Transmission fluid in cooling system 2.5 Diesel Auto 1999

[Gasy]

300 psi is 20 bar
No chance of that pressure there
You'd blow the rubber hoses

[rita]

300 psi is 20 bar
No chance of that pressure there
You'd blow the rubber hoses

I think you have read it wrong, we are talking about the pressure at the rad ( ""The ATF pressure at that point will be a least Twice as much as the coolant pressure""and the pressure that can be produced INSIDE the box to operate the various components which because it is harnessed wont come up the dip stick..

[Simon Jones]

Presumably, AFT pressure is only maintained while the pump is being driven by the engine so once switched off, the pressure will soon drop off. At the same time, the pressure in the cooling system will remain present until the temperature has returned to ambient which could be many hours later. During that time, it would seem likely that coolant would make it's way into ATF through defective oil cooler thanks to simple difference in relative pressure.

If it were me, I'd be draining, cleaning & refilling both systems to minimise chances of contamination.

[rita]

Presumably, AFT pressure is only maintained while the pump is being driven by the engine so once switched off, the pressure will soon drop off. At the same time, the pressure in the cooling system will remain present until the temperature has returned to ambient which could be many hours later. During that time, it would seem likely that coolant would make it's way into ATF through defective oil cooler thanks to simple difference in relative pressure.

If it were me, I'd be draining, cleaning & refilling both systems to minimise chances of contamination.

Yes simply that's what happens .

[mikeWalsall]

The plastic radiator top can 'pop off' but never heard of the lower part .. even then .. unless somehow there was internal damage .. how would coolant get from the radiator into the oil cooler compartment ..??

[Gasy]

I had a pressure gauge in my ATF rubber hose from ATF box to rad and it only got to 1 bar when hot and at full revs
The pressure to the rad changes with revs but sits at about 3/4 of a bar in normal use

[Simon Jones]

I guess what I'd do is disconnect & plug up both the ATF pipes from transmission then block one of the pipes in the bottom of the rad & then pressurise the other one with a car foot pump (or similar) with a pressure gauge. Pump it up to say 20 psi, see if it holds the pressure for an hour or so. You could also remove the rad cap (which will loose a drop of coolant) & then check for any bubbles being introduced from the pressurised oil cooler.

Interesting point Gasy about your readings. 1 bar = 14.5 psi so pretty low and very similar to the level which the coolant system runs at. I guess the 300psi figures mentioned are contained with the guts of the gearbox so don't make it out to the oil cooler.

[Gasy]

Yep at cold and on tick over it hardly pumps oil at all
I only starts to increase pressure with temp and then it's rev related
The more revs the more it pumps and increases pressure
But will only reach 1 bar when hot and at full revs
At tick over it was about 1/3 of a bar

The coolant pressure must be just under 1 bar at full temp
As blows cap at 1.1bar
So radiator coolant pressure will be greater at rad than ATF pressure
The majority of the time

[Simon Jones]

So, maybe it's not ATF after all? Radweld was mentioned earlier as being a possibility but that seems unlikely as its only just appeared. I've used Radweld in a previous car and it's very hard to use undetected as it turns the coolant a lovely rusty brown colour. I ended up flushing it all out again as it just looked like the cooling system was in a dreadful state.

If it's perhaps not ATF then the next most likely explanation would be engine oil. Possible sources: head gasket, oil cooler or turbo. It may be worth sending a sample of coolant off for analysis to see if the chemical composition can be determined. It is quite common to send oil samples for this type of test as it can tell a lot about the condition of the engine in much the same way as a blood test does for us.

It would be interesting to hear if there are any other symptoms in addition to this potential contamination. There was mention of an overheating incident: has the source of this been traced? Could it just be crud in the bottom of the rad that caused the over heating and now it's been flushed, the sediment has been disturbed.

[Diplomat]

The plastic radiator top can 'pop off' but never heard of the lower part .. even then .. unless somehow there was internal damage .. how would coolant get from the radiator into the oil cooler compartment ..??

I would imagine that the bottom of the rad is considerably cooler than the top, thus giving the lower seam a longer lease of life. This could be a blessing as leakage down there is more difficult both to sea and to seal.


Frank

[Douglas]

Thanks all. Seems new rad needed as the system has been flushed, clean water in, run up to temperature but oil still appears. May then be a head gasket issue, as the pressure is high, per garage. Does that make sense? Also any idea what cost for a new rad - is there one from a mainstream vehicle would suit to cut costs?

[mikeWalsall]

Look on ebay .. pattern part rads are around £50 ..

http://www.ebay.co.uk/itm/MAZDA-BONGO-2 ... 4424&rt=nc

Cylinder heads supplied / fitted considerably more ..

[teenmal]

You could get your garage/mechanic to do a pressure test on the oil cooler that would prove a point and take out some of the guess work.

[helen&tony]

Hi
Ian has 2 types of rads in the club shop...both tried and tested!
I prefer all-metal ones...BUT...I have an external oil cooler and, quite frankly, the cooling on the Mazda original is most likely better than many of the replacement parts, as I suspect the actual cooling tubes are larger on the Mazda. I shall be putting a Mazda original on this year, although the one I have now (all metal) is perfectly fine, but I might move to Spain, and it's a long journey in the heat down through Greece ,up through Italy, across the South of France, and down to Andalusia...towing a trailer!
Cheers
Helen