Head Gasket?
Badger_McLetcher - 9/6/18 at 05:17 PM
'Afternoon all, hoping to pick some of your brains to confirmdeny a sinking feeling I have... I started up my project again today for the first
time in a while (been doing bodywork and didn't want it eating dust), and for the first time since I've re-jigged the coolant. It's an
AJ30 V6 out of a Jag.
The car has always done this thing where it pumps coolant out of the header tank, at first I thought I had it set up wrong (thus the rejig of the
system), however now I'm wondering whether it's the head gasket let go. The coolant level starts to rise as soon as the engine is turned on
and falls a second or two after it's switched off - it's not directly temperature related. On top of that there's a little bit of white
gunk on the inside of the filler cap, and a fair amount of fumes out of the engine breather...
On the flip side there's no white smoke, no coolant loss when it's not running etc.
I've also got a leaky hose, I don't think the thermostat is opening (the bottom hose is barely warm at all) and the tacho isn't
reading at all, so all in all a bit of a bad day tbh 
Any opinions welcome.
[Edited on 9/6/18 by Badger_McLetcher]
big_wasa - 9/6/18 at 05:53 PM
A “tiny” bit of mayo wouldn’t worry me on a project engine that has only run for a few seconds here and there. If it’s had a good run at this time of
year that would be different.
Got any diagrams / better photos on how you have plumbed it ?
Badger_McLetcher - 9/6/18 at 06:19 PM
I wouldn't say it was tiny, but it wasn't a huge amount either. More like a thin covering.
This is the original system:
Where:
1 — Water pump
2 — Water control valve
3 — Engine bank (right-hand)
4 — Heater
5 — Manual bleed tube (left-hand drive only)
6 — Expansion tank
7 — Engine bank (right-hand)
8 — Engine oil cooler
9 — Bottom hose
10 — Thermostat
11 — Radiator
12 — Top hose
This is how I've got it set up at the moment:
big_wasa - 9/6/18 at 06:34 PM
I am very new to the aj/Duratec 30 but how you have it plumbed doesn’t jump out as what I would expect.
I will go stick my head under the bonnet 
Badger_McLetcher - 9/6/18 at 06:39 PM
Part of that's due to my space issues, part is due to deliberately trying a different arrangement (as I said this happened before!).
The main coolant loop is the same, except without the oil cooler. The heater valve is bypass type, so it maintains a flow even when closed, and the
header itself is from a Clio.
When it fills up it does so from the bottom, so water is getting displaced from the bottom of the rad... maybe with the thermostat closed
there's too much pressure there?
[Edited on 9/6/18 by Badger_McLetcher]
wylliezx9r - 9/6/18 at 06:56 PM
I would start by drilling a couple of holes in the stat to get some flow going. IMO you will never truly bleed the engine untill the stat is open.
big_wasa - 9/6/18 at 06:59 PM
Yep I will be binning the modine oil warmer and the heater.
I am not used to these in line thermostats.
02GF74 - 9/6/18 at 07:07 PM
When you Rev the engine, does the level in header tank rise and fall in sync?
Spend 8 quid on a bottle of tester to rule out hg failure.
[Edited on 9/6/18 by 02GF74]
Badger_McLetcher - 9/6/18 at 07:48 PM
Thanks for all the replies guys! A couple of good things to try there, gives me a bit of hope
quote:
Originally posted by 02GF74
When you Rev the engine, does the level in header tank rise and fall in sync?
Spend 8 quid on a bottle of tester to rule out hg failure.
[Edited on 9/6/18 by 02GF74]
It doesn't fall again, but it certainly fills up more rapidly with a higher RPM. Good call on the HG tester, though I'll probably need to
retrieve coolant from the hot part of the system as I don't reckon the cooler stuff (e.g. in the header) has been cycled at all.
big_wasa - 9/6/18 at 08:22 PM
Looking over mine.
Have you got a bleed from the top of the rad to the top of the header tank ?
Badger_McLetcher - 9/6/18 at 08:30 PM
Kind of - I've got one going from the top hose (which goes into the top of the rad) to the header tank. It's basically tapped off the
pressure side of the heater pipe, just before the valve (which as I said is a bypass type, so should keep flow going even when it's closed).
big_wasa - 9/6/18 at 08:40 PM
Mine has two, one in the top of the rad and one in the top hose but close to the block.
