Air leak, bad carb, or something else?

[bustrucket]

Still happening sadly! Unfortunately this kept on getting pushed down the list by other stuff so I'm not much further forward, I decided to concentrate on getting the work done for the MOT first so I could actually test drive it, then once it passed it was the interior, work on the house in between and before I knew it it was winter and everything stopped again

Anyway, during all that I decided to try taking the radiator out and flushing it through, but once I got it off noticed that it wasn't in the best of nick and was the old thinner version, so I swapped it out with a new 44mm one. Again, didn't make much noticeable difference. Also swapped out the thermostat for an 80C, this actually did seem to help a bit, but temps were only slightly lower and still too high for comfort, maybe about 3/4 on the gauge instead of 7/8ths. This was during warm weather right enough, on a more recent run when the air temp was at least 10C lower the gauge was closer to 2/3rds. Fan still runs almost constantly once warmed up (cleaned up the thermoswitch when I swapped the rad).

Doesn't seem to be losing any coolant, level stays pretty constant. Got hold of another CO tester and "sniffed" the header tank a couple of times, didn't detect anything it shouldn't.

Finally got around to checking the plugs after a decent run, having said that the van has only managed about 300 miles on these so not sure if that's enough to show anything useful yet. Not managed to check the timing with vac off yet due to bad weather, if I remember right it would stall when disconnecting or pinching the vac hose.





Thanks

David

[T25Convert]

So to summarise:

New rad, new thermostat, well bled, no air bubbles.

Not running mega lean.

No combustion gas in the water.

Fan on pretty much all the time, scary gauge position.

I would be checking flow next - is the water getting around everywhere it should be. A dodgy water pump (for example impeller loose on shaft so it moves some water, but not enough) could give you this sort of issue, as could a blockage.

Have you had all the hoses off at strategic points and shoved a garden hose up to check water can move round like it should?

[937carrera]

I would tend to agree, reading back through the thread it is after all what I suggested in my intial comments, so I'm agreeing with myself as well. Sometimes it helps.

Rather than mess about with hosepipes, possibly inconclusively, I suggest the water pump is whipped off and inspected. Are they solid metal impellers, or the more modern plastic ones which tend to lose drive more easily.

[ajsimmo]

What cam did you use for the rebuild?

Sent from my ONEPLUS A3003 using Tapatalk

[T25Convert]

I would tend to agree, reading back through the thread it is after all what I suggested in my intial comments, so I'm agreeing with myself as well. Sometimes it helps.

Rather than mess about with hosepipes, possibly inconclusively, I suggest the water pump is whipped off and inspected. Are they solid metal impellers, or the more modern plastic ones which tend to lose drive more easily.

The only advantage of a hose pipe is that it gives you an indication of what the insides of the various bits might be hiding. If you get a flush return that looks like they van has been out enjoying 10 pints and a vindaloo then its probably sub-optimal conditions for flow. If however you get a strong flow of what looks like unicorn tears then its probably okay....

Agree, it won't tell you if the water pump is not doing its funky thing, only way to do that is to have it off. If its not new though, its probably worth just replacing it as they are not that expensive.

[bustrucket]

Sorry about the delay in replying, finally managed to get another look at this at the weekend there.

Stripped the pump, couldn't feel any play in the bearing, impeller is metal and looks to be in good condition although it's not a brand new pump. Thermostat housing isn't in the best of shape but still solid enough I think. I don't have easy access to a hose unfortunately but whenever the hoses are removed for replacing the rad or checking the pump etc the coolant is nice and clean, I don't think I saw any noticeable debris.

Some of the metal pipework isn't in the best of nick, I'm not sure what they're called but the upper pipe between pump and RHS head is a bit crusty inside with rust, but not enough to impede flow. No visible sign of leaks though. Top pipe across the engine about the same.

Do you think an electric "booster" pump be worth considering? Something like this: https://www.merlinmotorsport.co.uk/p/da ... -8005-ewp1" onclick="window.open(this.href);return false; ?

[bustrucket]

What cam did you use for the rebuild?

Sent from my ONEPLUS A3003 using Tapatalk

I was lucky enough to get a genuine DG NOS from (I think) VW Heritage before they went out of stock. Had to swap the gear, tried rivets but ended up using M7 bolts.

[937carrera]

OK, so metal impeller, that's good, I assume it is firmly affixed to the shaft and drive flange.

Don't waste time or money on the motorsport stuff. A T25 is not a stressed engine, no need to uprate any component, just make sure the standard stuff is working right.

I don't know if it's possible on a T25, on some cars it's possible to fit the thermostat the wrong way round. I would check that it is fitted the correct way and that the thermostat is working correctly. Either that or just bung another one in, you have a choice of an 80 or 87 degree one.

You can always get rid of some crud, but what you have shown doesn't look too bad at all. Perhaps also double check that all the hoses are connected in the right way, including the heater valve.

[bustrucket]

Can't detect any wobble in the impeller by hand, it all seems solid. Thermostat is fitted with the spring side facing up, and after taking the housing apart it looks like it won't fit any other way. It's brand new from Brickwerks so highly unlikely to be stuck, but I'll check it in hot water next chance i get.

When you mention the heater valve hoses, do you mean the valve at the front for the heating control?

I was considering running it without a thermostat (just as a test without that "restricting" the flow) but not sure if that would be of any value since it would leave the bypass route open all the time, possibly affecting the pumps ability to flow coolant to/from the rad?

Thanks

David

[937carrera]

There are many people who remove thermostats in an attempt to improve cooling, not understanding that depending on cooling system design that could actually impede the flow of water.... so don't bother.

The heater valve hoses I am referring to those are the ones that allow hot coolant to flow over the heater matrix at the front of the van, accessed by removing the spare wheel