[P38] Exhaust gases in coolant

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B

blue_cheese

Member
Posts
17
Location
Port Talbot
Hi all,

Got a 1999 4.6 Thor.
Recently noticed that the coolant level has been dropping, idling has been a little rough, and sometimes harder to start.
Topped the coolant up but it's low again a week later.
The car hasn't overheated, and stays around middle on the temp gauge when driving.

I bought a DIY exhaust gas test (the type that connects to the coolant overflow tank - Amazon) and the liquid changed colour from blue to yellow, indicating the presence of exhaust gases in the cooling system.

My question is - does this almost certainly point to head gaskets / slipped liners? Or is there somewhere smaller I should start looking before I start pricing up the work?

Many thanks
 
I've only had the car recently, previous owner said it hadn't overheated, but take that with a pinch of salt. There's some copper dust around the coolant overflow cap, so I'm thinking maybe someone tried some leak sealer before.
It's petrol only. Is there a way to differentiate between HG and block issues without disassembling?
 
It can also be the front cover gasket weeping into the coolant around the water pump.

Definitely worth doing compression test on all 8 cylinders. Take all the spark plugs out first.

Also flush & refill the coolant with water, and test again after it's run for 10-20mins.

Put your town name in your forum profile.
 
Unfortunately there is no way to know who the culprit is without disassembling but don't bandage your head before breaking it, most likely it's just the gasket. You will have to disassemble the two heads if it is necessary to smooth and change the gasket. If you want to try to keep costs and work down, do a compression test to see which bank has the problem. If you have a wire cam for a smartphone, you can look through the spark plug hole, if you find a cleaner piston it's almost certainly the culprit. The coolant in the combustion chamber cleans carbon residues. Good work !
 
Plugs should look like the left one. If any are like the right plug, almost certainly head gasket.

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Thanks all for your advice. I've added my town - feel free to suggest any trustworthy LR mechanics nearby!
Sounds like my next best step is to do a compression test.

I've replaced a HG before but that was on a Rover K series engine - much simpler. I don't have the capability or tools for this job, so it will have to be a garage job.

I'm hoping it's just the gaskets, and a head skim + refit will do. Had one of these years ago which had a cracked cylinder wall, so praying it's not that again. Was a nightmare to find a garage that was willing to take on the job!
 
kermit_rr said:
only skim if the surfaces arent flat.
if you do need to skim then you MIGHT need rocker pedestal shims, tho its not guaranteed
Click to expand...
I always say it too, check flatness with a rectified ruler, if it is out of clearance you plane. All the workshops around here dismantle and plan without even checking :mad:
 
Thanks again for your advice. I don't have the tools or space to try and tackle this outside my house, so it looks like I'll have to search around for a garage that will take it on
 
Make sure the garage adheres to the LR specs. If you do need to have the heads skimmed, make sure they do both the block & inlet faces by the same amount. This will ensure the inlet manifold fit properly.

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Valley gasket needs to be done properly with some RTV in the 4 notches where the heads meet the block. Also I recommend some coolant sealer (Hermetite or similar) around the two coolant passages at either end of the heads.


1740414890374.png
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I've done a little more research in to DIYing it, and I've seen the debate about stretch bolts vs ARP bolts come up quite a lot. What's the general consensus on the matter here?
 
Datatek said:
HGF, cracked block or dropped liners, no way to tell with out taking it apart that I know of. Just prey it's HGF because the other options are serious money to fix.
Click to expand...
A liner problem is easy to diagnose, but hopefully that is not your problem as the condition is terminal.
If you have a slipping liner the engine will be quiet when cold but as it starts to warm a distinct metallic tap (at piston speed not valve gear, which is half that) will be clearly audible.
 
blue_cheese said:
I've done a little more research in to DIYing it, and I've seen the debate about stretch bolts vs ARP bolts come up quite a lot. What's the general consensus on the matter here?
Click to expand...
When I rebuilt one of mine, I found the prev owner had overtightened the stretch bolts & damaged the block threads. Got the block helicoiled, and used Arp Studs. Much easier to torque the heads properly. The only downside is the cost is several times the price of new stretch bolts.

To answer your question, my opinion is Arp Studs every time.

Realsteel in Cowley seems to be the best price I can find. Look on page-5 in this link. http://www.realsteel.co.uk/section1.pdf
 
Yeah when i got my P38 it had a blown HG. It was a very small compression leak into atmosphere though with no pitting on the block or head, so i was very lucky in that regard. Fitted ARP headstuds and new elring gaskets.
I fully agree with the ARP headstud route, they reusable, you can get way better clamping load on the HG so less risk of a blown HG in the future and way less risk to the threads in the block.
 
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