Tiny Bubbles in Radiator What to do Next

[Thor454]

Hi fellas,

I've got a problem with coolant pressurising the cooling system and filling up the overflow bottle. So from the start i bought a TD42T to replace a ZD30
and after completing the conversion i had this problem right from the start. I have searched the forum and have
done what most people have said and have done the following to try to eliminate the problem so far, raised the front end to
get rid of any air locks in the block whilst filling up the radiator, radiator pressure tested hot and cold, no problems there,
compression test on all cylinders and all good, had the thermostat changed out to a new one, new radiator cap,
changed it out for a 1.1 bar, the head checked for cracks (no cracks) and head machined, new head gasket, new head bolts, head torqued down properly.
Not sure if I've missed anything but what can anyone else think the problem might be or what to do next, any help would be greatly appreciated.

Cheers Owen

[4bye4]

Sounds like an air leak into the system. The water is filling the o/flow tank when hot, which is what its supposed to do, then not "sucking" the water as it cools. It will be sucking air from somewhere because it is easier than sucking water past the radiator cap seal.
Check hoses for tightness, gaskets and may even be the top radiator tank. If the hole is very small it will leak air in but not leak water out.

[Thor454]

4bye4 you just reminded of that, did check all hoses as i did read that someone was having that problem, so that's all good, i have a new radiator, hoses and gaskets as well.
Another thing i did after getting the head done was i dropped all the coolant and run straight water, mate of mine said it may be the coolant foaming up, so i got it up to
running temp with the radiator cap off and had it on ramps and noticed the bubbles in there still.

[mudnut]

Hello, Thor454, and welcome to the forum. The tiny bubbles could just be caused by the agitation of the water by the pump. Make sure the lip of the radiator filler neck is sealing properly and that the cap locking flanges underneath aren't worn. I had the very same problem with my RB30 engine and I had to use a fine wet'n'dry sand paper stretched over a flat block to sand the lip to make it seal properly..

Being an RB30 I had to take the fan belt off and run the engine to see if the bubbles were still there. (Only idle the engine for 5-6 minutes or you may damage it). As yours is a TD42 you may not have to do this.

[Thor454]

No worries mudnut i'll have a look at that but hopefully its not that being a brand new radiator, but you never know

[mudnut]

I have just changed out the head gasket, had the head machined and had the radiator reconditioned. The the new filler lip wasn't sealing so hopefully that is all it is on yours.

[Thor454]

Yeh I hope so mate

[Cuppa]

Hopefully as Mudnut suggests.

However:
I had the same problem in the motor in our bus. 4 cyl diesel. From that experience I reckon the following:

First things to do are to replace both the radiator cap & the small bore hose between the radiator & overflow bottle. Cheap & easy to do & may fix the problem.
If it doesn’t you have bigger problems.
Either a damaged head gasket, damaged or cracked head, damaged or cracked cylinder liner(s), or damage to the top of cylinder block.

In our case the overflowing overflow bottle was the *only* symptom. Motor ran as good as it ever had, & no bubbles observable in radiator.

The outcome was as shown in the pics

The head gasket had been blowing between every cylinder, & the result was that there was a deeply pitted area between each cylinder. The block was determined to be U/S & it was cheaper to fit another motor than to get the old one rebuilt with a new block. We had had a workshop in Geraldton work on it, & if they had done the right thing & removed the block & skimmed it’s top, it would have saved it, but they just fitted a new head gasket, knowing it wasn’t ever going to hold, & sent us on our way. It held for about 700kms & then the overflow bottle sympton returned. Syphoning the overflow bottle about every 300kms & returning it to the radiator worked for a while. By the time we had to call a recovery truck about 60kms west of Katherine, we were down to syphoning every 20kms. Not the best way to travel up te west coast & across to Katherine!

Again based on our experience - don’t leave it until you have no choice! If in the same situation again I think I’d be tempted to use one of these diagnostic kits

[mudnut]

B&&^$%%%$ds. It boils my blood when I hear of mechanics doing that to people, Cuppa. I am glad you weren't stranded a few hundred kilometres from anywhere.

That is sound advice regarding the test kit. Do you have a link for the kit, please?

[Thor454]

Cheers Cuppa, kinda thinking i might have a cracked liner then, i have done the combustion gas leak test with no signs of it leaking.

mudnut i brought one of the test kits from Repco if that helps, around a hundred bucks i think it was but you might be able to source one cheaper from somewhere else.