[P38] Exhaust gases in coolant

blue_cheese · Friday at 09:59

MrGorsky said:
I'd say do a compression test. If that's good, then just change the HG. It's mostly easy to do. If you've got no or low compression on multiple cylinders you're probably looking at a rebuild anyway and you can decide what to do then.

Even just taking the heads off will tell you if it IS the HG or not. If it is, you know what to do, if you get it all apart and the old HG looks perfect, then you know you're dealing with something worse....and you can decide what to do from there.

Getting an otherwise usable engine rebuilt is not really worth it if all you need to do is change a head gasket to get it running again.

Apologies if this is a stupid question, but wouldn't the compression test fail regardless of if it was a HG issue or a block issue?

kermit_rr · Friday at 10:00

I had good compression on mine with a cracked block. Plus they tend to seal up when the engine is cold

Mark Piercy · Friday at 10:14

blue_cheese said:
Apologies if this is a stupid question, but wouldn't the compression test fail regardless of if it was a HG issue or a block issue?

It's a good question, it depends on the knowledge of what your dealing with and the symptoms.
Any loss of compression and it's most likely heads off time.
Your choice how you choose to approach it.

MrGorsky · Friday at 11:00

What I should have said was if you have low compression in none, or maybe one or two cylinders and the rest are good, then it's worth digging a little deeper. If you've got low compression on the whole engine then you know from the off you're looking at more work whatever happens.

Probably not worth wasting your time thinking about changing a HG on an engine with all low compression.

When mine developed starting problems a compression test showed low compression accross all cylinders so I knew I was looking at a new, or replacement engine no matter what!

A compression test is quick and easy (and cheap) to do.

blue_cheese · Friday at 11:04

pwood999 said:
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

Just been looking at this catalogue, am I right in thinking that this is what I need:
AZ510A No front row-20 per engine

Want to confirm as a lot of the sets I've seen have only included 10 studs

pwood999 · Friday at 11:07

Yes 10 studs per head, so 20 total. Do shop around just in case. Realsteel were cheapest genuine Arp when I bought mine a few years back, but you never know !

blue_cheese · Friday at 11:23

Thanks, they look to be the cheapest at the moment.

I've called nine (9!) garages so far, none of them do compression testing!
I'd rather not buy my own kit for a one time use.

The search continues

kermit_rr · Friday at 11:30

blue_cheese said:
Thanks, they look to be the cheapest at the moment.

I've called nine (9!) garages so far, none of them do compression testing!
I'd rather not buy my own kit for a one time use.

The search continues

a compression tester is cheap enough

Datatek · Friday at 11:34

kermit_rr said:
a compression tester is cheap enough

Yes very cheap, less than the cost of a garage doing a compression test.

marjon · Friday at 12:17

blue_cheese said:
Thanks, they look to be the cheapest at the moment.

I've called nine (9!) garages so far, none of them do compression testing!
I'd rather not buy my own kit for a one time use.

The search continues

For the cost of a kit and DIY it would work out cheaper than labour cost at a garage. Edit I see thats already be said so must be true

.

The kit could always be sold after if you didnt want to keep it and probably recoup most of the cost.

J

pwood999 · Friday at 14:09

£15 on Amazon.

aj1954 · Friday at 14:15

kermit_rr said:
a compression tester is cheap enough

I got a Laser one, £20.

blue_cheese · Friday at 14:19

I've just been to Halfords and picked one up.
I'll have a crack at it in the morning - are any of the plugs particularly tricky to get out on the Thor engines?

MrGorsky · Friday at 14:39

Back one on the LHS as you look at the engine. It's number 8 I think is a bit of a bugger. But you will manage.

Start them off only with your fingers when putting them back or you risk cross threading them.... and you've got enough jobs already!

Get them all out, and take the reading with wide open throttle and also with and without a drop of oil down the bores. This gives you a reading dry and wet. A big difference between the two can point to worn rings.

kermit_rr · Friday at 14:42

MrGorsky said:
Back on on the LHS as you look at the engine. It's number 8 I think is a bit of a bugger. But you will manage.

Start them off only with your fingers when putting them back or you risk cross threading them.

Wind it back on the the thread and you'll feel it click into place through your fingers

MrGorsky · Friday at 14:44

Also, this is what I found when I did mine....

P38A - Compression Test Results.

Morning Everybody. My misfire under load is still apparent, so I've bought new plugs and other bits to see if that helps. Whilst changing them I did a compression test and these are the results I got.... with my cheap eBay tester. 1=125 2=130 2=130 4=145 5=125 6=155 7=130 8=140 All...

www.landyzone.co.uk

blue_cheese · Friday at 15:18

MrGorsky said:
Back on on the LHS as you look at the engine. It's number 8 I think is a bit of a bugger. But you will manage.

Start them off only with your fingers when putting them back or you risk cross threading them.... and you've got enough jobs already!

Get them all out, and take the reading with wide open throttle and also with and without a drop of oil down the bores. This gives you a reading dry and wet. A big difference between the two can point to worn rings.

What's the purpose of keeping the throttle open? Apologies if a silly question.
I've removed fuse 39 (Fuel Pump) so stop the engine going while I'm running the test.

Just tried to remove the first plug - my ratchet wrench is comically oversized for this job so might have to take the exhaust heat shield off.

Datatek · Friday at 15:24

blue_cheese said:
What's the purpose of keeping the throttle open? Apologies if a silly question.
I've removed fuse 39 (Fuel Pump) so stop the engine going while I'm running the test.

Just tried to remove the first plug - my ratchet wrench is comically oversized for this job so might have to take the exhaust heat shield off.

Throttle open to let air in on the induction stroke to be compressed for the compression check.

pwood999 · Friday at 17:01

MrGorsky said:
Back one on the LHS as you look at the engine. It's number 8 I think is a bit of a bugger. But you will manage.

Start them off only with your fingers when putting them back or you risk cross threading them.... and you've got enough jobs already!

Get them all out, and take the reading with wide open throttle and also with and without a drop of oil down the bores. This gives you a reading dry and wet. A big difference between the two can point to worn rings.

Best to do it without & then with a drop.

kermit_rr · Friday at 17:27

And pull the fuel pump fuse so you don't get fuel everywhere

[P38] Exhaust gases in coolant

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