Leyland P76 Owners 2004

Technical Question and Answers

Detecting Manifold leaks

Question

From: "MICK & MARYSE CLARKE"
Date: Sat, 20 Mar 2004
Adrian I have a question for the email group........the P76 4.4 engine over its life seems to have a tendency to blow inlet manifold gaskets causing associated problems.
Can anyone advise me of an appropriate test to find out if your inlet manifold does have a leak and the best way to rectify it so it doesnt happen again.
In the past someone advised me to pour some brake fuild along the manifold join to the block and see if the exhaust blew white smoke (never tried it).
I have also heard the reasons for this tendency to blow gaskets is related to the flexible nature of the aluminium blocks...that when the engines were being built they were supported from one end and effectively bent slightly under their own weight, leading to poor sealing characteristics along the length of the cylinder head/inlet manifold join.
Is this true?
I would be grateful if any opinions/knowledge or expertise on this topic to be shared with the whole group, lets nail this one down.
Cheers
Mick Clarke Vic.

Replys

From: " Robert C Wild" USA
Date: Mon, 22 Mar 2004
Mick and Maryse,
At last I find a subject I'm familiar with and can join in with a response.
You're correct in identifying the best way to confirm a manifold leak.
Any oil applied to the join will get sucked in as you say. You'll see it get sucked-in without examining the exhaust colour. The idle will also have deteriorated as the leak will put air into specific ports and cause a miss at idle. It was this poor idle condition which on several occasions led me to this problem.
This problem was originally associated with early gaskets which were of laminated manufacture, sheet metal and some fibre material I recall. By the end of 74 an aluminium, embossed product was introduced which never gave me any more trouble after it was fitted, as it accommodated machined surface mismatch.
What was the route cause of the leak? I think the speculation that it is cylinder block casting distortion is not the answer. It was probably about machining quality and accuracy, of both, or either, the heads or manifold, or block. Most likely an accumulated condition thru all three.
Best wishes,
Bob Wild
From: "Stuart"
Date: Mon, 22 Mar 2004
Hi All
Brake fluid is an excellent test for leaks in the inlet manifold.
Repairing it is also easy.
Make sure the surfaces are very clean and true (machine them if necessary. Note: if you take some off these two you will also need to face the heads to match.)
Spray the new gasket faces liberally with spray Hylomar (obtained from Repco, Brush on one is cheaper but does not always work!)
Then reassemble as normal.
Unless you seriously overheat it you won't have it leak again.
Regards,
Stuart
From: "Nick"
Date: Mon, 22 Mar 2004 12:26:57 +1100
Hi,
I thought I might add my 2 cents worth.
In my experience with p76s I have found 2 ways of fixing the problem.
If the heads have been machined (surfaced) misalignment will occurr if the holes in the inlet manifold are not drilled out to half inch (bolt head size) which will align the manifold correctly.
I have done this with std 2 bbl manifold and willpower ones of which the latter seem to be slightly out from new. because of the offset to 90 degrees angle of the way the bolts attatch to the head they are easy to cross thread the bolts or if one bolt has snapped off when pulling apart (and the head as been helicoiled).
A guy I used to work with as kid never used any sealant on the manifold faces and at one time sent 7 back to ACL QLD as the "CAFF material" was not glued correctly and slipped down over the ports causing the car to run rough and misfire like a blown head gasket.
I have always used permatex ultra red or blue on the manifold faces and torqued the bolts down in 3 stages and in the sequence as per the workshop manuals,and not rand the engine untill the sealant was dry.
After a suggestion from Andrew kloot from whom I had bought a home made 4 bbl manifold from (based on a std one),he used this manifold with all the gasket (black) material peeled off so the tin valley gasket was left, and then used black siliastic which worked in the car for about 70,000klms.
A Rover 3.5 to 4.6 uses this type of valley gasket design and does not seem to suffer this type of problems at all.
One sign of a blown or leaking gasket is putting the car under load say in 3rd or top gear and "lugging " the motor and if the blown gasket is in its early stages it seems to make a pinging noise even if the timing is set to STD (I always run my engines at 6 to 8 advanced).
I hope this helps.
Cheers,
Nick Tassie
From: "Andrew"
Date: Mon, 22 Mar 2004
Hi,
The best way to cure this problem is to remove all paper from the inlet manifold gasket with a wire brush in a power drill or bench grinder.
Then go down to your local loctite specialist and buy a tube of loctite 515 or 510 and apply to all cleaned surfaces and tighten manifold down as per procedure in the workshop manual.
Allow 24 hours to set on the meeting surfaces before starting and hey presto your problem should be permanetley cured
Regards,
Andrew
From: Hal
Date: Mon, 22 Mar 2004 16:16:39 +1100
To All:
I use Loctite 515 on all my competition engine inlet manifold gaskets and have never had a falure.
I am sure others will also had success in other ways,
Hal
From: "Fleur & David WATERS"
Date: Tue, 23 Mar 2004
Hello,
dont forget that most leak under the tray into the oil area.
The only test is to remove the manifold.
You could remove the carby and the intake valve rockers and pressurise the manifold but you have to be chasing silly leaks.
Hal might know but i thought the pressed steel gasket was the original and the gasket with the paper added was to FIX the leaks.
Engine vibrate.things move.alloy has no memory and distorts easily.
515 [new number now I think] is a surface jointing paste that stays soft.
Dont ever use silicon.
But more important is that gaskets are not meant to last forever.
Gaskets are not covered by new/used car warranties as they are service items, IE regularly changed.
I believe that Ford think on the Falcon should only last 80 000km.
David L WATERS
Fleur L WATERS
NSW AUSTRALIA
From: "Nigel Bray"
Date: Tue, 23 Mar 2004
I have used the brake fluid method, can be difficult to watch what you are doing and the exhaust at the same time. A 1" paint brush dipped in petrol and brushed slowly around the manifold will indicate a leak by an increase in idle speed as you brush over the leaky bit, works OK if you are on your'e own. Obviously you can only test the top part of the flange with these methods but any leaks I have had have always been on the top.
Fix seems to be, remove manifold and gasket, clean and replace using quality gasket goo, blue oil resistant silastic or similar. I have even removed the gasket material from the sheet metal and just used it and silastic with good results.
regards,
Nigel
Last updated
Jan, 2005
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