Volvo AQ131A overheating

[rteeng]

I have a Volvo AQ131A motor and the outdrive number stamped in it is 876981 I do not know if it is Volvo. I recently bought the boat from a friend. The boat sat for about a year without being used. It is on a 1986 Bayliner and believe everthing to be original.

I took it out tubing and the engine started overheating. I removed the thermostat and tested on the stove. It just starts to open at 185?.

I left the thermostat out and made another test run. I took things slow for awhile and the temperature stayed low (about 125?). I then opened it up and about the same time I made a sharp turn it overheated spraying on the distributer (yes I was stuck on the lake).

My next test was to put the outdrive in a tub of water and ran the engine for about 20 minutes at about 2000rpm and it did not overheat (again, thermostat removed). I removed the radiator cap and could see the coolant circulating. I could see water spraying out of the lower unit with the exhaust. I don't know how much should be coming out so I can't comment on if it seemed normal.

I have a raw water pump on the front of the engine but is there one in the lower unit also? What should I test next?

 

[jerryjerry05]

Re: Volvo AQ131A overheating

Fill out the profile so we know where you are from.Salt or fresh water can make a difference.The raw water pump on the engine is the only one nothing in the drive.
You probably need to replace the exhaust manifold.They corrode bad from setting.Take it off and check the end for clogging/rust/blocked holes.The interior really gunks up.Then check the intake ports for water/rust.
When the motor is reved up and water comes from the cap it's a sure sign the manifold is clogged.Jerry

 

[rteeng]

Re: Volvo AQ131A overheating

Thank you for the quick reply. I filled out my profile. I am in northern Wisconsin so fresh water only. However, the lakes here are full of thick algae in spots.

Is there a way to check flow through the manifold without removing it? The exhaust manifold is the one item I fear removing since I have a history of bolts breaking while trying to remove them? If I need to remove it then I can make an attempt at it.

I just recalled that when the boat was first put in the water there was quite a bit of water pumping out of a hole under the manifold. A plug wasn't put back in properly.

I am confused about your statement ...

When the motor is reved up and water comes from the cap it's a sure sign the manifold is clogged

The cap I am refering to is the main coolant tank cap. Aren't these systems separate?

 

[Maclin]

Re: Volvo AQ131A overheating

On the Volvo drives like yours (270 probably) there are some components on the drive itself that can affect how much water the raw water pump draws in.

There is a fitting on the intermediate housing on the drive right under the drive bellows that a hose connects to, the hose goes up thru the transom and feeds the raw water pump. The fittings have a tendency to corrode badly. This fitting is underwater when going slow but is out of the water when on plane. If the fitting or hose allows air to be sucked in then the raw water pump can cavitate and lose suction at speed.

Whe you run it in the tub this fitting is probably covered up as well just like it was in the lake.

Don S has a Volvo cooling system trouble shooting guide, hopefully he will see this soon and respond.

 

[jerryjerry05]

Re: Volvo AQ131A overheating

You should have 2 caps on the unit.1 for sea water strainer and the 2nd on the coolant side.Where was yours leaking?You didn't say it was leaking antifreeze.If it's the raw water side then it's probably the manifold.
Take the rubber hose off the end of the manifold and look for corrosion/rust blocked holes. If it's original equipment then it's way past due for a new manifold. Most Volvos have stainless inserts so the bolts shouldn't be too bad.
If you were in salt water the brass heat exchanger in the fresh water side might be clogged. It can clog with sand too.
I've worked on hundreds of these motors and the manifold is usually the culprit.Jerry

 

[rteeng]

Re: Volvo AQ131A overheating

Sorry about that! I forgot about the cap for the raw water filter. When it overheats the coolant is spraying from the 'radiator' cap. I hope to work on more yet tonight and give another update.

 

[Don S]

Re: Volvo AQ131A overheating

Do a cylinder leakdown test with the "Radiator" cap off. (That's heat exchanger cap for us marine folks ) if there is a leak between the cylinder and the antifreeze side of the cooling system, bubbles will appear in the coolant.

 

[rteeng]

Re: Volvo AQ131A overheating

I pulled all of the hoses off on the suction side of the raw water pump. The fitting on the intermediate housing was corroded but "seemed" like it was a good seal. It was very difficult to get off.

Don, When I ran it last night I had the heat exchanger cap off for a while so I could check for circulation. I did notice what looked like small air bubbles or foam. I didn't get alarmed when I saw it. I thought it was normal, kind of like foam you get when you shake something up. I take it this could be very bad news for me.

Sorry for all the ignorance. I am still a work in progress.

 

[Don S]

Re: Volvo AQ131A overheating

You will alwasys see some bubbles in a heat exchanger (or a radiator), it's just the nature of them. The circulating pumps are circulating the coolant, and any air in that coolant.
If you want to find where the air is coming from, do a leakdown test.
While you have a much older engine and drive setup than the link I am going to post, just look and think about all the similarities and the how's and why's in this VP Overheat diagnostic file.

http://www.4shared.com/account/file/50572185/e88f1d89/Volvo_Penta_Overheat_Diagnosis.html

 

[rteeng]

Re: Volvo AQ131A overheating

I wanted to update everyone on this issue. This spring I pulled the lower unit off and checked all the seals for the raw water suction line.

The plastic bushing in the intermediate housing (just under the hoes fitting) was extremely worn and sloppy. I just put in new seals, gaskets and hose fitting from a steering stem kit. Everything is nice and tight now.

I can't test it on the lake until all the ice has melted but it looks promising.

Thanks to all for you suggestions.
Tim

 

[captmello]

Re: Volvo AQ131A overheating

Good luck to you!

I'm battling a similar overheating issue with my motor. In fact I'm pulling my lower this weekend and resealing it.

You pulled yours off? Any words of wisdom? I've never had mine off but it seems straight forward.

Make sure you let us know how yours turns out. Looks like we're both going to be waiting a few weeks for the water test.