Overheating when driven

[KatnDougal]

Thanks for that. I shall go and take it off them tomorrow. Yes it is a late '86 camper. There is some hot coolant getting to the radiator but I presume that is just fluke. I think their bypass of the heat exchanger just proves the van heating doesn't work! I don't suppose you have any good mechanic recommends in the North of Scotland between Inverness and Aberdeen do you?

[kevtherev]

What's this "heat exchanger" you speak of?

[kevtherev]

Print the cooling system schematic off and show it to them
see what they say

[KatnDougal]

I shall take it with me. The heat exchanger is in the van behimd the dash to provide heat internally. The garage says it is linked to the radiator in terms of coolant and creating excess pressure in the system if coolant cant flow through it freely.

[kevtherev]

Ah the heater matrix
no it's not linked to the radiator, and you control it by restricting the flow... and turning the flow off in the summer, by the heat controller

I've never heard anything like the tosh these fellas are saying..

The garage says it is linked to the radiator in terms of coolant and creating excess pressure in the system if coolant cant flow through it freely.

[ghost123uk]

Firstly apologies for not posting any information on your issue, but Kev seems to have it in the bag, esp with the v nice diagram, but when you say =

I am just a bit concerned that the piping for the main system still isn't right and I have a bad feeling that I am starting to know more than my mechanic...

This is not unusual, esp once you start to understand these vans (often via here !)

Your average garage mechanic is often in the dark (and will often talk bull pooh) when looking at a T25.
It certainly sounds like your mechanic falls into this category.
T25 experienced mechanics are quite rare and therefore valuable and should be sought out and then looked after

Someone will be along soon to recommend a T25 mechanic near you

[KatnDougal]

Update:
Since my last post a lot has happened - the main thing is I removed my van from the garage as they were doing no investigation just replacing parts...

I tested the dalek and realised I could suck and blow through it so replaced it with one from brickwerks.
Now pressurised, the system revealed a split in the coolant flange so replaced that and corresponding gasket (that had previously been glued together and also revealed the old flange was blocked with gunk).
I re-bled the system (I think I did it correctly to get all the air out) - and hey presto the radiator got hot and the fan kicked in for the first time!
All excited that I may have solved the problem I took the van out for a short (half mile) spin. No overheating (getting more excited), water running low in header tank (getting less excited), still not overheating (ok, drive further), pipe from header tank to expansion tank gets blown off of dalek!
I stop, no water in top-up tank, apparently none in header tank either but when I then half turned dalek cap, water fills up header tank to full. WHY???

Next day I think this may be that the hose needed to be clamped onto the dalek so jubillee clip it together and try again. This time, all looks good, no overheating, water starts running low in header tank again and light starts flashing on dash but still no overheating, continue driving and then pop, water spurts out of a new split hose between engine and coolant distributor, still no water in header tank or top-up tank and radiator appears not to have even got hot this time!

Am I not bleeding the van correctly and so creating an air bubble that causes excess pressure? Also, should I have water in the top-up tank when engine is cold?

Any help appreciated...

[edoh]

for sure you should have water in the top up tank -
is there a min / max mark on it? My understanding -
top up tank should be between min and max - and what the dalek goes into - should be up to the top - always -
are you bleeding the system a la wiki instructions?

[KatnDougal]

I did wonder about that and thought it was just a marker for when the pressure built up and water came in from the header tank. I used a different method for bleeding but next I will try the WIKI way!

[Ian Hulley]

Your average garage mechanic is often in the dark (and will often talk bull pooh) when looking at a T25.
It certainly sounds like your mechanic falls into this category.

Our's did in Belgium .... " gearbox Pah ... where is ze gearbox ?" As the spare wheel landed on him

[dubuffet]

Your average garage mechanic is often in the dark (and will often talk bull pooh) when looking at a T25.
It certainly sounds like your mechanic falls into this category.

Our's did in Belgium .... " gearbox Pah ... where is ze gearbox ?" As the spare wheel landed on him

[ghost123uk]

Hi KatnDougal

A bit worrying as if the system is pressurising enough to do the things that have happened, the dalek cap should be venting excess pressure into the top up tank (behind the number plate flap - this tank has vents to the outside world at the top).

I had this once and it turned out to be 2 things.

Firstly the thin metal coolant pipe that runs around the lip of the engine bay (on post 85 models) has "T" pieces in it.
On mine, the "T" piece that fed cooling water to the L/H head was totally blocked with crud.
This caused the head to overheat so much that it boiled whatever water was in there causing a big build up of pressure.
The Dalek cap did not vent the pressure and mine kept bursting hoses etc.

Fixed it by draining, cleaning all the thin pipes of crud, which involved poking up the pipes with stiff wire etc to clear them and I replaced the cap.

A thread about this issue that happened to some one else (with pictures) is here =

https://club8090.co.uk/forum/viewtopic.p ... 4&start=30" onclick="window.open(this.href);return false;

Look for the picture near the bottom of page 3

Here is the pic =



Not saying this is your problem but worth a look.

Have you had anyone put the combustion gas sniffer tool on your vans coolant tank yet ?

Excess pressure can be caused by a blown head gasket

That thread above is worth a read, but don't panic (just yet) get a sniff test done to eliminate the head gasket.

Good luck

[KatnDougal]

Thanks for that. I was wondering if there is a chance of build up in that pipe as there has been some in others. I think I shall disconnect all the jubilee clips and poke a wire through as suggested. The garage finally did a sniff test before we brought it home and they said it was negative so hopefully (if they did this right) there is no problem witht he head gasket (at the moment). I shall certainly read the linked post you mention.

[ghost123uk]

In response to some curiosity re this I started a question here re excess pressure =
https://club8090.co.uk/forum/viewtopic.php?f=37&t=86556" onclick="window.open(this.href);return false;

[KatnDougal]

Ok, further update:

I checked the pipes and just the same as ghost, the t junction from the bleed pipe into the l/h engine was blocked, so unblocked it and water flowed through.
Bled the system 3 times using Wiki process. Then decided to go for a drive. I got a lot further (1.5 miles) and then boom, top-up tank split in half! Took it out and turns out some git had blocked the 3 holes at the top of it with super glue, so pressure built up and had nowhere else to go!
Replaced the top-up tank today, bled the system 1 last time and went out again. Got a lot further, no overheating, no water leakages anywhere, nothing bursting or blowing up. BUT, the temperature line was going up over the red light and sitting there and intermittently going higher, so pulled over and fan not on but radiator v hot, water in expansion tank gone down to half (at min point), top-up tank still at max level no change, wiggled wire to thermoswitch and fan came on for a short spell (a few seconds) and then went off again. Temp came down to sit at right side of light again. Set off again and this time went at about 40mph and temp went up to 3/4 and I couldn't hear the fan, coolant increased in top-up tank, expansion tank still on half.
Went home.
Questions:
At what level should expansion tank be when hot, should it go down to half and be half liquid/half air? And should it refill again when cold?
At what point should fan kick in under load? Could it be a wiring issue?

p.s. only when i release the pressure off the dalek cap (when cold) does the expansion tank fill up to the brim with water again...

p.p.s i have just noticed a drip coming from the large rubber seal around the right side of the engine block - is it the water jacket seal and will these cause me problems?