Blown head gasket - Rebuild or drop in used engine?

[scott-b]

Well, I believe I blew a head gasket on my 1.8T from my 2003 A4 with a manual and quattro. Leaking from the passenger side rear of the engine (previously replaced the rear flange and it doesnt seem to be leaking from there). Leaks been getting worse and then a few weeks ago the temps started rising- at first I just assumed it was because I hadn't filled the coolant reservoir to replace leaking fluid. I shut it down every time it got to the 3/4 mark and let it cool off.

Today it would heat up almost instantly to overheat. (both on the gauge and the ECU sensor). Odd thing is there is no coolant in oil and no oil in coolant. Pulling off the coolant reservoir cap and starting and running the engine wasn't blowing any coolant out as of yesterday, haven't tried it today yet. I've bled the air out of the system and it doesnt change the overheating.

So, assuming it is a head gasket I imagine a compression check should show low compression. I've got 207,000 miles on the car and I'm not sure if it's worth just doing the head gasket. Should I redo just that, rebuild the engine completely or replace with a used engine? I've built about 9 engines previously so I'm not afraid of the process, just the price.

[dalazybastard]

When was the last time the water pump was replaced?


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[maurizio]

Gasket + ARP Bolts (Assuming no other issues)=$
vs
Rebuild? Replace engine ? = $$

Im not sure i follow your logic

[B5carl]

Yeah why would you need to replace engine? just fix it!

[Kevin C]

How was your motor before the overheat? If it ran good and was not using oil fixing it is a cost effective option. The lowest cost option is to find a good running used motor for short money at a pick a part. Finding a good one is a bit of a gamble.

[ECS Tuning-Audi]

Chances are if you didn't overheat the engine too severely you should be able to just pop a new gasket on.

You'll need a new turbo to cat gasket, valve cover gasket, timing belt tensioner, head bolts, head gasket, and coolant at the bare minimum. If you haven't done a timing belt/water pump service it would probably be a good idea to go ahead and have it done since you have to remove the t-belt anyways.

Jason

[BARRY]

in the case of the 1.8t often it is cheaper and easier for the shop just to replace the headgasket and other related items.

for other engines like out of a BMW often it is cheaper to replace the entire engine.

it's a fine balancing act of cost vs history of reliability of that particular engine.

[DougL]

I'd replace the head gasket, but have your head checked and if it needs a $100-120 decking I would go for it.

I've replaced many head-gaskets and taken the gamble. Sometimes the motor wasn't overheated and warp, sometimes it was and you find out 5-10k later when you blow the new one.

It's cheap insurance. Not that the job is difficult but who likes to do things twice these days. Also get a turbo to manifold gasket and exhaust manifold gasket. Perfect time to do them.

[scott-b]

Thanks for the replies everyone. My reasoning was that with 207,000 miles on it maybe something else might let go if I just do the head gasket. It doesn't burn any oil (!), and hasn't had any other issues at all engine wise. Supposedly the timing belt was done 40K miles ago, but I wonder if they didn't replace the water pump at the same time. So perhaps just doing the head gasket (and other gaskets) and upgrading to ARP fasteners and doing the timing belt and water pump is a good way to go. I'll check the block and head for squareness when I pull it apart. Thanks again for the input.

[Kevin C]

Thanks for the replies everyone. My reasoning was that with 207,000 miles on it maybe something else might let go if I just do the head gasket. It doesn't burn any oil (!), and hasn't had any other issues at all engine wise. Supposedly the timing belt was done 40K miles ago, but I wonder if they didn't replace the water pump at the same time. So perhaps just doing the head gasket (and other gaskets) and upgrading to ARP fasteners and doing the timing belt and water pump is a good way to go. I'll check the block and head for squareness when I pull it apart. Thanks again for the input.

At 207,000 miles I would stick with stock headbolts. Aftermarket fasteners that have a higher clamping force will also increase cylinder wall distortion. That may or may not cause a problem with high millage rings, it certainly wont help how well they seal.

[19jdog]

Have the head resurfaced!! don't skimp out on this! Ask me how I know...

[rocket1420]

I would properly diagnose it first.

[scott-b]

Thanks everyone. Okay, so compression isn't great, but didn't immediatetly red flag as a blown head gasket Cylinder #1 at 140, 2 at 133, 3 at 135 and 4 at 150 (this is cold). That seems somewhat low, but not extremely indicative of a blown head gasket. Also, no bubbles in the coolant reservoir.

[scott-b]

After a lot of searches, it sounds like my symptoms are very similar to other people's issues with water pumps. The fact that my compression isn't totatlly out of whack and there was no typical residue on the plugs supports the head gasket being ok. I'll do a leakdown test in a few days and see. I think the coolant leak may be coming from the rear coolant flange which just happened to occur around the same time as the water pump issues.

[V70R]

Do you have access to a coolant system pressure tester? This would help locate the coolant leak without risking any further damage. Also, remove the upper timing cover (2 clips, and disconnect the G40 cam sensor before removal) and see if the pump appears to be replaced during the belt service.

[Gberg888]

I went to replace my head gasket last month and found a cracked head.

Luckily my friend had a 75 dollar head lying around so i bought that and had my shop put it all back together with a fluid damper, autotech intake cam, and timing job... $4k later I was running again...

My cam cap had cracked and the 75 dollar head had bad cams too. So we pieced everything back, had it all machined together. Had to get new lifters and guides though, I was told you need to replace those every time no matter what we rebuilding a head.

[tirefire]

I'm in the process of chasing down a coolant leak in a b6 with a 1.8t that I bought the other day. Thought I'd bring this back up to clarify a thing or two.

Shouldn't the OP have used a block tester to check for combustion gas in the coolant system to verify a BHG? I'm wondering because I tested mine and result was negative, but I suspect that the block tester tool isn't a totally reliable indicator. On my car, it wasn't able to draw any additional air into the expansion tank, meaning it only tested the air that was hanging out in there. Since the car is leaking coolant somewhere, shouldn't the tester be able to draw air into the system?

Sorry if this is wandering a bit.

[rocket1420]

I'm in the process of chasing down a coolant leak in a b6 with a 1.8t that I bought the other day. Thought I'd bring this back up to clarify a thing or two.

Shouldn't the OP have used a block tester to check for combustion gas in the coolant system to verify a BHG? I'm wondering because I tested mine and result was negative, but I suspect that the block tester tool isn't a totally reliable indicator. On my car, it wasn't able to draw any additional air into the expansion tank, meaning it only tested the air that was hanging out in there. Since the car is leaking coolant somewhere, shouldn't the tester be able to draw air into the system?

Sorry if this is wandering a bit.

A compression test is sufficient to determine whether a head gasket is blown.