Cooling System Query

[LittleNik]

Hi. Apologies in advance for my ignorance but we're still quite new to this! Our 1986 automatic 2.1 T25 has recently had a refurbished gearbox fitted. All is well except that the gearstick selector is now slightly off (it looks as though it's sitting between the N and D when it's in drive and just above the R in reverse). Consequently, when driving home from the garage, my husband stopped for fuel then set off again. He had to pull over when steam was coming out of the engine, the water from the tank was on the hot pipes. He now knows this is because he drove about 2 miles in 2nd gear (2) at 30-40mph on the flat thinking it was in D due to the gearstick misalignment. The 'death buzzer' for oil went off. On checking, the oil level was, and has remained, fine. He let the engine cool down then drove the final half mile home.

Today, we set off on a drive but only got about 3 miles down the road when the 'death buzzer' went off again. He had checked the oil and the coolant tank behind the reg plate before we left and both levels were fine. We pulled over and found the engine was steaming and red hot. He left it to cool then checked both the oil and coolant tank behind the reg plate and the levels were still fine.

A quick Google search at the roadside alerted him to the blue capped expansion pressure tank in the engine bay. He checked this and it was empty. He's now thinking that perhaps when he first drove home from the garage, the overheating had caused the fluid to empty from this tank (could that have caused the stream?) He topped it up with a bit of water and this got us home. However, as he pulled in outside our house more steam came from the rear of the van and the battery light came on, the van cut out. He couldn't restart but managed to do so half an hour later. He then topped up the blue capped expansion tank with about a litre of diluted coolant but this wasn't filling the tank, the level wasn't rising. He checked under the van and there were no leaks apparent.

Can anyone advise please? He's since read that he would need about 5-7 litres of coolant in this blue capped tank as it goes into the pipes to refill the radiator. Is this correct or could it be something else?
Thanks for any advice.

[ajsimmo]

If this happened on the way from the garage after having the refurbished gearbox fitted, it looks like it was down to the garage not filling and bleeding the cooling system properly. There's an oil cooler on the gearbox that has coolant flowing through it. They would have had to drain the coolant to remove the box, then refill and bleed when refitting the box.
With a properly functioning cooling system, driving a couple of miles in "2" wouldn't hurt the engine as it's only a 3 speed anyway, so you could drive at 30-35 in 2nd without overheating.
It prompts the question why the low coolant warning didn't flash, or temp gauge rise to top?
If the engine has now suffered an overheating event, it may have caused hidden internal damage due to low oil pressure (bearing damage), and heat expansion (stretched head studs).

Sent from my moto g(30) using Tapatalk

[icosahedron]

These vehicles are peculiar with the engine at the rear and the radiator up front. Both the radiator inlet and outlet are located at the bottom of the radiator, with the cooling pipes running underneath the vehicle to the engine. Coolant levels around the engine may appear normal, but if the coolant has been drained, an effort must be made to fill the radiator up front. While filling their cooling systems, some people rev their engine and others lift the rear or front of the vehicle; it's mind-boggling how the latter is supposed to work. I simply remove the bleed screw at the top of the radiator and fill it through a thin tube before starting the engine, all done on the level and at idle speed. It would be interesting to know how the garage went about it.

I hope that no damage was done.

[maxstu]

Adding to the two replies, l would expect the mechanic to simply clamp the pipes running to transmission oil cooler instead of draining the whole system.

And secondly, 40 mph in second gear is not going to cause overheating issues for a 2.1. Especially after just two miles; unless it is at idle in heavy traffic for a duration. Is the alternator belt sufficiently tight... or even there!?

If your mechanic did drain the whole system, it sounds as if she/he just poured some coolant in the expansion bottle (the one with the blue cap) without bothering to bleed the system properly for it to overheat in just two miles.

Get your mechanic on the phone and ask if the whole system was drained of coolant before replacing the differential.

[Alfredo]

Similar thing happened to us not long after we got it.
Took it to our usual garage, who we no longer use after a series of fails on their part with our van, to get a cracking hose replaced.
It overheated on the 3 mile journey home because they hadn't bled it afterwards.

Happy ending though because we found and now use for all our cars a village garage with good old fashioned know how and standards.

[Simon Baxter]

https://brickwerks.co.uk/blog/vw-t3-t25 ... -bleeding/

Also, the buzzer is oil pressure related and nothing to do with coolant temperature.

Sounds like you may have other things going on here.

https://brickwerks.co.uk/blog/vw-t3-oil ... -switches/

 

[ajsimmo]

https://brickwerks.co.uk/blog/vw-t3-t25 ... -bleeding/

Also, the buzzer is oil pressure related and nothing to do with coolant temperature.

Sounds like you may have other things going on here.

https://brickwerks.co.uk/blog/vw-t3-oil ... -switches/

 

Well, yes and no - an engine overheating due to lack of coolant flow will lose oil pressure due to excessively hot oil being much "thinner", therefore the buzzer is on as a result of high engine temperature.

Sent from my moto g(30) using Tapatalk

[Simon Baxter]

https://brickwerks.co.uk/blog/vw-t3-t25 ... -bleeding/

Also, the buzzer is oil pressure related and nothing to do with coolant temperature.

Sounds like you may have other things going on here.

https://brickwerks.co.uk/blog/vw-t3-oil ... -switches/

Well, yes and no - an engine overheating due to lack of coolant flow will lose oil pressure due to excessively hot oil being much "thinner", therefore the buzzer is on as a result of high engine temperature.

Sent from my moto g(30) using Tapatalk

It'd have to be super hot, the cutting out is concerning!
Doesn't sound like a very nice situation at all!


 

[LittleNik]

Thanks for all the replies. Spoke to the mechanic who had worked on the van and he confirmed he'd done all the draining and refilling mentioned here. Said we need to refill using about 7 litres of coolant but first to refill with water only to see if it's leaking anywhere. We couldn't see any obvious leaks but there are so many pipes so it's possible there may be a cracked piece of tubing somewhere.

We've decided to take it to a nearby mechanic for this, who has said he'll check it for us then refill/repair as necessary and do a full service. Just got to wait for him to get back from hols. In the meantime we have a motor electrician with knowledge of VW's coming to check the buzzer and dials for us. Concerned they're not working properly since the temp gauge also didn't go up during all this palaver.

Really hoping it's not something serious having just forked out 2.5 thousand for the reconditioned gearbox etc.

[Simon Baxter]

Thanks for all the replies. Spoke to the mechanic who had worked on the van and he confirmed he'd done all the draining and refilling mentioned here. Said we need to refill using about 7 litres of coolant but first to refill with water only to see if it's leaking anywhere. We couldn't see any obvious leaks but there are so many pipes so it's possible there may be a cracked piece of tubing somewhere.

We've decided to take it to a nearby mechanic for this, who has said he'll check it for us then refill/repair as necessary and do a full service. Just got to wait for him to get back from hols. In the meantime we have a motor electrician with knowledge of VW's coming to check the buzzer and dials for us. Concerned they're not working properly since the temp gauge also didn't go up during all this palaver.

Really hoping it's not something serious having just forked out 2.5 thousand for the reconditioned gearbox etc.

Temp gauge may not go up if it's simply low on coolant.
The light works 2 ways.

1. the coolant is low.
2. the temp gauge got too high


 

[maxstu]

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