So looking over it now, other than where your tapping in or taking off for packaging reasons it looks pretty close to my st220
Badger_McLetcher - 9/6/18 at 09:02 PM
Aye, I was trying to keep it relatively close to stock... doesn't seem to have helped too much though!
big_wasa - 10/6/18 at 07:58 AM
I still wouldn’t expect it to move that amount of coolant when cold. Still sounds like an air lock.
40inches - 10/6/18 at 10:15 AM
Are you using the Jag stat? If so bin it! It opens at 105degrees
I used an early 3 series BMW, works much better.
I haven't got a heater so my cooling system is a little different.
I tried to follow the Jag system, but the outlet from the pump (to heater?) goes to the bottom of the header tank, I have a small hose going from the
coolant outlet in the heads valley to the top of the header tank. I will put some photos up later.
Badger_McLetcher - 10/6/18 at 12:36 PM
quote:
Originally posted by 40inches
Are you using the Jag stat? If so bin it! It opens at 105degrees I used an early 3 series BMW, works much better.
I haven't got a heater so my cooling system is a little different.
I tried to follow the Jag system, but the outlet from the pump (to heater?) goes to the bottom of the header tank, I have a small hose going from the
coolant outlet in the heads valley to the top of the header tank. I will put some photos up later.
Aye, I'm using the Jag one at the moment. I'm guessing you've got an E30 stat as a replacement? Wouldn't mind swapping it out for
something a bit more reasonable
The heater isn't getting hot at the moment, which makes me think there may be an airlock in there somewhere... however it may also be a pinched
hose, as clearance under the scuttle is very tight. Need to get the dash off to check.
I've gone over the system to try to make sure there's no airlock in the main circuit, I'm relatively certain that there isn't. I
also clamped the bottom feed of the header tank partially closed to restrict flow, just in case that was part of the issue - no change, as soon as I
started the car the coolant started rising. Siphoned some back out, restarted and it kept filling up. When the engine is stopped it falls slowly back
down.
Unfortunately from reading S-type forums (where a couple of people have had the same symptoms) it's again pushing me towards this being a HGF 
40inches - 12/6/18 at 09:01 AM
I think E30 is correct?
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I think I would get the engine running up to temperature before thinking about HGF.
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Badger_McLetcher - 13/6/18 at 08:11 PM
quote:
Originally posted by 40inches
I think E30 is correct?
I think I would get the engine running up to temperature before thinking about HGF.
Awesome, thanks for the reply. I'll probably look at getting one of those and swapping the Jag one out, unless it all starts miraculously
working!
It looks like our primary coolant loops are set up in roughly the same way - a lot of mine is determined by the fact my rad's got the ports on
the sides. Unfortunately mine's not that easy to play around with as in my wisdom I remade most of it out of ally tubing to reduce the number of
joints! Figured it would help lose a bit of heat as a Brucey Bonus.
I had actually got it up to temp the first time I ran it before I noticed the coolant overflowing. I was slightly distracted by the smoke pouring off
the headers as the VHT paint cured!
I've got this Friday off, so will have another play around with it - I'm going to pressure test the system (by bodging in a car tyre pump
to do it), use the head gasket checking kit and reroute the pipes for the heater which have become pinched. I've even got a new cap for the
header tank just in case it's that...
Push comes to shove I'm playing with the idea of raising the compression ratio a bit if the heads have to be skimmed 
If it's all got to
come apart I'll also likely add some strategically placed bleedfill points into the hard lines when I swap the thermostat.
froggy - 14/6/18 at 11:46 AM
I’ve only done one head gasket failure on these engines and was after a total loss of water.
Mr Whippy - 14/6/18 at 11:51 AM
best way to check is to do a compression test, that will show clearly if you have a head gasket leaking
Badger_McLetcher - 16/6/18 at 10:57 PM
Thanks for all the comments and advice guys, time for an update...
IT'S FIXED
I stripped down the system and rebuilt it with a couple of tweaks yesterday and today, including taking the top hose from the engine outlet rather
than a bit further downstream (as 40Inches system - thanks again for the pics!) and the new tank cap (the old one was actually knackered).
Using a schrader valve bonded into a bit of tube that I teed into the top hose I then pressure tested it - after fixing a couple of leaks it looked
ok. After that I filled the system up and used the valve to pressurise the system, I assume that forced the water around the system and helped get rid
of the airlocks as I had to top it up a couple of times doing that.
After all that I ran the engine and she got up to temperature absolutely fine, thermostat seemed to open about 90 degrees so not too bad at all. No
leaks, no loss of coolant - I'm very happy!
[Edited on 17/6/18 by Badger_McLetcher]
