Water pump to block mounting bolts

[mangocrazy]

Bit of an odd one, this. I'm currently cleaning up the water pump that was briefly fitted to my Spider 2000 engine before its untimely demise and I could have sworn that the 4 bolts that hold the water pump body to the block were M8 size. But when I look more closely at the water pump body, all of the mounting holes are between 6.5 and 7.5mm. This leads me to think that the pump is held to the block by 4 x M6 bolts. Is this the case?

Thanks in advance.

[mangocrazy]

Answering my own question - the bolts are indeed M6. The parts book gives the following part numbers for the mounting bolts:

10902621 - Bolt, short (M6 x 25 according to Google) - 2 off
10903421 - Bolt, medium (M6 x 45 according to Google) - 1 off
10903621 - Bolt, long (M6 x 50 according to Google) - 1 off

[SanRemo78]

Mark does a stainless steel bolt kit for not many pennies!

[WestonE]

Remember the copper washers that go next to the pump body at the bolt head end typically with a steel backing washer. These copper washer need to be new because they deform to seal the hole.

Eric
PS I used stainless cap heads and stainless washers with spring washers. Either Copperslip at the block end or omit the spring washers and use the softest locktite.   

[mangocrazy]

I'm intending to use M6 stainless flange bolts and (as Eric suggests) a drop of the 'weak' Loctite. I might also add copper or aluminium crush washers in the cause of belt and braces. It's not a job I want to be repeating any time soon...

[Neil-yaj396]

The M6 bolts always seem somewhat small to me for this job. Not the usual Lancia over-engineering....

[mangocrazy]

The M6 bolts always seem somewhat small to me for this job. Not the usual Lancia over-engineering....

Yes, that was my thought as well. I guess that if you had the block on an engine stand you could enlarge the bolt holes to M8, as there's enough meat on the water pump body for the holes to be enlarged to 8mm +. But it's not something I'd think about doing in situ.

[Nigel]

Hi,
The only force acting on the pump body is from the v belt, and as it's
a rotational force, plus a bit of tension, it's not particularly high. Provided the bolts, threads,
mounting surfaces and the pulley bearing are all in good condition,
I don't see an issue.
Although the pump may well take larger bolts, the block is already compromised
by the threads, or some of them, entering the water jacket. Enlarging those
may well lead to unintended consequences!

[mangocrazy]

Hi,
The only force acting on the pump body is from the v belt, and as it's
a rotational force, plus a bit of tension, it's not particularly high. Provided the bolts, threads,
mounting surfaces and the pulley bearing are all in good condition,
I don't see an issue.
Although the pump may well take larger bolts, the block is already compromised
by the threads, or some of them, entering the water jacket. Enlarging those
may well lead to unintended consequences!

Yes, you're quite right. I'm sure Lancia sized the bolts adequately. They did use M8 studs on the water pump to back rail flange, so it was clearly a conscious decision to use M6 bolts on the pump to block connection.

Graham