Engine temp rise after shut-off

[llitvack]

Hi folks.
I have a new issue that I hope someone can help with:
My van usually drives along nicely, with the engine temp generally sitting between 87-90 degrees (according to Haydn's life-saving Alarm). Very occasionally, on long journeys, the temp rises to 95 or 96, but then reduces after some minutes. If I drive 500 miles, the level in the header tank goes down a bit, and I need to top it up, but I can see no puddles on the driveway. I wonder if I might need a new header tank pressure cap (do these wear out?)?
Recently I have noticed, on short journeys, that there is the occasional temp rise AFTER I switch the engine off: it goes from 87-88 (with the van running) to 95 while I'm in the shop. When I turn the van on after 10-15 minutes, and start driving, the temp falls back to its normal 87-90.
I wonder what causes the temp to rise after shutting the van off?
I have not bled or flushed the cooling system in a number of years. My mechanic says to leave it alone if it isn't problematic.
I was thinking about replacing all the coolant hoses and header tank cap this winter; but perhaps that is overkill?
Good wishes from Leon

[Bongolia]

The coolant loss needs investigating asap.
Take it to your garage and ask for a pressure test and a UV dye. That should find it.
Yes the caps do wear out. simple job make sure its the correct rating, not sure what that is for your motor.
The temp rise is not umusual as the flow around the engine has stopped and the coolant will no longer be flowing through the radiator or being cooled.

[Bob]

Agree with Bongolia, but not your garage.

Coolant should be changed (2 years for blue, 5 for pink) as the corrosion inhibitor stops working. This is really impotrant on an engine with an iron block and alloy head.

Flushing also removes sludge from the system.

As said, temp rise when you stop is normal, the heat from the block contiues to be dumped into the coolant and it returns to normal quickly once you start off.

And do investigate the leak, you're regret it if you don't.

[cmm303]

Depends what sort of level drop you are experiencing.
Mine would always drop a couple mm below the max line but never any further. I don't think this behaviour is cause for alarm. However it stopped happening after a new cap, new thermostat, new pump and new coolant so couldn't say which component fixed it.
A continuous level drop over time needs fixing.
If you suspect the radiator cap, locate the end of the black pipe which attaches by the cap, stick this in a small bottle and see if it collects any coolant.

[Bongolia]

Depends what sort of level drop you are experiencing.
Mine would always drop a couple mm below the max line but never any further. I don't think this behaviour is cause for alarm. However it stopped happening after a new cap, new thermostat, new pump and new coolant so couldn't say which component fixed it.
A continuous level drop over time needs fixing.
If you suspect the radiator cap, locate the end of the black pipe which attaches by the cap, stick this in a small bottle and see if it collects any coolant.

That`s a useful tip.

[llitvack]

Hi folks. Thank you for all the suggestions.
For now we are going to go with the following:


- perform pressure test on cooling system
- replace header tank cap
- change coolant and add a K-seal type additive
- make sure to purge air from system (with seesaw procedure)

If that doesn't work we shall see about changing the hoses.
Should the radiator cap be changed at the same time as the header tank cap?

Good wishes from Leon

[Northern Bongolow]

hi leon, the rad cap is just a bung to seal the rad it doesnt act as a vent or anything, as long as the cap is on tight its fine.

[Bob]

This is only my view, but if there is a leak then find, and fix the leak.

Replace coolant in line with service schedule.

Radiator addatives are very likely to cause far more problems than they solve on a Bongo, but I am not a mechanic...

Good luck.

[Diplomat]

hi leon, the rad cap is just a bung to seal the rad it doesnt act as a vent or anything, as long as the cap is on tight its fine.

Also, bear in mind that if you replace the radiator, don't throw away the 'bung' with the old radiator. My new radiator came without any cap.


Frank

[Northern Bongolow]

if you pressure test it and it doesnt turn anything up it maybe the water pump again leon, when they leak they are usually small regular amounts and are hard to detect.

but you have been here before mate havnt you.

[llitvack]

Hi Ady.
Yes: I have been there before, and never want to go back! The new engine head put a permanent pain in the wallet!
Cheers from leon

[llitvack]

Well, I got the coolant changed, thermostat replaced, and system bled.
All seems to be running fine, except that now the engine running temperature is higher than before.
According to Haydn's Temperature monitor, the running temperature on my Bongo used to sit between 86 and 88 degrees, with some rises to just over 90 if the engine is working harder. Now the engine runs at 91-95 degrees, which is worrying me! Occasionally it climbs to 97, but does not go any higher.
Should I be worried? I have taken the van out on a few runs, and don't want to blow the head! I have not got any long distances, and don't want to do so until I have confirmation that it is ok for a Bongo engine to run at 95 degrees.
Comments, please.
Good wishes from Leon

[mikeonb4c]

I may have missed it, but i can't see in your posts that you have fitted a replacement radiator. Are you confident it has good flow through it as it is a key component and the weakest link will largely determine the performance of the chain (as it were). The heater radiator circuit is i think said, in a Bongo, to contribute to cooling also. Does you front radiator blow nice and hot even on full heater fan?

[teenmal]

Sounds like Radiator and or Water pump fault. But make sure that your temperature gage is in fact now accurate .

[cmm303]

Was it a genuine Mazda thermostat or a pattern part? If a pattern part, maybe it is operating at a different (higher) temp.