:00 pm

weller wrote:Hi the great pretender,

In the above image I can see you've fitted what looks like a float switch. What vehicle is it off, or is a universal one. Did you have issues with the baffles in the tank getting in the way?

Ash.

Might be worthwhile considering one of these as a very reasonable alternative, they get a good write up on other forums.

http://www.mdocuk.co.uk/forums/viewtopic.php?t=38102

http://www.ebay.co.uk/itm/Low-Coolant-L ... 27cc0c14ae

haydn callow · Post by **haydn callow** » Sun Apr 13, 2014 5:25 pm

Or even the original one...developed with the help of members of this forum....many thousands of bongos have them fitted......many cylinder heads saved.....proven reliability and after sales back up.
See www.coolantalarm.co.uk

Fitted by most of the main Bongo dealers you will find on this forum

rita · Post by **rita** » Sun Apr 13, 2014 5:55 pm

haydn callow wrote:Or even the original one...developed with the help of members of this forum.. ..many thousands of bongos have them fitted......many cylinder heads saved.....proven reliability and after sales back up.
See http://www.coolantalarm.co.uk

Fitted by most of the main Bongo dealers you will find on this forum

What about the Toyota Hilux guys.

bottom hose cold, thermostat not opening

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