Head Gasket Replacement AQ170C

[heryrg2711]

Hey guys. So a week ago i found water in oil. Took apart the head and found a head gasket with several cracks and some holes. Seems to be original, '76.
I took the head off cleaned it, took out some rust from the water channels, cleaned where the thermostat is with fire jelly, to remove some of the rust. Also cleaned the circulation pump. Getting ready to put everything back together.

My questions are:
Can i reuse the headbolts? They seem ok.
What grease/oil should i use on the bolts when putting them back in?
Should i use any silicone/sealant/grease on the gasket? Or just gasket onto block and then head onto that.

Also, i'm having trouble finding the thermostat for this engine, auto store one doesn't fit. I'm thinking of running it without the thermostat. I found a right size oring and a gasket that fits almost perfectly, to create that seal the thermo forms. What do you guys think?

 

[Don S]

Re: Head Gasket Replacement AQ170C

Here's a link to download the Volvo service manual for that engine. It should answer your questions.

http://www.4shared.com/file/59747156/6c065c44/AQ130_thru_170_Serv_Man.html

 

[heryrg2711]

Re: Head Gasket Replacement AQ170C

Thanks Don,
Per manual, doesn't say anything about new head bolts, so using the old ones.
Doesn't say to use any oil/lube when refitting the head. So none will be used.

Any thoughts on running without a thermostat?

 

[Don S]

Re: Head Gasket Replacement AQ170C

Any thoughts on running without a thermostat

You need a thermostat. If it overheats with a new thermostat, then there is a problem somewhere else, find it and fix it.

Removing a thermostat is only covering up the real problem, and is not fixing anthing.

 

[RogersJetboat454]

Re: Head Gasket Replacement AQ170C

Any thoughts on running without a thermostat?

Don't...
Get the proper t-stat. Sierra parts sold through NAPA should offer something, or dig deep and get the VP t-stat.

For the record,
Head bolts are re-usable. Head gasket should be installed dry.

Did you have the head checked for warping? My 170 blew it's head gasket, and was hydro-locking cylinder 2. I tried the hail-Mary fix of just throwing in a new gasket. Ran great for a while till that gasket blew... Head needed to be planed, and crack was found and fixed in cylinder 4 exhaust seat.

 

[NetDoc]

Re: Head Gasket Replacement AQ170C

Most head bolts from that era are expected to be reusable. DO NOT LUBRICATE them as this will cause an improper torque setting.

Head gaskets go on dry unless the manufacturer specifies otherwise and even then, its only on a small part of the gasket.

Please take the time to check the head and the block for warpage. Nothing is as frustrating as having to do this job twice! That being said, clean, clean, clean those mating surfaces. Use a wire brush on cast iron surfaces and careful scraping for aluminum ones. I have a flat edge that I skim one edge across the surface with a 0.0015 brass feeler to check for both cleanliness and warpage.

 

[Don S]

Re: Head Gasket Replacement AQ170C

Personally, I would be using oil on the head bolt threads. The manual for that particular engine is very minimal. For every Volvo engine gas and diesel except that group of engines, says to lubricate the threads. Engine Oil is all that's needed, and not dripping with oil. In diesel school, it was oil and let drain off before using.
Tap the threads in the block to make sure they are clean. A wire brush on the head bolts (Except some diesels) works great.

 

[heryrg2711]

Re: Head Gasket Replacement AQ170C

Thanks for the input guys. The head looks good, but i will check for warp, just need to find something super straight
The gasket looks nasty and corroded, like i said looks original, so i don't think it was a head problem, just old gasket.

About t-stat, the only problem i see without one is the motor will have water flowing through it from the get-go, cooling it when it's already cold. Once the motor is warm, the t-stat is always open anyways, because these motors run hot(i think). I want to go to the lake this weekend and also don't want to dish $70 on one when i can run without one.

BTW, when the manual says tighten the head bolt in 2 stages. This means that i tighten all the bolts in order to correct spec then tighten them more in order to the secondary spec, right?

