Volvo Penta MD7a Water cooling system

[adriannor]

Originally Posted by MicHughV

I had that same engine....those fittings are a royal pain in the arse.....I had the same problem...could not get them to fit right and they leaked...

what I did was to make two cuts in the copper tubing about 4" or so away from that fitting....and with about a 3" gap to the next cut....then I spliced in a rubber hose to each end of the copper pipe...and clamped it on with a hose clamp...

this way I could fit that copper tail and rubber fitting perfectly into the hole where it needed to go...and let the rubber hose give me enuff flex to continue the to the next run of copper tubing....

never had a problem after that...

Thanks for the advice. How did you make the copper ends kept in place without the pressure on both sides of the metal tube ?

[JD-MDR]

Originally Posted by JD-MDR

The brackets 69 A&B hold it to the water pump and that's all I have. I had problems getting a seal. I pulled the pipe off and bent it a little so it would have some pressure to hold it in place. It's been holding up pretty good . There iwas a little sign of water stain but no visible leak and its a lot better than it was. I think it sealed itself . I painted everything about 100 hrs ago and the staining is pretty much stopped.

FWIW Mine is holding up good. No sign of leaking. It' been 10 months and 2-300 hours

[eurog]

Reading the initial post was like a memoir of my recent rebuild. And continuing with my woes was this copper coolant pipe and the fittings.
I will try with more rubber washers of varying sizes before splicing in a flexible end for the pump side as I am getting leaks on all 3 fittings. It seems trying to fit all 3 equally straight is too difficult. It may also be that I have cleaned up the manifold so much that the ports are larger??.

I do have a question though about the thermostat housing: Should it not have a gasket? It's metal on metal. I do have a small rubber o-ring for one of the ports and of course a new gasket for the thermostat but it still leaks like a sieve.
Even a gasket is not originally here, I think I will make one for it.

[hpeer]

For thermostats yiu can use some permatex.

[JD-MDR]

If I remember right there is a ring /gasket around the thermostat and an o-ring on the small port. Thats all. Mine seals fine. I had problems with the tubing but I got it all working good now.

[bplan]

Pandour:
I have just recently done exactly as you describe on my Volvo Penta MD7B as it was not cooling sufficiently also.
I cleaned out a lot of what appeared to be hard carbon build-up in the exhaust manifold. Many of the passageways were partly or mostly blocked. After reassembly the engine ran well and at a good temperature with adequate exhaust water flow. My problem is that after running the engine a few times and leaving the boat sit for a few weeks I find water in my crankcase oil. The engine will not start. Has anyone run across this problem or why would water be in the engine crankcase? Blown head gasket or where else to look?
Thank you in advance.
Brad

[hpeer]

I am NO expert.

My GUESS is that there are 2 possibilities.
1-Head gasket
2-A water passageway in the block rusted through.

No clue how to easily suss that out easily.

Removing the head is fairly easy, easy being relative. You can do it in the boat. Of course you need to source a new gasket of some alternative. If lucky you will see where it failed. If it looks intact the problem may be the block.

Do you have a shop manual?

If not PM me and I will try to send you one for an MD7A.

[hpeer]

AND…let me add…
Ince upon a time I pulled my MD7A and let it sit outside the boat all winter under a tarp. I reinstalled the motor and left on a 2,000 mile trip, much motoring. Day 1 I had milky oil. But I was no where bear a marina. So I kept running it for 2 more days to get to a marina and here I could investigate. In the meantime the water went away. I changed the oil and it never came back.

I figure it was from condensation. And the heat of the oil eventually evaporated it out.

Dumb luck but it turned out a zero issue issue.

Here’s hoping your problem is a easy as that.

[bplan]

hpeer: Thank you very much for your help. These options are what I was thinking as well so I feel a bit more confident in digging into it. I sourced a MD7A/B manual on line so I believe I have enough info to begin the process of removing the head and finding the problem. Also I have sourced parts for this engine from Marinepartsexpress.com and they have been very helpful both with advice and schematics, parts breakdowns online, etc. There may be some condensation getting in the oil (I think you were definitely lucky that the problem went away as it did) but I don't think I will be so lucky. The amount of volume change in the crankcase tells me that a substantial amount of water came in. Since the engine won't start now I suspect poor compression and very likely the head gasket.
Thanks again for the help and I enjoy reading the comments from other Volvo Penta owners on their repairs and experiences.
Brad

[Don C L]

In case you missed it, there may be info here to help:
https://www.cruisersforum.com/forums...o+engines.html

[bplan]

Thank you very much Don C L. I will check it out.
Brad

[Mongo_at_sea]

Originally Posted by Scubaseas

The pipe uses a square cut o-ring. The pipe or tubing must be perpendicular to the surface or straight in for it to work. Bend the tube if you have to being careful not to deform the end (put a snug fitting socket in it or bend it about 2" away from the end with a flat bar). You can get the o-ring from any Volvo car dealer or most car parts stores. At Volvo the sealing ring is listed in the climate control section for any 440, 540, 122, 144, P1800, 240, 260, 740, 940 series cars. A generic part is available as a "water pump sealing kit" for these same series cars. Volvo made it this way for about 40 years. O-ring gets installed with a bit of liquid soap or rubber friendly grease.

Or you could tap the hole for a 3/8 NPT pipe to hose nipple fitting.

Has anyone tried tapping the pump, cooling manifold and thermostat housing per above. Seems like a good idea to put in hose nipple fittings with flex pipe between. Two years ago I cut the pipe and placed flexible silicone high temp hose over the joints, but over two years saltwater crystals formed at the ends of the cut metal and blocked the line, and of course any time you touch the system it leaks until you play with it for a while.

[Scubaseas]

Originally Posted by Mongo_at_sea

Has anyone tried tapping the pump, cooling manifold and thermostat housing per above. Seems like a good idea to put in hose nipple fittings with flex pipe between. Two years ago I cut the pipe and placed flexible silicone high temp hose over the joints, but over two years saltwater crystals formed at the ends of the cut metal and blocked the line, and of course any time you touch the system it leaks until you play with it for a while.

You can but be mindfull the thermostat housing is thin cast and you night have to trim the nipple to fit. An alternative which would work fine is to machine a nipple to press fit into the hole. Same size, heat cover or manifold and freeze the nipper. Use some red loctite and Bob's your uncle.