 

[NetDoc]

Re: Head Gasket Replacement AQ170C

BTW, when the manual says tighten the head bolt in 2 stages. This means that i tighten all the bolts in order to correct spec then tighten them more in order to the secondary spec, right?

Yes, use the correct torque sequence both times. usually the first is to about %70 of the total torque.

And please, unless directed to by your manufacturer, DON'T OIL THE THREADS. 30 years in automotive, and I know of only two engines that asked for that. Neither of them were gasoline powered.

 

[RogersJetboat454]

Re: Head Gasket Replacement AQ170C

Thanks for the input guys. The head looks good, but i will check for warp, just need to find something super straight

Yep, a machinists strait edge. Nothing else will do. Never met anybody who could see thousands of an inch difference with the naked eye.

The gasket looks nasty and corroded, like i said looks original, so i don't think it was a head problem, just old gasket.

If the head was being clamped evenly, the only area of the gasket that may look nasty and corroded is the areas that seal around the water jackets. Honestly, I would pay the short money for a machine shop to professionally check for warping, and pressure test the head. It's a whole lot cheaper then buying another gasket set if this one fails.

About t-stat, the only problem i see without one is the motor will have water flowing through it from the get-go, cooling it when it's already cold. Once the motor is warm, the t-stat is always open anyways, because these motors run hot(i think). I want to go to the lake this weekend and also don't want to dish $70 on one when i can run without one.

Other problems too... The combustion process isn't going to be as efficient, because the engine is colder than it should be. Power may be down. You are more likely to have cylinder wash down with the unburnt fuel, which will contaminate the oil, and cause pre-mature wear on the cylinders. The engine will not be able to get the oil up to full temp, so any moisture and hydrocarbons in the oil will not burn off, and be more likely to form acid that is bad for bearings. Your plugs are more likely to foul.

The T-stat IS NOT always open when it's warm. The T-stat cycles open an closed maintaining it's pre-determined temp. When the engine warms up, the t-stat opens, allowing the hot water to be dumped, and cold water to enter the engine. When the cold water enters, the t-stat closes and the water heat's up again. My 170 runs at a constant 160?F. When the engine is cold, it can run like S***. The t-stat is available here on Iboats for $58;http://www.iboats.com/mall/partfind...gd_poid=111063&gd_row=32&**********=533466556

BTW, when the manual says tighten the head bolt in 2 stages. This means that i tighten all the bolts in order to correct spec then tighten them more in order to the secondary spec, right?

That is correct. You do this so the cylinder head clamps down to the block evenly. After a run, re-check to torque of the head bolts.

 

[heryrg2711]

Re: Head Gasket Replacement AQ170C

Thanks Rogers.
I see what you're saying and probably will order a tstat today, maybe skip boating
The replacement t-stat is rated for 55c, only 130f. After the motor is thoroughly warmed up, do you really think the temp will often drop below 130?
Although i am in CO where the water is cold, but no less then 50F when boating, i would think.

 

[RogersJetboat454]

Re: Head Gasket Replacement AQ170C

Thanks Rogers.
I see what you're saying and probably will order a tstat today, maybe skip boating
The replacement t-stat is rated for 55c, only 130f. After the motor is thoroughly warmed up, do you really think the temp will often drop below 130?
Although i am in CO where the water is cold, but no less then 50F when boating, i would think.

The temp should stick to around 130-140?F. This is why you need a t-stat. With an operating t-stat, it really doesn't matter what the temp of the incoming water is. If the water is colder, the T-stat won't be open as long. If the water is warmer, it will be open longer.

Since you are in fresh water, you could cheat and use an auto t-stat. Problem is, the lowest temp I found on Rockauto.com is a 180?F t-stat. I wouldn't use a t-stat that runs any hotter than 160-170 as these B30's tend to be pretty hot blooded in a marine environment.

 

[heryrg2711]

Re: Head Gasket Replacement AQ170C

The lowest one i found was at orielys rated for 160.
The motor calls for 130 so i think 160 is a bit hot.
I just placed the order for a tstat so i should be good now.
Thanks for the help.